Growth within Planetary Boundaries I

The nine planetary boundaries


Stratospheric ozone depletion

The stratospheric ozone layer in the atmosphere filters out ultraviolet (UV) radiation from the sun. If this layer decreases, increasing amounts of UV radiation will reach ground level. This can cause a higher incidence of skin cancer in humans as well as damage to terrestrial and marine biological systems. The appearance of the Antarctic ozone hole was proof that increased concentrations of anthropogenic ozone-depleting chemical substances, interacting with polar stratospheric clouds, had passed a threshold and moved the Antarctic stratosphere into a new regime. Fortunately, because of the actions taken as a result of the Montreal Protocol, we appear to be on the path that will allow us to stay within this boundary.

Loss of biosphere integrity (biodiversity loss and extinctions)

The Millennium Ecosystem Assessment of 2005 concluded that changes to ecosystems due to human activities were more rapid in the past 50 years than at any time in human history, increasing the risks of abrupt and irreversible changes. The main drivers of change are the demand for food, water, and natural resources, causing severe biodiversity loss and leading to changes in ecosystem services. These drivers are either steady, showing no evidence of declining over time, or are increasing in intensity. The current high rates of ecosystem damage and extinction can be slowed by efforts to protect the integrity of living systems (the biosphere), enhancing habitat, and improving connectivity between ecosystems while maintaining the high agricultural productivity that humanity needs. Further research is underway to improve the availability of reliable data for use as the ‘control variables’ for this boundary.

Chemical pollution and the release of novel entities

Emissions of toxic and long-lived substances such as synthetic organic pollutants, heavy metal compounds and radioactive materials represent some of the key human-driven changes to the planetary environment. These compounds can have potentially irreversible effects on living organisms and on the physical environment (by affecting atmospheric processes and climate). Even when the uptake and bioaccumulation of chemical pollution is at sub-lethal levels for organisms, the effects of reduced fertility and the potential of permanent genetic damage can have severe effects on ecosystems far removed from the source of the pollution. For example, persistent organic compounds have caused dramatic reductions in bird populations and impaired reproduction and development in marine mammals. There are many examples of additive and synergic effects from these compounds, but these are still poorly understood scientifically.  At present, we are unable to quantify a single chemical pollution boundary, although the risk of crossing Earth system thresholds is considered sufficiently well-defined for it to be included in the list as a priority for precautionary action and for further research.

Climate Change

Recent evidence suggests that the Earth, now passing 390 ppmv CO2 in the atmosphere, has already transgressed the planetary boundary and is approaching several Earth system thresholds. We have reached a point at which the loss of summer polar sea-ice is almost certainly irreversible. This is one example of a well-defined threshold above which rapid physical feedback mechanisms can drive the Earth system into a much warmer state with sea levels metres higher than present. The weakening or reversal of terrestrial carbon sinks, for example through the on-going destruction of the world’s rainforests, is another potential tipping point, where climate-carbon cycle feedbacks accelerate Earth’s warming and intensify the climate impacts. A major question is how long we can remain over this boundary before large, irreversible changes become unavoidable.

Ocean acidification

Around a quarter of the CO2 that humanity emits into the atmosphere is ultimately dissolved in the oceans. Here it forms carbonic acid, altering ocean chemistry and decreasing the pH of the surface water. This increased acidity reduces the amount of available carbonate ions, an essential ‘building block’ used by many marine species for shell and skeleton formation. Beyond a threshold concentration, this rising acidity makes it hard for organisms such as corals and some shellfish and plankton species to grow and survive. Losses of these species would change the structure and dynamics of ocean ecosystems and could potentially lead to drastic reductions in fish stocks. Compared to pre-industrial times, surface ocean acidity has already increased by 30 percent.  Unlike most other human impacts on the marine environment, which are often local in scale, the ocean acidification boundary has ramifications for the whole planet. It is also an example of how tightly interconnected the boundaries are, since atmospheric CO2 concentration is the underlying controlling variable for both the climate and the ocean acidification boundaries, although they are defined in terms of different Earth system thresholds.

Freshwater consumption and the global hydrological cycle

The freshwater cycle is strongly affected by climate change and its boundary is closely linked to the climate boundary, yet human pressure is now the dominant driving force determining the functioning and distribution of global freshwater systems. The consequences of human modification of water bodies include both global-scale river flow changes and shifts in vapour flows arising from land use change. These shifts in the hydrological system can be abrupt and irreversible. Water is becoming increasingly scarce – by 2050 about half a billion people are likely to be subject to water-stress, increasing the pressure to intervene in water systems.  A water boundary related to consumptive freshwater use and environmental flow requirements has been proposed to maintain the overall resilience of the Earth system and to avoid the risk of ‘cascading’ local and regional thresholds.

Land system change

Land is converted to human use all over the planet. Forests, grasslands, wetlands and other vegetation types have primarily been converted to agricultural land. This land-use change is one driving force behind the serious reductions in biodiversity, and it has impacts on water flows and on the biogeochemical cycling of carbon, nitrogen and phosphorus and other important elements. While each incident of land cover change occurs on a local scale, the aggregated impacts can have consequences for Earth system processes on a global scale. A boundary for human changes to land systems needs to reflect not just the absolute quantity of land, but also its function, quality and spatial distribution. Forests play a particularly important role in controlling the linked dynamics of land use and climate, and is the focus of the boundary for land system change.

Nitrogen and phosphorus flows to the biosphere and oceans

The biogeochemical cycles of nitrogen and phosphorus have been radically changed by humans as a result of many industrial and agricultural processes. Nitrogen and phosphorus are both essential elements for plant growth, so fertilizer production and application is the main concern. Human activities now convert more atmospheric nitrogen into reactive forms than all of the Earth’s terrestrial processes combined. Much of this new reactive nitrogen is emitted to the atmosphere in various forms rather than taken up by crops. When it is rained out, it pollutes waterways and coastal zones or accumulates in the terrestrial biosphere. Similarly, a relatively small proportion of phosphorus fertilizers applied to food production systems is taken up by plants; much of the phosphorus mobilized by humans also ends up in aquatic systems. These can become oxygen-starved as bacteria consume the blooms of algae that grow in response to the high nutrient supply. A significant fraction of the applied nitrogen and phosphorus makes its way to the sea, and can push marine and aquatic systems across ecological thresholds of their own. One regional-scale example of this effect is the decline in the shrimp catch in the Gulf of Mexico’s ‘dead zone’ caused by fertilizer transported in rivers from the US Midwest.

Atmospheric aerosol loading

An atmospheric aerosol planetary boundary was proposed primarily because of the influence of aerosols on Earth’s climate system. Through their interaction with water vapour, aerosols play a critically important role in the hydrological cycle affecting cloud formation and global-scale and regional patterns of atmospheric circulation, such as the monsoon systems in tropical regions. They also have a direct effect on climate, by changing how much solar radiation is reflected or absorbed in the atmosphere. Humans change the aerosol loading by emitting atmospheric pollution (many pollutant gases condense into droplets and particles), and also through land-use change that increases the release of dust and smoke into the air. Shifts in climate regimes and monsoon systems have already been seen in highly polluted environments, giving a quantifiable regional measure for an aerosol boundary. A further reason for an aerosol boundary is that aerosols have adverse effects on many living organisms. Inhaling highly polluted air causes roughly 800,000 people to die prematurely each year. The toxicological and ecological effects of aerosols may thus relate to other Earth system thresholds. However, the behaviour of aerosols in the atmosphere is extremely complex, depending on their chemical composition and their geographical location and height in the atmosphere. While many relationships between aerosols, climate and ecosystems are well established, many causal links are yet to be determined.


