When we’re exploring sustainable development in the Anthropocene in the era when we no longer can exclude undermining the way the entire Earth system operates, we must understand and explore what resilience means across different scales.
So we’ve been exploring the resilience of systems, the ability of a household or an economy or a rainforest to withstand different disturbances without shifting into a different structure or function, for example, a rainforest tipping over into a savannah. We must explore what is the risk of pushing the entire Earth system outside of its stable state. We call this Earth resilience.
Earth resilience is entirely dependent on the different components of the Earth system operating together and either through what we call negative feedbacks, meaning processes that dampen change, or through positive feedbacks, where processes actually accelerate change, and applying these interactions regulate the ability of the Earth system to remain either in a Holocene-like state or propel itself outside of that state.
So in exploring Earth resilience we must also understand what we call cross-scale interactions, how for example a carbon sink or a methane sink in a local forest, or a wetland, or a savannah, interacts with the atmosphere or the polar regions, so from a local, to a regional, to a global scale. That is different to Teleconnections, which is when one system changes in one place of the world and has domino effects on other systems.
For example when a forest system that feeds back moisture and creates rainfall affects the monsoon system several continents further away. These are complex notions but must be understood in the Anthropocene. And in this lecture we’ll explore a bit further what we need to understand when we define Earth resilience. Now it takes us back to the absolute starting point when defining our desired future, which is going back to the ice core data which defines our desired state, namely the Holocene. So this is again the hundred thousand years of change in the world showing that the last ten thousand years in the red circle here is an unprecedented stable state of the planet. In fact we can call this the Eden’s Garden of human development, the stable state within which we want to remain.
The reason why referring to this state when exploring Earth resilience is that the Holocene is a state that we understand very well. We know the carbon cycle, the nitrogen cycle, the phosphorus cycle, and the limits within which essentially all the key parameters that regulate the stability of the Earth system have been operating over the past 10 000 years, illustrated for example in this extraordinary set of data showing concentrations of carbon dioxide and methane over the past 400 000 years.
And if you look very carefully you’ll see the very stable and narrow range within which these gases operate over the past Holocene, and the blue arrow showing how we are moving away from this very stable state.
This Is very helpful, it actually helps us define a safe operating space for human development because we understand fairly well how, and what are the conditions, within which the Earth system can operate in the Holocene. Now the excitement about this comes across I think in a very pedagogic way in the following exploration of what role does the biosphere, the ecosystems of the world, play in terms of trying or attempting to maintain a Holocene-like state? And let me just run through this example to you in quite detail.
So we are emitting greenhouse gases and have been doing so since the Industrial Revolution in the end of the 18th century. We’ve emitted an estimated 365 billion tons of carbon from industrial emissions, and another 180 billion tons of carbon from land use change.
That together ends up in an enormous 545 billion tons of carbon emitted cumulatively since the Industrial Revolution. This is relevant because carbon remains in the atmosphere for over 1000 years. So what we did 200 years back is still warming the planet.
The big question is temperature has risen with almost 1° Celsius since the Industrial Revolution. Is it all of these 545 billion tons of carbon that now reside in the atmosphere causing 1° Celsius warming? The answer is no, because the astonishing reality is that over half, roughly 55%, of these emissions are actually absorbed by the living biosphere, 155 billion tons in the oceans, and another 150 billion tons are estimated to have been taken up by terrestrial ecosystems.
This is the most profound proof that the Earth system, through its biogeophysical processes, is applying Earth resilience in practice, meaning that the Earth system is applying these processes to try to remain in its current stable state, the Holocene, by dampening the impacts of our disturbance, emitting of carbon dioxide in this case.
And these carbon sinks are tremendous. And the net remaining amount of carbon in the atmosphere is only 240 gigatons of carbon which has contributed to the temperature rise so far.
Same story goes for heat, for example. 95% of the heat caused by global warming is stored deep in the oceans. These are all processes that try to dampen and maintain the self-regulating biogeophysical processes in the Earth system in the Holocene-type state. Now it goes beyond just understanding the big climate system.
There are critical functions that all the biomes play in regulating Earth resilience. So the polar regions, for example, are permanent white surface areas that reflect roughly 90% of incoming heat from the Sun, reflecting it back to space. These polar regions are massive air conditioning, cooling systems for planet Earth, thanks to their permanent white surface.
These are negative feedbacks. They’re actually cooling the planet. When ice melts and changes color to a liquid surface, just that color change means that instead of reflecting back heat and functioning as a cooler polar regions can transform themselves into becoming net absorbers of heat, meaning becoming positive feedback triggers, self-generating heat.
Same with rainforests currently being huge carbon sinks, regulating moisture feedback and rainfall patterns across the world, being residuals or residing massive hosts for biodiversity, and also generating oxygen; marine systems functioning and heat conveyers, carbon sinks, and banks of genetic diversity; the world’s temperate organic systems being sinks and huge stores of methane; the temperate forests also being major carbon sinks and regulating rainfall patterns and generating oxygen across the world; and finally savannah systems that are playing also a role as moisture feedback, and regulating carbon and rainfall patterns; altogether systems that define Earth resilience.
And the key insight here is the recognition that in the past we’ve been very preoccupied of managing ecosystems at the local scale. This has been important for local livelihoods and local opportunities for good living conditions. Now we must connect the local to the biome scale, and the biome to the planetary scale, and recognize that we have to become stewards of all these systems collectively because they determine the ability for any scale, from household to business to nation, to develop in the future.