Ecosystems provide vital services for human well being, provisioning and regulation among them. Biodiversity, the variation of life within species, across species, and across ecosystems.
Determines to an important extent, how well ecosystems perform. And therefore, how well they provide vital services for humanity. There was a long standing hunch that a greater degree of biodiversity. More genetic variation within species a richer web of species in a food chain or in a given ecosystem, would raise the performance of ecosystems. And over the last 20 years, ecologists have been making valiant efforts to understand the linkage of biodiversity to ecosystem functioning. Their conclusion is a very strong one. And that is that biodiversity, biological diversity, raises the performance of ecosystems in valuable ways. And when biodiversity is under threat, at any level of organization, less genetic variation within a species, less variation of the range of species, less favorable interaction across ecosystems. When biodiversity is a threat, ecosystem functions are degraded.
Let me give just a few examples of what has been found as reported recently in some overviews of this linkage, from biodiversity to ecosystem functions. Consider provisioning, for example. The way that ecosystems provide food or fiber for human needs. One thing that’s found is that crop yields are higher in farm systems that have a higher biodiversity. This is a very big deal, because a lot of the industrial food production is monoculture. One kind of crop grown massively on a farm, rather than a high biodiverse farming system. And even within, that one crop, whether it’s rice, or wheat, or maize or, some other crop, it’s one seed variety perhaps, industrially manufactured.
And so what’s happening is that the biodiversity of our farm systems is shrinking. And one of the findings is that this is making our farm systems less productive. Yields actually go down. And maybe farmers don’t know this individually, or they haven’t had the experience, or they’ve become part of an industrial food chain that has discouraged a highly biodiverse farm system, but the results are farms in threat. And farms that are monoculture are also far more vulnerable to the invasion of pests and pathogens. One of the things that biodiversity does is protect an ecosystem from an invasion. In invasive species like a weed variety, or in invasion of a pest that attacks a certain kind of plant. If there are multiple kinds of plants in the ecosystem, maybe there’s some loss, but the parasite or the pest is controlled. But if there’s one monocle through it can tear through the entire area without limit essentially. So the resistance to invasions, to parasites, to pests is also reduced. Another finding quite similar is in marine ecosystems.
If there is a reduction of biodiversity of the fish species. And that’s happening all over the world as fishermen clear a particular fisheries area of the most favorite species, or particular easy to catch species, or the fewer numbers at the higher trophic levels of the ecosystem, meaning the kinds of fish that it, that eat other fish, that are piscivorous that are fish eating fish and higher up on the food chain. In other words, the phenomenon has now been verified by ecologists across many different kinds of ecosystems and many different kinds of reductions of biodiversity. also, when it comes to implications for climate regulation, reducing ecosystem performance by lo, a loss of biodiversity also can reduce storage of carbon in cycles, or in plant life.And therefore, essentially, releasing carbon dioxide into the atmosphere because there’s less biological sequestration of the carbon within the ecosystem. So the regulatory functions of ecosystems in climate as well, are degraded when biodiversity is lost. Now, that’s all pretty bad news, and the reason it’s bad news is that in ecosystem after ecosystem, biodiversity is at massive threat. It’s already being reduced, degraded, hugely threatened. Why? For so many reasons that it’s going to be extraordinarily difficult to bring under control. A summary perhaps that’s useful is to look at a map of the world that was prepared by my colleagues at the Earth Institute a number of years ago, called the Human Footprint Map. What my colleagues did was to take a number of indicators. For example, population density, land use change, infrastructure coverage railroads, roads, other human changes. Aggregate them, weight them in an index, and then for each small part of the world, the kilometer by kilometer ask, how big is the human influence, the human footprint in this part of the world. And they came up with a map that looks like this. The darker the red, the stronger is the human footprint. If an area is all green, that’s a part of the world very little touched by human influence.