Growth within Planetary Boundaries V

The Case of Population

We’re in search of a sustainable development trajectory for the planet. We want to help countries grow, especially the poorest countries, to break free of the poverty trap. We need to respect planetary boundaries, and we want growth to be fair, widely shared with a broad inclusive prosperity. We’ve seen how hard this is going to be, whether it’s the energy system, or the food production technologies that are going to have to change markedly. But a big part of the challenge, the extent of the challenge, the ability to meet sustainable development will depend on the future of population dynamics.

The more people there are on the planet, the more mouths to feed, the more challenges there will be to reconcile the economic objectives of rising living standards per person, multiplied by a larger number of people, and respecting the planetary boundaries. And so, facing the question of population is key. We also know it’s key for inclusiveness and breaking free of poverty. Because when poor families have large numbers of children, they are not able to provide the kind of investment in the human capital, as we call it. Meaning the health, the nutrition, the education, the skills of their own children. In order to ensure that they are productive and meet their their potential is, as adults. And so, reducing the fertility rates, voluntarily, respecting human rights and family desires to levels that are low enough to foresee a stabilization, even a gradual decline of today’s large population, or the one that we will have on the planet in the future, will make it easier to achieve the other aspects of sustainable development as well. Social inclusion, ending extreme poverty. And of course as I’m emphasizing, respecting the planetary boundaries. So where do we stand?

Well, if we go back to Thomas Robert Malthus in 1798, a world of 8 to 900 million people. And he warned us, be careful, populations will grow. They have grown maybe by a factor of nine or ten, since Malthus gave us that famous warning, to 7.2 billion today. And that 7.2 billion today is up from around 2.5 billion people in the middle of the 20th century. You’re looking at a very pertinent set of scenarios, four of them shown here, produced by the United Nations Population Division. Notice that the solid line shows the actual change in population from 2.5 billion to 7.2 billion between 1950 and 2010. And then the four lines diverge, depending essentially on alternative assumptions about fertility rates, out to the end of the 21st century, to the year 2100. What are these four scenarios? The medium scenario shown here, it’s the one that is third from the top on the right hand side, reaching about 10.8 billion people in the year 2100. It’s called the medium fertility scenario of the UN Population Division. It’s the one we tend to look to as something like a continuation of current trends. That scenario shows us having an increase of another 3.6 billion people between now and the end of the century. What an enormous increase. That’s the middle scenario. Now at the top is something unthinkable, unimaginable, but very interesting for us. Suppose fertility rates do not come down at all, and for each age and each country in the world, the age specific child bearing tendencies continue into the future without reduction. Well, simply running the clock forward, based on the current fertility rates, the world population would soar well past 20 billion, 25 billion. In fact, by 2100, it would be 28.6 billion, four times higher than now. Impossible.


The Earth couldn’t manage it, but it does tell us something. It tells us that the medium scenario of the United Nations isn’t exactly business as usual in a mere continuation of current trends. It builds in the assumption already of a significant decline of fertility rates in future years. Take that into account. Because if those fertility rates do not come down, then 10.8 billion is going to look awfully optimistic in terms of where the population would settle, where I’m using the term optimism to mean keeping it on the lower side, so that we can envision realistically sustainable development. A constant fertility rate continuing exactly what’s happening right now, 28 billion people.

The next line down is what’s called the high fertility rate. It’s a little bit more plausible, pretty frightening. It says, if, instead of that medium scenario, women were to have just, on average, one half child more. So that each woman, instead of having two children, would have two and a half children or, or to put it another way, every ten women would be having 25 children rather than 20 children. Would mean billions and billions of people more on the planet. That’s how sensitive the population forecasts are to the future dynamics of fertility. We could reach 16.6 billion that is more than 5 billion in addition to the forecast of 10.8 billion, obviously. Now if rather than the medium fertility forecast, which has a built in estimated decline of fertility gradually over time, the decline of fertility were a bit faster. So that women were having on average a half child fewer than in the medium forecast, or every ten women having five children fewer than in the medium forecast. Then the world population would actually peak around mid century, and gradually decline to about 6.8 billion at the end of the century. From my point of view, that’s most attractive if we aim for sustainable development, which we presumably are aiming for. Because if we can have a peak of the world population, then a gradual decline, it’s going to be much easier to meet the inclusiveness goals, the fairness. It’s going to be much easier to meet the environmental objectives and needs as well. What this shows is that small changes of fertility rates will have big changes of outcomes. And it suggests that if steps are taken to help facilitate a faster reduction of fertility by, for example, keeping young girls in school rather than having them married, as in traditional societies at the age of 14 or sometimes even younger. This could make a very big difference.


Now, the next graph shows the annual rate of change of population in the medium scenario, but for different groups of countries. This is also important. The solid line third from the top, is the world average. What you see is that the population growth of the world peaked at about 2%, around 1970. At that time, the world population was on the order of about 4 billion people, which means that at a 2% growth rate, the world was adding about 80 million people per year.

Now if you fast forward to the year 2010, the growth rate is a little over 1% per year, 1.1 to 1.2% per year. But now, the base on which that percentage growth is occurring is twice as large as back in 1970. It’s now 7.2 billion people, multiply 1.1% by 7.2 billion people, or 1.2% by 7.2 billion people. Lo and behold, you’re getting about the same 80 million increase as of 40 years ago. This says that the proportionate growth rate of population has slowed. But the absolute numbers, the arithmetic increase year by year remains around 75 to 80 million people added to the world’s population each year. In the medium scenario, that growth rate tends to decline. It declines to almost zero by the end of the century, because fertility rates basically come down to replacement. Replacement fertility rate means that each mother has two children, one is a daughter, one is a son. Each mother is replacing herself with a daughter who will become the mother of the next generation. And keeping the numbers, therefore, in the long-term stable.

So since the fertility rate is assumed by the United Nations to trend towards the replacement rate of around two, the population growth rate also tends to converge to around zero. But what you see on this graph is that the least developed countries ironically, but not unexpectedly, have the highest population growth rate. Those are the places where family planning is not used. Those are the places where girls drop out of school early. Those are the places where women face massive discrimination. They’re not in the labor market, and so the opportunity cost of their time is low. They’re supposed to be home having children, according to the prevailing social norms, or maybe the desires of their husbands. Maybe not their own desires in many places, but traditional societies impose, through cultural and other means, that kind of pressure for large numbers of children.

Well, to see where fertility rates are right now, we can look at the next graph, which measures the actual fertility rates up to the year 2010.


And then shows the projections of the United Nations in this medium fertility projection for different groups of countries out to the year 2100. What you see is that, as of 2010, the countries at the bottom of this curve, which are the more developed, or the developed regions of the world, are already below replacement rate. If they continue with that fertility rate for another couple of generations, the population size will begin to decline in the high income world. The highest fertility rates in the curve at the very top of this picture are the least developed countries. Whereas, in 2010, still the total fertility rate is above four. Each mother, on average, is having two daughters. That means the population is tending to double, generation by generation. because each mother is replacing herself statistically with two daughters, who will grow up to be two mothers of the next generation. That’s why the population growth remains so high. And one can see in this graph, is that for the less developed regions as a whole and for the world on average, the fertility rates are a bit above replacement, but not as high as in the least developed countries. And therefore, on average, the population growth rate is less than it is in the poorest countries, but higher than it is in the high income countries.

Well, what could lead to a faster transition to a stable population, and to a replacement fertility rate? We know through observation and careful study that there are many key determinants of the fertility rate, of the fertility choice. Let me mention some of them.

