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World Biodiversity Forum 2024

“Climate change and biodiversity are closely connected”

The third World Biodiversity Forum (WBF), organized by UZH, is taking place in Davos this week. In this interview, UZH earth system scientists Maria J. Santos and Gabriela Schaepman-Strub explain how biodiversity and climate change influence each other and what needs to be done to overcome the climate and biodiversity crisis.
Interview Thomas Gull / Translation Mark Rabinowitz
USA, Colorado - A black-tailed prairie dog guards his fellow species in the wasteland next to the highway to Boulder. (Picture: Ethan Welty)

This week, the WBF will be discussing what is needed for a sustainable future and how science can contribute to this. The two UZH professors Maria J. Santos and Gabriela Schaepman-Strub are on the forum’s scientific advisory board.

Maria J. Santos, Gabriela Schaempan-Strub: The 2015 Paris Climate Agreement set a goal of limiting global warming to 1.5 degrees Celsius, or at the most to no more than 2°C, above pre-industrial levels. Where do we stand today? Is that goal still achievable?

Maria J. Santos: If all manner of measures were to be embraced immediately, if emissions were halted, and if all proposed ways of capturing and sequestering carbon were financed right away and implemented on a large scale, then we could stay below the 1.5°C benchmark. But since it takes time to put those solutions into action, the most likely and best-case scenario is staying below 2°C. Yet even this requires taking very swift action within the next few years. Otherwise, it is very improbable that we will be able to stay within the 2°C limit.

Does this mean that tipping points resulting in fundamental and irreversible changes in the Earth’s climate will be reached?

Gabriela Schaepman-Strub: We are well on the way to two degrees of warming. The aims of the climate accords are tied to specific elements of the Earth system for which there is a likelihood of tipping if the defined temperatures are exceeded. We know that the Earth today has already reached a warming tipping point at which it has become probable that tropical coral reefs will die off. Moreover, we’re talking about a global temperature increase of 1.5°C to 2°C, but local warming can far exceed that. Certain regions thus are already very severely affected even if we stay below 2°C. In the Arctic, where I conduct research, warming is three to four times greater.

What will happen if such a tipping point is reached? Will the impacts be catastrophic? Or will the system find a new equilibrium that we can live with?

Santos: What does it mean to live with a new equilibrium? Take the Amazon, for example. The resilience of forests in the Amazon River region has diminished since the 2000s. If 20% to 25% of the woodlands there get deforested, the Amazon basin will probably turn into grassland. That will have an impact on both the local and the global climate because the rainfall currently produced by the Amazon forest and its carbon fluxes affect temperatures around the world. However, it’s not that easy to predict because new estimates suggest that the effects of disruptions such as deforestation, fires and droughts may have already accelerated this process in the Amazon region. Furthermore, triggering this tipping effect in the Amazon region or reaching other tipping points in the Earth system such as in the Arctic has cascading effects in other regions. This raises the question of whether we can live with that. The planet will survive. Some elements of the biosphere will survive. But many areas of the world could become uninhabitable for many species, including humans – hence the urgency.

Schaepman-Strub: If the system tips into a different state, the new base state will be pretty stable and will be hard or even impossible to reverse. Take desertification – if an area has been desertified, feedback loops stabilize that state. Once vegetation is lost, there is no longer evaporation, so the cooling effect also vanishes and rain ceases to fall. Moreover, bare ground devoid of vegetation is susceptible to erosion, which depletes nutrients in the soil. That’s why it is very difficult to repopulate plants once the original vegetation has been lost.


If we want to halt climate warming, we need to concern ourselves also with biodiversity and land-surface use changes.

Gabriela Schaepman-Strub
Earth system scientist

Will we lose parts of our planet as a habitat for humans?

Santos: That’s the idea of planetary boundaries. They define secure habitats for humanity. If we want to preserve climatic conditions that humans can withstand physiologically and in which they can live with a certain degree of well-being, then we have to respect those planetary boundaries.

Schaepman-Strub: If a pivotal climatic element tips, we expect that vital processes of the global climate system will be affected. That’s why it’s so important to have a whole-system perspective. If the Amazon tips or if the boreal permafrost abruptly thaws, then we here in Switzerland will also experience effects that go beyond just two degrees of warming and a little nicer and drier summer weather. The new global tipping points are closely connected with the entire global system. If they tip, they will destabilize the entire global climate.

Can you give an example?

Schaepman-Strub: If the temperature gradient between the North Pole and more southern latitudes is no longer as large as before, there will be more breakouts of cold air masses from the Arctic. They, for example, will then blanket agricultural land in the subtropics of Southeast Asia with frost, harming harvests there. It wouldn’t enter anyone’s mind that this is due to a destabilization of the entire global climate system, but in fact it is precisely attributable to that.

For a while, people perceived global warming and loss of biodiversity as merely abstract warnings from scientists. Today, in a sense, we are finding out firsthand what climate change and species extinction really mean. What has changed?