Well, what you see in this map is the sweep of humanity. Humanity is basically everywhere where it’s habitable. And so you look at the United States there’s no dark green area essentially in the continental United States. The eastern half of the U.S. is much darker red than the western half because it’s much more densely settled. In part because it’s it is more humid, there is more food production and the western part of the United States by and large is arid and more mountainous, with much less population density. But even there, the human activity, land use change, pasture land, farm land, urban settlements, roads, rail, are pervasive. So where are the dark green areas? well, in Africa, the desert, the Sahara desert. Yes, very, very low human impact, but very, very few people living in the Sahara. For the boreal regions of the Eurasian landmass. Up in the tundra. where there are still forests and very little population because it’s frozen much of the year or year round. And there’s not agriculture in these very high latitudes. And so there’s relatively low human impact. But look at India. Look at China other than the Tibetan Plateau at 20,000 feet or more above sea level. Look at South America aside from still parts of the Amazon rainforest.
What you see is the pervasive human footprint. Humanity is everywhere. And just like the underlying index that is the basis of this map, humanity is everywhere in many, many different ways. It’s there in infrastructure, it’s in farming. It’s in changes to basic chemical cycling, as we’ve talked about so much in water use, or nitrogen cycling, or phosphorus cycling, as a result of agricultural activities. Now, a related idea was led by a great ecologist, Peter Vitousek. now, more than 15 years ago, when he and his colleagues asked the question about human domination of the ecosystems. How much are we taking in that provisioning. We need food. We need pasture land. We need areas to to, to put our asphalt down for our cities and our roads, and our parking lots. How much of the global ecosystems is humanity appropriating? What is the human domination? Their conceptual framework for that is shown here in this complicated flow chart. They start at the top with human population both its size and the resource use. Then, the human enterprises, they called it, what humanity does in agriculture and industry and recreation in international trade. Then they talked about the several ways that human activity appropriates or dominates ecosystems. Land transformation, for example, farming or land clearing for pasture land and for use of forests could be the change of the cycling of key nutrients and chemicals and the ecosystem as we talked about like nitrogen or the water cycle or the carbon cycle with its enormous effects on climate. Or changes directly in the biosphere. As we harvest crops, as we hunt species, as we fish for fish. Or as we rearrange the biogeography of species by saying, why don’t we take that species from Australia and put it here, without having a deep understanding of what happens when one species invades another ecosystem where its predator or control mechanisms might not apply. And all of this, if you go down the flow chart, changes the climate system, for example, through the greenhouse gases of carbon dioxide, methane, and nitrous oxide. And leads to a loss of biological diversity, which is our main focus right now. So what Professor Vitousek and his colleagues did was to try to assess how big is the human domination of ecosystems by several fascinating metrics. How much land has humanity transformed? How much have we changed the carbon cycle? What have we done to water use and so forth? Their conclusion revealed the massive extent of human impacts across all of these dimensions. Land area, 40, 50 percent of the total net primary production through photosynthesis on the planet is for us. That’s a pretty voracious species. We are grabbing and have grabbed land area. Whether it’s the pastures, the forests, the arable land. And said okay to the other species, we’ll take that, thank you. That will be our pasture, that will be our farmland, and the extent of the human reach on land transformation is perhaps half of the total net primary productivity on the planet. CO2, we know we’ve changed the carbon cycle fundamentally, and already raised the level of carbon dioxide in the atmosphere from 280 parts per million, pre-industrial revolution, to 400 parts per million and rising. Now, water use. Tens of thousands of dams put on the world’s rivers. Massive taking of groundwater for irrigation especially. Harvesting the the flow that comes from glacier melt. And that very dangerously for us is going to come to an end as those glaciers retreat and then finally disappear under the force of global warming. Water use in crisis in many, many parts of the world because we have appropriated so much. Of the the, the available fresh water cycling. Nitrogen, we know we have come to dominate the nitrogen cycle. Turning N2 in the atmosphere into so called reactive nitrogen like ammonia or nitrates and nitrates that can be taken up by living organisms, is, both a natural process as we’ve discussed but also an industrial process, the Haber-Bosch process. That famous process that enabled humanity to grow so much more food that it made it possible for the population of the planet, to rise from not quite two billion people at the start of the twentieth century, to six billion people by the end, and now 7.2 billion people. We have threatened species so much that we realize that we need to classify and measure the species, that are endangered. We need to understand the extent of these dangers. and, the International Union for the Conversation of Nature, the IUCN, is the global score keeper of