First, age of marriage. In traditional societies, girls are often not schooled at all, or pushed out of school early. And married very early, maybe by the command of their father, who marries the girl for economic reasons within the community, or traditional reasons at the age of 12 or 14. And then childbearing starts very soon thereafter. And these young girls, who remain illiterate throughout their lives without economic, political, or social empowerment, often end up with seven or eight or nine children. So that is one determinant.

A second, obviously, is access to contraceptions and family planning. Places where contraceptives are widely available, where clinical services work, where there is good culturally sensitive advising where women can discreetly gain access to their contraceptive desires, tend to have lower fertility rates. And family planning programs that are, again, culturally sensitive and aware, and operating effectively in low income countries, can dramatically lower, on a voluntary basis, the total fertility rates in those countries.

A third determinant is the woman’s role in the labor force. In some countries, women aren’t allowed to work, or they’re not allowed to work outside the home, or they’re not allowed to work in many occupations. They face massive legal and social discrimination, or cultural practices that basically keep them at home. Now, raising children takes a lot of time. And therefore, if a woman is earning a living in the labor market, the cost of raising children, in terms of the lost wage income, can be very, very high. That means women that are in the labor force and are working and have that opportunity tend to want to have fewer children, because the opportunity cost of raising children is really quite high in terms of lost income. Women who face massive discrimination and aren’t allowed in the labor force may end up with more children, in part because of the market value of their time is so low. Not because it couldn’t command a higher income, but it’s not allowed to because of gender discrimination.

Another major factor is the urban versus rural location of families. Children are often farm assets. They do work, they do chores, they milk the cows, they carry fuel wood, they carry water. They therefore are not seen as a high cost, but actually as part of the farm labor for a family farm. In the urban areas, the child, much more likely, is going to school, but not working in a formal way. Typically, not always. There are painful exceptions. But this means that, on average, families in rural areas see the cost of raising children to be lower, because they see even young children being economic inputs to the household production. Whereas that’s not the case in urban areas. When families move to urban areas, their fertility rates come down.

Child survival is another key determinant. If it’s with the good reliability that the children will survive, families choose to have fewer children. If there’s worry about whether children are going to survive, many risk-averse households will have many, many children to compensate for the expectation that some of the children will die. So one of the keys to a quick voluntary reduction of fertility is to help keep children alive. Good public health, good health facilities in the local community.

The legality of abortion also plays an evident, a quite significant role statistically, different societies have different views. But those that have legalized abortion tend to have lower observed fertility rates than those where abortion is illegal. Still often undertaken, sometimes in very, very dangerous conditions. But where abortion is legalized, fertility rates tend to be lower.

The public leadership plays a big difference, because these are culturally determined phenomenon. Some places in traditional societies when families were on the farm, when children were dying in large numbers, the cultural norms were, have as many children as possible. But when conditions change, children are surviving, families are in urban areas, children need to be educated. Farm sizes have already shrunk, ecological burdens are high.  And you want a lower fertility rate as a result by giving the options and awareness to households. Then the political leadership’s saying, you know, for your good, your farm size has shrunk. You’re trying to help raise children with good education, have fewer children. The political leadership and the public awareness can play a huge role. As, of course, do the role models that people see. One of the things sociologists have found is that when television sets come into a poor rural area, fertility dmnaterates tend to come down. The hypothesis, at least, is that people are observing on their television shows, in their sitcoms and and in, in their soap operas, families with fewer children. And in the rural areas, that’s giving the idea that there’s only one son or daughter, maybe two children, not six or eight. And that changes the social norms as well. This is a big deal for us.

The dynamics of the world will look very different if the world population reaches 11 billion at the end of the century versus stabilizing, and even falling gradually below 7 billion. The latter would be much easier from the point of view of quality of life, income per capita, and environmental sustainability. And there’s good reason to believe it would be the preferred choice of households if they have access to family planning, education for their girls, child survival, jobs, and an absence of discrimination for women. Provide those conditions, most likely households will absolutely take the opportunity on a voluntary basis for a sharp reduction of fertility rates, helping to move the world more quickly to a peaking and stabilization, and then gradual decline of the world population thereafter.

Growth within Planetary Boundaries IV

The Case of Food

You would think, I think intuitively that energy would be the dominant way that humanity is impacting the planet. We’ve just seen how massive energy use translates into rising carbon dioxide and climate change. And energy, of course, is everywhere in our transport systems, our power supplies, our industrial processes, our home use. But it’s quite arguable I would say it is right to say, that the agriculture sector has an even larger impact on the physical planet and the various earth systems than energy. Energy is causing climate change. Agricultural use and agricultural patterns not only have a huge impact on climate but have a huge impact on every aspect of the Earth’s systems and the planetary boundaries.

We’ll see soon that the food production contributes massively to greenhouse gas emissions, therefore to climate change. But we’ll see also that the energy system as we go around the the circle is in a way dwarfed by the food production system in its impacts on each of the other areas of the, the planetary boundaries. The nitrogen and phosphorous cycles, where we get the pollution from the runoff of nitrogen and phosphorus-based fertilizers. The fresh water use, which is about 70% used in the agricultural sector. The change of land use overwhelmingly a reflection of agriculture. The loss of biodiversity  coming from the way that farmlands and  pasture lands and and tree crop plantations absolutely threaten habitats of other species unless uh,agriculture is done in an agro-ecologically friendly manner. Chemical pollution with the heavy application of chemicals such as herbicides and pesticides used in agriculture. There’s a tremendous amount of chemical impact from the farm system. So it is quite arguable that farming dominates the all of the human activities in terms of the anthropogenic effects. Anthropo, human. Genic, caused by. That is the various human-caused impacts on the planet.

Now this is in a way ironic because it takes us right back to the beginning of the modern economic era and to the very beginning of economic studies just like Adam Smith does and just like Adam Smith’s wisdom is still useful today, so too is that of another great thinker Thomas Robert Malthus who wrote famous text in 1798 called Principles of Population. Malthus was afraid. He was also afraid of planetary boundaries, but for a slightly different reason. Malthus said that the human population has a tendency to rise at a geometric rate. And so if left on its own with the basic needs met the human population would continue to expand rapidly. He was right in that when he wrote the Principles of Population in 1798. The total population may have been 800 million, maybe 900 million. Roughly one tenth of the level that it is today. So Malthus was right that human population tends to increase markedly, at a geometric rate he said. Now, he feared that the ability to grow food would only increase at an arithmetic rate. That is adding a certain number of tons of feed grain or food grain per year to the world’s capacity to grow food. And Malthus said, look, any geometric growth will always overtake any arithmetic growth. So the growth of the human population is always going to overtake the ability to grow food, he said. And at some point there will be so many people that hunger will ensue. And when hunger ensues there will be various kinds of devastating feedbacks whether it’s war, whether it’s famine, whether it’s disease or other scourges that will push population back down. But will mean that humanity won’t break free of the physical constraint on the ability to grow food.

Now Malthus did not anticipate the scientific advances of the Green Revolution, for example. He didn’t anticipate modern seed breeding of course even Mendel who invented the modern science of genetics would come basically about three quarters of a century after Malthus. Malthus also didn’t anticipate the breakthroughs in the science of soil nutrients and the use of chemical fertilizers to replenish soil nutrients and to boost food yields. Nor did he anticipate at least the potential for the human potential to stabilize by means of modern contraception, family planning, and choices that households make. So Malthus, couldn’t see the full dynamic ahead, but he worried that the human population would outstrip the carrying capacity of the planet itself. For a long time, economists and others laughed at Malthus. They said, you’ve got it all wrong. You see modern science allows us to grow enough food for a geometric rise of the population. We know how to add fertilizer, we know how to have high yield seed varieties. But, you know, Malthus’ a pretty clever guy and he had a real insight and we’re not done with his story yet because his warning rings true today.While it is the case that increases of food production technology in agronomy and food processing, storage, transport and the ike has made it possible to feed 7.2 billion people though not all of them by any means fed well or nutritiously. It is also the case that the food production system is so destructive of the environment that Malthus is still there, waving his finger saying not so fast. You haven’t proven that you can grow this amount of food sustainably.

