Almut Gaude

“Biodiversity is like insurance against extreme weather”

Josef Settele is an agrobiologist and professor of ecology at the Martin Luther University Halle-Wittenberg. At the Helmholtz Centre for Environmental Research in Halle, he investigates how change in climate and land use affect biodiversity, and how reduced biodiversity affects ecosystems and people. Settele was a key contributor to comprehensive status reports on climate change and global biodiversity and worked with other scientists to draw up policy recommendations for the UN Biodiversity Conference in Canada.

Josef Settele
Josef Settele
Josef Settele
UFZ/ André Künzelmann

Mr. Settele, what is the state of biodiversity worldwide?

Along with two other researchers, I led the preparation of a report by the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES). All told, 500 scientists from more than 50 countries were involved in analyzing the state of animals, plants and ecosystems worldwide. The bad news is that, of an estimated eight million species on Earth, one million are threatened with extinction in the medium term – one out of every eight. Among the better known vertebrates, one out of every four species is threatened. Among amphibian species, 2.5 percent are already extinct. Besides that, we’ve observed a drastic increase in the rate of species loss in the past 50 years.

But the good news is that the million species whose loss we’ve forecast will only die out if we don’t take corrective measures in time. That means there are still things we can do to avoid this loss.

What are the main drivers of species loss?

We’ve identified five direct drivers of species loss and decreases in functioning ecosystems in the past 50 years: changes in land and ocean use, direct exploitation of ecosystems, climate change, pollution, and the spread of invasive species. Climate change is currently in third or fourth place as a cause of species loss and ecosystem degradation, with a strong upward trend. Though some species will benefit from global warming and shifts in precipitation, many more will lose out. Roughly three-quarters of species are suffering because of rapid warming. The other quarter could benefit.

What is the exact connection between the climate crisis and biodiversity?

If systems are to function well, climate and biodiversity have to be considered in concert. If we have a balanced climate, that gives us more species that can keep our ecosystem working. And if we have many species, that gives us more options for keeping carbon sequestered. So biodiversity helps to ensure that the carbon stored in soils and plants over the decades and centuries will stay there and not be released.

Can you name a specific example?

There’s one right in my neighborhood: the Harz region with its many spruce trees and bark beetles. The bark beetle is a species that thrives in warm weather and is spreading here in Germany as temperatures rise. By itself that wouldn’t be a problem if we had a wide variety of tree species in our forests, because bark beetles only attack weakened trees. But spruces, in contrast to many other local species, are especially vulnerable to rising temperatures and drought.

If one species in a healthy mixed forest is lost due to higher temperatures and bark beetle infestation, there will still be other more resistant species and the forest will remain intact. Forests with a greater variety of tree species are also more resilient against changes in climate, so they can act as long-term carbon stores.

The problem, though, is that we have a lot of spruce trees in our forests. Some are even exclusively spruce. That’s due to human activity in places like the Harz. If global warming weakens the predominant species – spruce in this case – it becomes easy prey for bark beetles and the entire forest can be lost in a short time. Then a large amount of the carbon stored in the forest is released, harming the climate.

We have to understand that preserving and restoring biodiversity is insurance against damage and extreme weather. And you know how it is with insurance: It’s not a luxury, it’s a good and necessary thing. People take out insurance for emergencies, in the hope that they won’t need it in the end.

Your specialty is land use, for example by farming and forestry. Are there examples of land use that ensures a high level of biodiversity and is also good for the climate?

A prime example involves traditional land use systems where a balance between people and nature has been established over a long period. For example, here in Germany that would be permanent grassland areas like the juniper heaths in the Swabian and Franconian Jura, or the mountain pastures in the Allgäu region. These landscapes have been used for centuries as pastures for cattle or sheep. They’re true biodiversity hotspots, home to rare species of butterflies and bees. At the same time, grassland that has been worked extensively for long periods has a very high capacity for carbon storage. That’s not as obvious for pastures and meadows as it is for forests, but the dense and extensive root networks of grasslands can also absorb a lot of carbon. Here too, the greater the variety of herbs and grasses a grassland has, the greater the buffering effect when one or more species is lost because of rising temperatures. 

The UN Biodiversity Conference will take place in December 2022 in Montreal. In your opinion, what is the most important thing that has to be done to help both biodiversity and the climate?

There are three things. First, wetlands and forests, and also old cultural landscapes, must be protected and restored – in the places where they were in the past. That’s because new trees grow best where trees have grown in the past, not on grasslands that are valuable for the climate. Second, we have to set our sights on our supply chains and consumer habits. A lot of what we consume is produced abroad and damages the environment there. It can’t be that our consumer demand causes huge swathes of valuable forest to be cleared in Indonesia or South America for the production of palm oil or to grow soy as feed for our livestock.

We need more quality instead of quantity, meaning we can’t continue with our current consumption of meat. The animals need far too much energy, especially pigs and cattle. We have to change that. We have to cut back on factory farming and promote extensive land use – in other words, preserve and expand the careful use of grasslands for livestock. And third, the countries of the Global South need financial assistance so that they can preserve the biodiversity of their natural landscapes, the variety of their livestock and crops, and their local small-scale and correspondingly diversified farming methods. An initial step in this regard is the fund that was just adopted at the end of November by COP 27 to compensate the world’s poorer countries for climate-related damages. Something similar, but more forward looking, would be good for biodiversity.

Are there also climate protection measures that are harmful for biodiversity?

Some alternative green energy sources are one example. Wind power is a problem for bird conservation, of course, though I find the heated debates about it somewhat overblown. What we agree on at both the Intergovernmental Panel on Climate Change (IPCC) and IPBES is that monocultures are not appropriate for bioenergy. Valuable land for food production and biodiversity is being lost to huge cornfields that are only used to produce bioenergy. Using wood or corn for bioenergy in such a way is complete nonsense. That’s the consensus of a very large majority of scientists and also numerous government representatives who shared this view at international negotiations.

Thank you for the interview, Professor Settele.

Share article