endangered species. It’s extremely important to understand what they’re measuring, and how they’re measuring it. And that is shown first on this diagram which helps us to understand the classification system used by the IUCN. Now the first thing to say is that there are an unknown number of total species on the planet and theories vary roughly between ten million species of all kinds. Plants, animals, microbial life. To possibly up to a 100 million species. We’ve not classified, large proportions of those species. So IUCN, still is in the process of classification, as is the world scientific community. Of those that are classified, then there are categorizations of species that are not threatened by human activity, they’re so in, in so many places and in such large numbers that humanity does not pose threats. To those that have already been driven to extinction. And you can see here the classification that are of, of the various gradations of threat. Species that are extinct because of human activity. Species that are extinct in the wild but perhaps still live in small numbers in captivity. Critically endangered species, endangered species, vulnerable species, near threatened species, and those of least concern. So, the IUCN keeps its so-called Red List which gives the numbers of species in these very threatened categories. And you’re looking at the tables for critically endangered, endangered, and vulnerable species. And when one looks at the numbers, it’s of course, very, very frightening because even in a very short period of time, the numbers classified as critically endangered, for example are soaring. Partly this is through new classifications and adding species that have not been classified before. But it’s also very much that human activity is driving species to the state of being critically endangered and to extinction. The IUCN Red List is invaluable and of course, it is profoundly troubling. We know that major classifications of animals and plants are being pushed to the extreme, the critical danger levels and some to extinction. And just to mention, a few that are most dramatic amphibious species the world over are declining hugely in numbers. And this is taking place ac, across the range of amphibians and it’s taking place all over the world. Recent studies for the United States have shown an enormous drop-off. And one of the frightening things for the loss of amphibians in the United States is those that had the highest proportionate drop-off in frequency of sightings are the ones that were classified by IUCN as the most endangered. And so the declines of amphibious species are not taking place in the most abundant and safest but in the most endangered. Another major collapse, of of species are pollinator species which are so vital for our plants and our fruits and our food provisioning. The honey bee, in the United States, has been experiencing a dramatic, troubling and still poorly understood decline in numbers. And in some cases, a collapse of bee colonies that has come to be called the colony collapse disorder. And it is so striking with the fall of numbers. But even more striking perhaps, that we don’t quite understand why, where, what’s happening to this radical die off of bees across the United States. There are many potential culprits, Could be a parasite, a parasitic mite has been implicated, but then again multiple viruses have been implicated. Bacterial diseases. A drop of, nutrition, of, the honey bees, coming from changes of landscape and crop varieties. And many, many scientists think that it’s the increased use of pesticides that is a major cause of this. Another absolutely shocking, and dramatic, and troubling loss of species abundance and threat of extinction are the great apes. Our closest relatives on earth where humanity shares the genetic code and the evolutionary history just as close as can be. 95% or more of the genetic code shared with great apes, with the gorillas, chimpanzees, orangutans bonobos and the dramatic decline of numbers of these great apes and of their habitat in the last 25 years is absolutely shocking. I had the occasion recently to visit one group of eastern mountain gorillas in Rwanda in Volcano National Park, which is doing a valiant effort to preserve the habitat of the mountain gorillas. It’s of course an incredible experience to be together with the gorilla group and to see them in the wild. And it was absolutely rather shocking to see how fragile is the remaining habitat for these endangered gorilla groups. Because the farm land, under tremendous population pressure is pushing right up against the the cloud forests, the bamboo forests, that are the habitat of the mountain gorillas. There is a stone wall which separates the farm land from the the bamboo forest. One doesn’t go far inside the bamboo forest to meet with the groups of the gorillas. You see how close humanity and the gorillas are living together and by the way, that means that humanity can pass pathogens, diseases, human diseases to gorillas. We share so much of our biology, of our genetics of our immune systems, that the diseases easily flow in both directions and disease itself can be transmitted to these gorilla groups. Well, it was breathtaking to be together with the mountain gorilla family and and a mountain group in the wild. But it was absolutely shocking to see how humanity has pressed against the remaining habitat for this species. The, the one of the closest relatives that we have and how fragile is that distance now that that is their margin of survival on the planet. These pressures are coming in all directions. They are causing huge risks to biodiversity. The risks to biodiversity are causing huge losses of ecosystem functions, and we have to understand now what we can do about it.