What’s going to happen when the water runs out? What’s going to happen when the nitrogen and phosphorus loadings become so large and so forth. So I would say we’re not at the end of the Malthusian story yet. Sustainable development calls for a renovation, a reform, an upgrading of the technological systems to grow food. It calls for us to eat more wisely as well. Eating the kinds of food products that don’t threaten the natural environment. For example, not eating endangered fish species or endangered species of land mammals. Unfortunately some of which are in huge supply as delicacies, even to the point of illegal hunting and poaching and threatening the very survival of these species. So, changing farm systems and changing human behavior, in terms of our diet and use of agricultural products, is possible. But in order to meet Malthus’s challenge, we still have to prove that it’s possible to grow food in a sustainable manner

For all of the people properly nourished on the planet, and with the food system recognizing and respecting the planetary boundaries. Boy, are we far from this today. Let’s think about some of the ways that the food system is impinging on the planetary boundaries.

First, the food system is an enormous source of greenhouse gases. Of course agriculture uses a lot of energy. For planting, for harvesting, for storing, transforming and transporting food and other agricultural commodities. There’s a lot of energy stored in chemical fertilizers, because to make urea, or other nitrogen based fertilizers, one requires a lot of energy to create the chemical compounds in those fertilizers. But what’s interesting and important for us to note, is that agriculture emits greenhouse gases in other ways as well. Remember, the two other major greenhouse gases, anthropogenically caused, that is, caused by human beings in addition to CO2 are methane and nitrous oxide. Now methane or CH4 is emitted in a variety of ways. It’s emitted by anaerobic processes in flooded or paddy field rice for example. Where the metabolic processes of the bacteria release methane into the atmosphere. It’s also released from the gut of ruminant livestock. When cows chew their cud, and digest their food they are also emitters of methane on, on a large scale. Nitrous oxide is emitted partly through industrial processes and electricity production at coal fired power plants. But it’s also emitted by the chemical decomposition of nitrogen based fertilizers. So fertilizers are a source of nitrous oxide in the air.

But they’re also a source of water pollution in the sea. In both cases, the nitrogen is supplied on the farms, but it’s not taken up by the plants themselves. It either volatilizes into the atmosphere or it runs off into the water and then, on the way through the rivers and ground water to the ocean. So greenhouse gases is one major way that that the agriculture system impinges causing climate change. Land use change and habitat loss is another obvious way. Humans use land primarily, not for our cities, not for our highways, but for our farms and our pasture land and our timber land. And we have already taken hold of so much land, so much photosynthetic potential, to feed us, that we’re depriving other species, not only of their natural habitats, but of the food that they need to stay alive. And that’s why we’re driving numbers of other species down sharply. Agriculture, as I mentioned earlier, is a major source of chemical pollutants often very long lasting and very toxic chemicals that are used as pesticides and as herbicides and as other parts of the food production chain.

Agriculture has another perverse threat which is called invasive species. Invasive species means that humanity advertently, or inadvertently, but generally unwisely takes a species from one part of the world, puts it into another environment, perhaps where there’s no competition with that species. If it’s an animal, it can run wild. If it’s a plant or a weed, it can take over a a land area, or a lake for example, dominating the local biodiversity. Invasive species means that we are rearranging the biogeography. The places on the planet where various species exist. And we’re putting lots of species at risk by invading ecosystems where they don’t belong, where they are not native. Perhaps where they have no predators, or where they can invade and take over a lot of the resources of that ecosystem.

Nitrogen and phosphorus runoff, I’ve already mentioned. And look at this picture. The shocking picture off the coast of China there is so much fertilizer being used by Chinese farmers because it’s heavily subsidized, and because of bad farm practices that that fertilizer runs off the farms into the rivers and ground water. It accumulates in the estuaries and off the coast, and it creates this kind of algal bloom. And algal bloom means that there’s such a sudden massive loading of nutrients, nitrogen and phosphorus in particular that the algae which either naturally grows in a particular place or has been introduced say by fisheries practices, suddenly has this massive feast of nitrogen and phosphorous. And there’s an explosion of the amount of algae. This algae will die. Then it will be decomposed by bacteria. As those bacteria feast on the algae, the dead algae, they will be respirating, and they’ll be using a lot of the oxygen in the water. They will deplete the oxygen as part of the respiration process and by depleting the oxygen they will create an oxygen depleted zone of coastal waters. That’s called a hypoxic zone, low oxygen hypo oxia. And low oxygen kills the fish, kills the other species. Suddenly you have what ecologists and marine biologists call a dead zone. There are dead zones all over the coastal world now, especially in the estuaries.

Estuaries where the freshwater of rivers meets the saltwater of the oceans are wondrous ecosystems. Our shellfish and many other species are often indigenous to those locations, and they’re being threatened by this nutrient loading. By the utrification and then by the hypoxia that results. Creating dead zones and hypoxic regions in more than 130 estuaries around the world. The food system also gives rise to new pathogens. When we have the industrial breeding of poultry, for example, all crowded together, we have learned that there is recombination of genes of bacteria and viruses. When livestock and poultry out in the open mixed with the wild with the wild species of geese and other species, you get further recombinations. And this has given rise to many  emerging infectious diseases, some of which are very, very  frightening, like SARS. Was and remains very, very frightening. And so we have new and emerging diseases coming from industrial agricultural practices. Of course we have massive overharvesting, overhunting, overgrazing,over abstraction and cutting down logging of trees and forests. Most of the world’s major fisheries have been massively over fished.

In the Northeast of the United States where I live there was a collapse of the cod fisheries because of the massive amount of fish that was being hauled up using modern technologies trawlers and other high tech ways to fish a massive amounts of fish under the ocean.

And of course with all this food production we are using up water supplies through ground water depletion, through the diversion of rivers which no longer make it all the way to the sea. And the growing water crisis is extraordinarily frightening.

We see water scarcity as a major threat to well being, to human health, to economic development in many, many parts of the world adding climate change on one side, overuse of water coming from agriculture it’s quite a dangerous brew. So just as we are going to need to find a new pathway for energy basedon energy efficiency and low carbon energy supplies. We are going to need to find a new farm system, or I should say farm systems. Because there are farm systems distinctive all over the world depending on the local climates, local cultures, local soils, local ecological conditions. But what is nearly common to all of the major regions is that our farm systems are not yet sustainable.

We still have to prove Malthus wrong, we still have to take a tip from Malthus that the challenges of food supply are a major and continuing challenge facing humanity, and a core part of any agenda of achieving sustainable development.

Growth within Planetary Boundaries III

The Case of Energy

Of all of the problems of reconciling growth with planetary boundaries probably none is more urgent and none is more complicated than the challenge of energy. Remember that the whole world economy grew up, starting with the steam engine, then the internal combustion engine, the gas turbine as a fossil fuel built world economy. Fossil fuels, coal, oil, gas, have been our friend. They have been the basis on which the modern world has been built. And indeed until James Watt in 1776 came along with his steam engine, there was no way to even think about sustained economic progress. Where would the energy for industry come from? Every time industry would start to develop in the pre-steam engine age, so many trees would be chopped down to feed the boilers that the limits of industrialization were very quickly reached. It was fossil fuels that allowed the breakthrough to the era of modern economic growth. I emphasize this because that history reminds us of how deep the challenge is. Right now fossil fuels are not our friend because when coal, oil, or gas is burned the carbon that is the basis of those fossil fuels combines with oxygen and produces CO2, carbon dioxide, which is emitted into the air, which is the main greenhouse gas warming the planet, changing the climate, and endangering humanity and other species. And so what has been the key at the very core of the world economic growth is now at the core of our major problem. Well, you might say use less energy, but it’s not so simple.