Santos: The very first predictions about climate change are around 70 years old now. Back then, the effects of climate change were barely noticeable. As predicted, though, in the meantime a tremendous amount of carbon dioxide has accumulated in the atmosphere. As a result, the global climate is warming, and the climate system is behaving more chaotically. As warming increases, so does the incidence of climate extremes. Those extremes – droughts, floods and wildfires, for example – are generally much more palpable and put a lot of stress on ecosystems. There is a debate underway in the scientific community about whether the very warm year 2023 is just a part of the variability or is actually the new climate that we have to live with.

Why did this development take the scientific community by surprise?

Schaepman-Strub: Climate models do not take many of the feedback loops into account or factor them in with inadequate precision. That’s why there are effects that are much more strongly impacted by climate warming than we are currently modeling.

Santos: One example is changes in land use brought about, for instance, by the expansion of cropland or by deforestation. Today we don’t have any good models that reflect those changes because they differ greatly geographically and are hard to capture. That’s because changes in land use are brought about by many different biophysical, economic and political processes. We need better and more thoroughly integrated models. That’s exactly what we’re working on right now.

Unexpected changes are also occurring in the Arctic region, caused in part by large tundra wildfires. How does that affect the Earth’s climate?

Schaepman-Strub: Those wildfires are especially alarming because they trigger very problematic feedback loops. When wildfires burn, the Earth’s surface turns black and absorbs much more solar radiation. The resulting intensification of warming thaws the permafrost, and the ground releases carbon dioxide and methane into the atmosphere. Current climate models do not factor in those methane emissions. Permafrost soils contain twice the amount of carbon as is currently present in the atmosphere.


We have to change our way of life and how we use natural resources and need to think about what kind of world we want and what are fair compromises to attain it.

Maria J. Santos
Earth system scientist

You have studied and researched phenomena and changes like the ones just described as part of the University Research Priority Program (URPP) Global Change and Biodiversity. The URPP ends this year. Now you are working together with Owen Petchey on a new vision that aims to take the entire biosphere – all parts of the Earth that are inhabited by living organisms – into account. What’s your objective?

Schaepman-Strub: Biodiversity and climate are very closely connected. Changes in biodiversity affect humans and animals, but also have an impact on the Earth’s climate. So, if we want to halt climate warming, we also need to concern ourselves with biodiversity and land-surface use changes. To us as researchers, this means that if we want to come up with solutions, we really have to research these problems conjointly. We intend to concentrate even harder on that in the future to gain a truly complete understanding of the macrocosm of processes at work in the biosphere.

Santos: What must we do to have a well-functioning biosphere? That’s the next question we want to answer. To do that, we have to think beyond disciplinary boundaries and work together as a team. At the center of it all is the biosphere and how it interacts with other Earth system processes, how living organisms affect each other, and how species and other dimensions of biodiversity such as genetics or the functioning of ecosystems contribute to the stability of the biosphere. We want to integrate the entire intricately interconnected complex into the new vision.

Schaepman-Strub: To do that, we need not just know-how in natural sciences, but also in ethics and sustainable finance. We need to incorporate different intellectual approaches to take our understanding to the next level, which is imperative today.

I’d like to go back to a more general question. What needs to be done to preserve the Earth system’s current fragile equilibrium?

Schaepman-Strub: Would you like a political or a scientific answer?

Both, ideally.

Schaepman-Strub: I think that we need to reconsider the paradigms of today’s economic system. If it continues to operate on the doctrine of economic growth, it will be very difficult to stay within planetary boundaries. But I’m unsure about whether and how we can bring about a real change. We already know an awful lot. We can point out which solutions are sustainable and which ones are not. But in order to implement them, we have to win over the people who call the shots in politics and business. For many of them, changes of this kind would entail near-term costs. Persuading those influential stakeholders is arguably the biggest challenge.

Santos: We need transformative change because our system – the human-nature system – is not doing what it must do. We definitely need to rethink how we produce and consume goods and must challenge the paradigm of continual growth. We have to change our way of life and how we use natural resources, and we need to think about what kind of world we want and what are fair compromises to attain it. If we’re talking about truly transformative change, we have to think about the entire world and ask ourselves: Sustainability for whom? And who gets to decide this?

Schaepman-Strub: An important point is that the business world at present does not incur any external costs for its use of natural resources – costs stemming from pollution of the environment or the loss of woodlands’ cooling effect on the climate due to deforestation. Those, in fact, are enormous environmental costs that get externalized to society, and natural resources are finite. Those environmental costs ought to be factored into the prices of goods.

The ultimate problem is bound to be that nobody wants pay the price for the changes needed.

Schaepman-Strub: We have to think about the meaning of growth. Growth currently means that businesses generate more and more revenue and pay out more and more profits to shareholders. But maybe that’s not the kind of growth we want and is no longer the kind of growth that we can afford on our planet. Growth ideally could mean a better quality of life for the greatest possible number of people and an improvement in biodiversity instead of higher profits for the few.


Maria J. Santos is a professor of Earth system science. She conducts research on linked social-ecological systems, with a special emphasis on tropical ecosystems that are home to an above-average share of global biodiversity and are greatly affected by climate change, economic development and population growth.

Gabriela Schaepman-Strub is a professor of Earth system science. She conducts research into how climate change and other global drivers are altering Arctic biodiversity and investigates what feedback effects those changes have on the thawing of permafrost, on the climate and on people in the Arctic.

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