Because as a physicist will remind us, what is energy? Quality energy is the ability to, to work. Any useful work in, in economy depends on energy. Sure, we waste a lot of energy in the form of release of heat or friction or driving cars much larger than they need to be or poorly insulated buildings. So energy efficiency is clearly part of any solution for sustainable development. But the world needs energy resources, will use energy resources, and the use of energy, even with a substantial gain of efficiency, is likely to increase in the aggregate as the world economy expands by factor three or by factor four as we have just seen. And so we have a problem. More energy is needed. The traditional forms of energy, the fossil fuels of coal, oil, and gas, can’t do it for us because that would create a massive intensification of the climate change problem. How big of an intensification?


That’s what I’d like to discuss, so that we get some parameters of where we are and where we’re going. This graph shows again on a logarithmic scale on the horizontal axis and on the vertical axis the income of different countries and the primary energy use of those countries, the energy consumption. Total energy use by country would include the fossil fuels, it might include wood burning, hydroelectric power, geothermal energy, wind and solar power, nuclear power or some other forms for instance biofuels. And what is done in this graph is for every country in the world to measure first the total output measured as the gross domestic product, and then to compare that with the total primary energy use. Which can be expressed in a number of ways, in units of kilowatts, or kilowatt hours, it can be expressed in tons of oil equivalent energy where, you take the amount of energy in one ton of oil, and then for all the other kinds of energy, whether it’s coal or gas or hydro and so forth, you look at the amounts of, of energy available from that resource and convert it as if it were tons of oil that had that much energy potential. And then express all the different energy sources with these conversion factors as a tons of energy equivalent amount of primary energy use. What you see when you graph the total output of an economy versus its energy consumption is essentially a straight line, though of course the countries don’t fall exactly on this upward sloping line. What this line signifies is that a doubling of the size of an economy tends to be associated with a doubling of primary energy use. Energy use scales alongside in proportion and in relatively constant ratio with total size of the economy. So, as the economy grows the energy use will tend to grow along side it. Save for break those in technology that allow for greater energy efficiency.

Lets look quantitatively at how much energy we use and what that implies for how much carbon dioxide we therefore emit into the atmosphere and what that implies for how much climate change we’re causing.

If you look at the amount of energy use by country you find that, roughly speaking, this is on average because countries differ, but they don’t differ all that widely. For every $1,000 of total production in the economy, the total energy use expressed in tons of oil equivalent tends to rise by about 0.19 tons of oil. What is 0.19 tons of oil? These are metric tons. So, a metric ton is 1,000 kilograms. So, 0.19 of a metric ton is 190 kilograms. So let me put it again this way. $1,000 of production, on average, expressed in, $2,005, let me add one more, parentheses, is associated with about 190 kilograms of oil use, or an equivalent amount of energy contained in coal or natural gas or one of the other non fossil fuel forms of energy. That gives us the scale of how much energy we use for each $1,000 of production. Now, if you look at the mix of, the energy sources in the world, mostly fossil fuels, but also some nuclear power, some wind, some solar, some some charcoal from trees some biofuel say from sugar cane converted to ethanol for automobile use as in Brazil. On average, every ton of oil equivalent energy is equivalent to about 2.4 tons of carbon dioxide emissions. In other words burn a ton equivalent of energy, and you put up more than two tons of CO2 into the atmosphere.

How much CO2? That depends on exactly which energy source you’re using. If it’s nuclear power, zero, because nuclear power is not a fossil fuel, and therefore nuclear power does not by itself create carbon dioxide emissions. If it’s coal, it’s higher than that average because coal, being almost all carbon with some impurities, when it burns, creates CO2 with little other energy created by the coal. And so coal creates the most carbon dioxide emissions per unit of energy of any fuel. Gas, and natural gas and oil emit less. So coal for a ton of coal burned, you get about four tons of carbon dioxide emitted into the air. For a ton of I should say not for a ton coal but for a, an amount of coal equal in energy to one ton of oil. That’s the right way to say it. You get about four tons of CO2 emission. For one ton of oil, you get about 3.1 tons of CO2 emission. For the amount of natural gas equivalent to a ton of oil in it’s energy content, you get about 2.4 tons of CO2. And for hydroelectric power, for solar power, for wind, zero.

632So, you can see why those energy sources are highly desirable from the point of heading off climate change. Let’s summarize again.Each $1000 of production requires a 190 kilograms, or 0.19 tons of oil equivalent of energy. And each one ton of oil equivalent on average is associated with 2.4 tons of CO2 emissions. So let’s do the arithmetic. Expressed in $2,005 used for this illustration, the world economy at 2010 was at about $68 trillion. $68 times 0.19 tons of oil equivalent per $1,000 times 2.4 tons of carbon dioxide per ton of oil equivalent energy turns out to be 31 billion tons of CO2 emission, and viola, that’s what the world released into the atmosphere in 2010 by virtue of its fossil fuel use.

So you see we can measure the size of the economy times the energy use per unit of economy, per $1,000, times the amount of CO2 released per unit of energy. And the result is a very big number, 31 billion tons of carbon dioxide released. We also put CO2 into the atmosphere as humans in other ways. We chop down trees. And when we chop down trees, the carbon that was stored in those trees is released into the atmosphere if the trees are burned or, or decay. And so carbon that was sequestered biologically is released into the atmosphere as well. That adds a few billion tons of carbon dioxide emissions in addition to those caused by fossils fuel use. Little more arithmetic. For every ton of CO2 put into the air, just a bit less than half of that stays in the air, because some of the CO2 dissolves in the ocean, some of it gets sequestered in plants and trees back on Earth. And so, of the one ton that’s put into the air, approximately 0.46 of that or 46% of what’s admitted into the air, stays in the air. And the other 54% typically is stored in what are called natural sinks, the oceans or the land.

Now, that means that if we put 31 billion tons into the air, a little over 14 billion of those tons stayed in the air. Is that a lot, 14 billion tons, for our big atmosphere? Well we can make that calculation.

We can look at the total volume of the atmosphere, how many molecules are there. How many molecules of CO2 have been put up in those tons? You have to get out your chemistry text to do that. And what you find when you do that is that for every 7.8 billion tons of carbon dioxide put into the atmosphere, the concentration of carbon dioxide in the atmosphere rises by one part per million. So that’s the translation factor. To raise the CO2 concentration in the atmosphere, which is filled with nitrogen and oxygen, and many other mole-, types of molecules. To raise the CO2 by one molecule per each million molecules of all kinds in the atmosphere, you have to put into the atmosphere 7.8 billion tons.

So this gives us now a quantitative sense of what we’re doing. If we have put 14.2 billion tons staying in the air, and 7.8 billion tons raises the carbon dioxide concentration by one part per million. Then the amount that we emitted into the atmosphere in 2010 from fossil fuel use, raised the, carbon dioxide concentration by about 1.8 parts per million or, nearly two molecules for every million in the atmosphere were now CO2 it raised in CO2 concentrations.

Is that a lot? Yes.

Is it frightening? Yes.

Let me show you why. We look again, at a graph of the concentration of CO2 in the atmosphere on the planet Earth, over hundreds of thousands of years. And the concentration of CO2 fluctuates for normal process, even putting humanity out of the story, over geologic time these levels of CO2 rise and then fall and then rise and fall as part of the long run carbon dioxide cycle. And that cycle is driven in important part by systematic changes of the earth’s orbit. And if you look at this reconstruction of the carbon dioxide concentration of the atmosphere over the last 800,000 years starting all the way to the left-hand side of the graph, the first peak you see is the carbon dioxide rose to a little bit over 250 parts per million. Then it fell to under 200 parts per million. Then around 700,000 years ago it rose again to nearly 250 parts per million and then it fell again, then it had another peak at 600,000 years ago, and so forth. So you go up and down, up and down, driven by natural changes of the Earth’s orbital cycle, but then as you move to the right that means coming closer and closer to the present on this graph. Suddenly, something really weird happens. Instead of going up down up down up down, it suddenly goes up, up, up, up, up, up, up. Shoot straight up. Just in the last 100 years of this 800,000 year graph. That’s humanity burning fossil fuel. Thank you, James Watt. Great invention. Great idea.

You made possible the world economy, but now look at the situation. CO2 soaring. How high does it go? Far higher than anything we’ve seen on this planet for 800,000 years, indeed for 3 million years. In 2013 it reached 400 parts per million. A CO2 concentration the likes of which we have not seen on the planet Earth for millions and millions of years. What the climate scientists tell us is, that this kind of change is consistent with a significant rise of temperatures on the planet. Indeed if we reach, say 450 parts per million of CO2, we are very likely to be living on a planet that on average is two degrees centigrade warmer than before the industrial revolution. Now two degrees centigrade might not sound like much, but it implies even larger increases of temperature in the higher latitudes and it implies massive changes of the Earth’s climate, of rainfall, of droughts, of floods, of sea level increase. So we’re talking about changes in CO2 concentrations that when translated into global warming, and into climate change more generally, are extremely large and extremely dangerous and happening now.

How fast are they happening? If we’re at 400 parts per million today, and that’s rising by about two parts per million each year, you can see that to reach 450 is just 25 years from now. My word. We can’t even change it at world energy system at, at that rate. So we’re on a trajectory that is very fast, and very troubling. And, add in to the fact that that’s assuming we stay where we are. Now think about tripling the world economy and tripling the amount of energy used, and if we do it using the same energy mix that we have right now, we’d be increasing CO2 not two parts per million, but five or six parts per million within a few decades. In other words, if we don’t change course we are on a path of extraordinary peril.

Where because of our fossil fuel reliance, we would be seeing mega-droughts, we would be seeing mega-floods, more extreme storms, more species extinction, more crop failures. A massive sea level rise over time, and a massive acidification of the ocean as that CO2 dissolves into the ocean, produces carbonic acid, and reduces the pH of the ocean. We have to change course, and we have to change course quickly. More quickly than the politicians are telling us, by far.

But there’s good news, let me not leave us in despair. We have powerful technologies at sharply falling prices for solar power, for wind power, for energy efficiency, for smarter systems that can economize tremendously on energy and shift us to low carbon means. We’re going to revisit some of those methods very shortly.

Growth within Planetary Boundaries II

Growth Dynamics

Now that we’ve emphasized the planetary boundaries, let’s see how hard the challenge is from the point of view of the economic growth.

We have a world now of 80 to 90 trillion dollars a year, 7.2 billion people. Approximately $12,000 per person per year on average around the planet. But the rich countries are roughly three times that average level, say $36,000 per person per year. Suppose that the poor countries, the developing world, successfully caught up with the rich world, closed the gap. That by itself would imply a three time increase of the world output, just the catching up process. Even putting aside the fact that the rich countries are still hoping to achieve some more economic growth of their own. Taking into account that in addition to the increase of total output that would come from catching up, the world population itself is also rising, from 7.2 billion people now to more than 9 billion by mid-century. To almost 11 billion at the end of the century according to the medium fertility forecast of the United Nations.


Well that means that the three time increase at our given population might amount to a four time increase taking into account the population increase as well. So imagine our situation. Our situation is one in which humanity is already causing big dislocations on the planet. But here’s a world where six-sevenths of humanity lives in developing countries. They’re looking at the high income world, they’re saying we want to live like that. In fact, they’ve deciphered a lot of the key to that, how to mobilize technology, markets, education in order to be able to have that catching up growth. And that would imply a four time increase of world output. How could it be? Could we withstand four times the human impact on the planet? Of course not. We can not even withstand what we’re doing right now. So the key, the central point of sustainable development is, that in order to reconcile economic growth and planetary boundaries we have to grow in a different way. We have to have different approaches to using energy, different approaches to transportation, different approaches to growing food in a safer and ecologically more sustainable manner.

Right now I want to look at that total increase though a little bit more carefully. A little bit more analytically. To ask, what could we expect? If we are able to solve the problem of the environmental crisis, what could catching up growth deliver in terms of aggregate output in the world in the coming decades? To do that we start with the concept of convergence.

Remember that economic convergence means that poor countries have a tendency to grow faster in output per capita, or gross domestic product per capita than do the rich countries. The reason poor countries have that chance to grow faster is not that they’re better, but because we all share similar technologies, access, knowledge and so forth. The reason they’re able to grow faster is that they have a gap to catch up. They are not yet fully using the technologies and the know-how that are already more deployed in the high income world. So a poor country has a kind of backlog that it can quickly take on of more advanced technologies to narrow the gap with the countries in the lead that we say are at the technology frontier. To understand this is, sometimes economists draw a downward sloping curve of the kind shown in this picture. You see that on the horizontal axis is a country’s level of development as a fraction of the US, the frontier country, the country at the high end of the income curve. And on the vertical axis is the growth rate of the country.


Now what’s graphed here in the solid line is the theoretical curve that says that for countries that start poor at the left hand side of the graph, their potential growth is high. And countries all the way on the right-hand side, where their income is close to the U.S. level per person, are at a lower point on that downward-sloping curve, meaning that their potential growth is lower because they have less catching-up space. And then what’s shown on this graph is the actual growth rates of a number of selected countries between the years 1990 and 2005. Lo and behold, the actual experience of countries, for instance the rapid growth of China which started quite poor, and the slow growth of Finland which started quite rich, basically fits this downward sloping line. So convergence is not only an idea, it is a practical implication of growth that we observe in, in recent years. Now, based on the experience and based on statistical analyses that have been done of this tendency towards convergence, again meaning faster growth in the poorer countries, there’s a kind of rule of thumb. The rule of thumb goes something like this. A country that is at half the income level of the country in the lead can grow about 1.4 percentage points per year faster than the leading country.

Let me give me an example. Say the United States is at $50,000 per person per year. A country at $25,000 dollars per person per year having some head room for fast growth would grow about 1.4 percentage points per year faster in GNP per capita, GDP per capita than the United States. So if the US has a growth rate per person of 1%, then the country at $25,000 would have a growth rate of 2.4% per year. Now consider a country half of that level. $12,500, so that’s one fourth of the US. Add another 1.4% per year, so that makes 2.8 percentage points per year faster than the US. So if the US is growing at 1% per annum in per person terms, a country that starts out at $12,500 per capita would be growing at 3.8% per year, 2.8 percentage points faster than the US growth rate. Well each time you cut by half the starting point of income. You raise the expected growth rate, or the average convergent growth rate by another 1.4 percentage points per year. So that a country that is 132nd say, of the United States that would be a country at about $1,562 per year just dividing 50,000 by 32. Country at 1,500, pretty poor country, maybe a country in Sub-Saharan Africa would have so much headroom that it could grow seven percentage points faster than the United States. So if the US is growing 1% per year per capita, that very poor country could be growing at 8% per capita. You get the idea. The idea is the poorer the starting point, assuming no poverty trap or other fundamental barriers to the growth of that country The headroom for rapid catching up is bigger, and one can calculate based on the statistical evidence the extent to which the growth rate will tend to be faster than the high-income country.

Now what happens over time? The poor country narrows the gap with the richer country by growing faster if it started 132nd of the income of the US, maybe some decades later it would be at a quarter of the income of the US. Then, later still, half of the income of the US. As the gap narrows, so too does the growth of that lagging country slow down. So there’s a convergence of living standards gradually over several decades, and also a convergence of growth rates. The poor country starts out very fast growing and then as it becomes richer and richer and richer, and closer and closer to the technological leader, its growth rate too therefore slows down and eventually, gradually converges with that of the technological leader. And I keep using the United States as the example of that. Let’s take a practical example of this quantitative rule. In the year 2000 the high income world had an estimated GDP per person, or gross world product per person, I can say averaging over the whole world, of about $35,000. And the developing countries had a GDP per capita on average of about 6,900 ,or let’s say $7,000 per capita. In this example if the high income countries grow at 1% per year in per capita terms, then we can calculate that given that initial gap from 35,000 down to 7,000, rounding these numbers, the poorer region should be able to grow about 3.2 percentage points per year faster than the richer region. So the convergence ideas predict that developing countries on a whole would grow at about 4.2% per year, developed countries would grow at about 1% per year. Add in a population growth rate of say, 1% for each, just being very rough. That says that the developing countries would be growing at a little over 5% per year, the developed countries at around 2% per year, because population growth is even faster in the developing countries. Maybe that would push the growth rate up closer to 6% per year compared to 2% per year for the high income countries. That’s more or less what we have been observing in recent years.

The convergence theory helps us to understand why the developing countries are achieving, enjoying faster economic growth than the high income countries. Now, if we trace this out for the next 40 years after 2010 to mid-century, and assume, that’s just an assumption, that the high income world averages 1% per year. And that the poorer regions catch up gradually with the high income region along the lines of that convergence formula that I just described. You get a kind of a graph shown here, and it’s shown with a logarithmic scale for the vertical axis. The countries start out quite far apart basically a 5-time advantage of the high income countries. But they narrow to the point where the high income countries are only 2-times, not 5-times, larger than the developing world by the middle of the century. Well what does this imply for total world production? Because remember we want to understand this to see what kind of pressures are being implied by this kind of total world growth.


To do that we now have to add back in population dynamics. And for that, we can use the United Nations forecasts of the world population. And the UN taking note of our starting point and fertility patterns, estimates that from 7.2 billion today we will reach 8 billion people sometime early in the 2020s. And we’ll reach 9 billion people somewhere around 2040. And we will exceed 10 billion people in the second half of the 21st century, and by the end of the 21st century in the medium fertility scenario of the United Nations the world will reach about 10.8, almost 11 billion people. That’s shown in this graph here. Again, it’s shown with a logarithmic scale for the vertical axis. Why? Because with that scale the slope of this curve tells us the proportionate rate of growth of the population, so that when we see the curve leveling off by the end of the century it also means that the growth rate of the world population is slowing to a low number. Today the world is growing at about 1.1%. For 7.2 billion people, 1.1% means an additional 75 million people or so added to the world population each year. By the end of the century the growth is much closer to zero to stabilizing the world population, and that’s what’s signified by this flattening of this curve in this logarithmic scale for the vertical axis.

Well we can use the population forecast combined with the convergence idea to give us a sense of what the size of the world economy might be by mid-century. If things go smoothly without disasters, and heaven knows how many disasters are possible and how many we need to fight to avoid. But assuming we don’t have the disasters and assuming that the scale of the planetary boundary challenge can be met so that this kind of convergent growth can continue, then the world economy would rise from around 82 trillion dollars in 2010, rounding a bit because these are all approximations, to around 272 trillion dollars by the middle of the century. In other words, more than a three time increase by the middle of the century. Now that’s a reasonable measure of the huge magnitude of our challenge.

We start with the world already bursting at the seams, with humanity pushing against planetary boundaries. Then we take into account the powers of economic convergence and the desires of poor countries to narrow and eventually close the income gap with the rich world. And that implies a more than threefold increase of world output by the middle of the century.

That’s why we have to think very, very hard about how our economies function because we know there is no way that on a business as usual path we could achieve sustainable development. Business as usual will burst through the planetary boundaries, will create havoc with the climate system, havoc with the water supplies, havoc with the ocean acidity, havoc with the survival of other species. In order to reconcile the growth that we want with the ecological realities, we are going to need our economies to take a fundamentally different course. That’s what we’re going to look at next.

Growth within Planetary Boundaries I

The Planetary Boundaries 

We’ve been talking about economic growth, how it started, how it diffuses, what the big problems are, how countries still trapped in poverty can spring free of the poverty trap. But the problem, we know, is more complicated than that. What if the world achieves economic growth? What if the poor countries, as they hope and rightly deserve, catch up with the high income countries? What then for the planetary boundaries? What then for an environment already under tremendous stress? Remember that sustainable development makes a key point, that economic, social and environmental systems are interlinked.

So, I want to focus now more deeply on how we might even conceive of bridging this terrible problem of global economic growth, the good that we want, the progress for poor countries, with a worsening environmental crisis. We have to understand the environmental systems and how humanity is effecting them. Then we have to look for practical approaches. How we can reduce the pressures that humanity is placing on the climate, on the oceans, on the land, or other species. So that we can reconcile these two objectives and indeed, make it possible to achieve all three of the basic goals of sustainable development. Economic growth, fairness and social inclusion and environmental sustainability.

Remember the concept of planetary boundaries or the fact that we’re living in as new geologic era, the anthropocene. Both these concepts, planetary boundaries and anthropocene, signify that humanity has become so numerous, our 7.2 billion people and rising, and so effective one could say, so productive in the capacity to mine and extract resources. To transform resources for production in industry, to consume, that we have suddenly, unprecedentedly as a species, hit these planetary risks and even dead ends if we’re not careful. The concept of planetary boundaries, I think it’s an extremely useful one, because when world leading ecologist Johan Rockström and many, many other leading ecologists got together, they asked the question in specificity. What are the major challenges coming from humanity’s impact on the physical environment? Can we identify those challenges? Can we quantify them? Can we identify what would be safe limits for human activity so that we can begin rather urgently because we’re late to this.

611To redesign our technologies and our economic growth dynamics so that we can have economic improvement while staying within the planetary boundaries. You’ll recall the picture that we looked at of the planetary boundaries around this circle. And I want to say a few words about each of these so that we can begin to look deeply at the question of how to reconcile growth and these various environmental threats. The first of the challenges and the biggest is climate change.


This is being caused by humanity’s use of particular technologies. Especially fossil fuels and the way we use land and grow animals and food that produces atmospheric change in the form of rising concentrations of a few particular gasses. Carbon dioxide is the most important of these. Nitrous oxide, methane and a few more industrial chemicals are the greenhouse gasses that have the property that they allow the sunlight in as ultraviolet radiation. But then, when the earth would re-radiate its heat to space, they trap energy in the form of the outgoing infrared radiation and thereby warm the planet. So these greenhouse gases are very particular molecules that have the property that they absorb infrared radiation.


And so when their concentration in the atmosphere increases, that warms the planet. It’s because of these greenhouse gases that life is possible in the way we know it, because that envelope of the atmosphere has made the earth warmer than say, the moon, which lacks an atmosphere. And is very, very cold as a result. But at the same time, if we perturb the greenhouse gas concentrations, raise them by raising the CO2 or the methane or the nitrous oxide in the atmosphere, then we endanger ourselves and other species. The second of the planetary boundaries is related, ocean acidification. This also comes from carbon dioxide in the atmosphere which is increasing because of human use of coal, oil, and gas. The oceans are being acidified, made more acid, by the fact that the carbon dioxide in the atmosphere dissolves in the ocean producing carbonic acid. And because of this acidity, various kinds of animal life, corals and shellfish and lobsters and very small plankton that also have these external shells made of calcium are threatened by the increasing acidity which makes it hard for the species to make their protective shells. Now, the pH of the ocean has already decreased by 0.1 unit on the pH scale from zero all the way to 14, the least acidic or basic end of the pH spectrum. A change of 0.1 in the pH oceans doesn’t seem like all that much. But this is a logarithmic scale. So, what a decline of 0.1 signifies is an increase of protons in the ocean of 10 to the 0.1. Or about 0.3, 30% increase of acidity in the ocean already with a lot more to come. If you look at this map of the ocean, you can see the changes that are already being noticed on average in different parts of the world.The oceans are not uniformly becoming more acidic. That depends on ocean dynamics. But the shading of this colored map shows that we’re already in an environment on a trajectory of dangerously rising ocean acidity. The third of these planetary boundaries is ozone depletion.

We learned a while ago accidentally, but thank God, we learned it, that certain industrial chemicals, those that were used at the time for refrigeration, mainly. Chlorofluorocarbons, or CFCs, when put into the air, would rise into the upper atmosphere, dissociate, and the chlorine in those CFCs would then cause the ozone layer in the upper atmosphere to dissociate. And a famous, horrifying finding was that there developed a big hole in the ozone over Antarctica. And when that was discovered by satellite of course people were rightly terrified. Because the ozone layer in the upper atmosphere protects us from too much ultraviolet radiation, saves us from skin cancer and many other harms. And humanity realized that this planetary boundary was already being crossed, the ozone was already being depleted unwittingly by us. This is what’s so frightening, we didn’t even know it until some brilliant atmospheric chemists unveiled the mechanisms by which these chlorofluorocarbons deranged and destroyed the ozone level.

614The next of the planetary boundaries is the heavy human caused loading of nitrogen and phosphorus. When farmers grow more food, you’ll recall that they put soil nutrients into the soil as organic fertilizers and as chemical fertilizers. Either way, incidentally, the nitrogen goes into the soil, some of it gets taken up by the crops. But a lot of it runs off the farm into the water, into the groundwater, and it collects in the rivers, and especially collects in the estuaries, the point where rivers meet the ocean. And that heavy pollution of nitrogen and phosphorus coming mainly from fertilizer use is creating a tremendous amount of ecological destruction.

We’ll have a look at that shortly. The next big challenge of planetary boundaries comes from our overuse of fresh water resources. We need fresh water every day to stay alive. Our crops need fresh water.


Of the total amount of fresh water that humanity uses, about 70% is used for agriculture, to grow our food. About 20% is for industry. And about 10% only, interesting enough, is for our household use, for hygiene and sewerage and, and and the rest. We use so much water, especially for our food production, that we are depleting very, very important sources of fresh water. For example, in the United States, in India, in China and in other parts of the world, we’re drilling for water in, in ground water aquifers, we are taking the water out, using it for irrigation. But taking the water out at a much faster rate than the water is being replenished by rainfall, and then by the water percolating back into the groundwater.

We’re depleting the groundwater. When it runs out, disaster. And that’s happening in many places in the world and will happen in many other places in the coming decades unless we are much more efficient in our water use. To grow food to feed our animals of course, humanity uses a massive amount of land. We also use land for our cities, for our parking lots, for our streets. But actually the urban areas, even though they seem to dominate, are only a few percent of the total land area on the planet. The farmland and the pastureland and the timberland that we use for forest products is a much, much larger proportion of the total land area. And humanity has been grasping over history for more and more land, more and more pasture land, more and more crop land. After all, the human population as we know has increased roughly ten times since the Industrial Revolution. That requires a lot more farmland to feed the 7.2 billion of us. The problem with that is that we share this planet with other species and as we grasp this land for our farmland, for our pasture land, for our timber land for our palm oil plantations and many many other uses.


We are literally chasing the other species away and off the planet into extinction in many cases. Our land use is having devastating consequences on biodiversity. The next category identified is aerosol loading. Small particles put up into the air because of industrial processes, or households that are burning coal into keep warm. And creating tremendous amount of air pollution, very damaging for the lungs. Claiming many, many lives per year. And with a heavy impact also on changing climate dynamics. Then there’s a very broad category of chemical pollution. Our petrol chemical industries, our steel industries, mining industries, not only demand a tremendous amount of land and water for their processing, but they add a tremendous amount of pollutants back into the environment. Many of these pollutants are persistent, they, they last in the environment, they accumulate, they can be very deadly for humans, for other species. And the range of chemical pollutants is so vast and the human and animal and plant health consequence is so large that it’s absolutely impossible to summarize, except to say that the problems are horrific in many places. China, the world champion of economic growth over the past 30 years, has also become the champion of polluted waterways of major cities, because of the extent of the heavy industrial processing.

And this all sums up to a final category of biodiversity loss. The death, the extinction of other species. We’re killing more animals and plants than we even know, than we’ve even met and catalogued scientifically, because we’re chopping down rain forest, poisoning environments, acidifying the oceans. Creating so much pollution and poisoning. That species are disappearing even before we’re able to identify and catalogue the millions of other species that share the planet with us and that we share with them. We are not stewards of global biodiversity right now. We are posing absolutely profound challenges. And when it comes to biodiversity loss, one could say that all of these planetary boundary threats, the acidification, the climate change, the land use patterns, the pollution, they’re all contributing to the loss of species, probably by the millions. It’s actually hypothesized, shocking as it may seem, that humanity is now causing the sixth great extinction wave of the planet earth. The other five, the first, for example, 440 million years ago. The next one, the second, 365 million years ago and so forth, weren’t caused by any species, weren’t caused by human beings, since we weren’t there. These were natural dynamics, whether it was, asteroid hits or whether it was the internal dynamics of the earth itself. These were natural processes. This sixth mega-extinction is not natural. It is the result of one species, that would be us, causing so much damage on the planet that we are putting millions and millions of other species at risk. And, since we depend on those other species, of course we are putting ourselves at profound risk. We are also creating a hugely unstable environment.


My colleague, professor James Hanson, recorded the extreme heat events on the planet from the 1950s till now shown in this series of maps. If you look at the map for 1955 and look at the dark red areas, you see a few places on the planet where there were heat waves in the June, July, August months of the year. And when you see those, you see that they were very particular places such as in, in Canada. Because of climate change, the number of those red splotches on the map which signify extreme heat, in that location, unusual to a massive extent for that locale, has been increasing in frequency very dramatically. You look at the map of 1955, just a couple of red regions. Have a look at the map of 1975, 20 years later, now there are a few more dark red regions of the map signifying places where extreme heat waves gripped those places. But, now jump ahead another 30 years or so to 2006 or 2007, suddenly the map is all red, it seems. The planet has been in engulfed by what was an extraordinary shock 30 years ago becoming common place now. We all know it, we’re feeling our own heat waves wherever we are. And being amazed year after year as new and very uncomfortable and often very dangerous records are set in very high temperatures gripping different parts of the planet each year. But what these maps are showing is that the frequency of these extreme events is absolutely shocking. Well, these are the planetary boundaries that have been identified. We know that we are already pushing against the limits. A

nd our question, in the coming analysis, is how can we think that that growth that we’ve been trying to decipher and promote can be reconciled with environmental sustainability and staying within these planetary boundaries when we already have so much challenge. That is our question, as we now delve more deeply into the intersection of economic growth and planetary boundaries.