No. 111/2020

FOCUS 22 HUMBOLDT KOSMOS 111/2020 and the production of plant biomass, which are fundamental for supporting the livelihood of more than 1 billion people globally. Until a few years ago, nobody imagined that bio­ diversity could play such an important role in global drylands. Also, in the last 30 or 40 years, we have seen a real greening of dry- lands worldwide. This indicates that a lot of additional carbon bonding is taking place. What has caused the greening? The increase in the proportion of carbon in the atmosphere has made plants more efficient in taking up water and thus stimulated their photosynthetic capacity. So, they have been able to grow more. However, in some regions this effect has already reached its peak, espe- cially as climate change is responsible for increased warming and decreasing levels of rainfall. UNTIL A FEW YEARS AGO, NOBODY KNEW THAT THE SOIL IN DRY REGIONS STORES SO MUCH CARBON.” How much carbon dioxide does the soil emit? Professor Maestre meas- uring soil CO 2 efflux at an experimental site near Alicante, Spain. But will the additional growth not be able to compensate for the lack of rain caused by climate change? We can’t make any generally valid statements about future rainfall levels across the world yet. Some areas may receive more rainfall, but others will experience extended droughts and receive less rainfall. But we are confident that global warming is increasing evaporation and associated water losses, and this effect may not be compensated for by the positive effects on plant growth promoted by having more CO 2 in the atmosphere. This is aggravated by the fact that the dry areas in some regions of the world are in a bad state. Why is that? One reason is that the trees and shrubs have been cut down in many dryland areas, which often have also been overgrazed. Drylands host more than 2 billion people, 90 percent of whom live in developing countries where they rely on what the environment has to offer – from their livestock who graze on existing vegetation to whatever they can cultivate. What would have to change? We could do a lot by managing grazing. We are getting very revealing data on how live- stock grazing affects dryland ecosystems and how much grazing a dryland ecosystem can support before it becomes irreversibly degraded. Measures to help to conserve bio- diversity are also key, as our data demonstrate the importance of plant and soil biodiversity in improving plant productivity, preventing soil erosion and delaying the onset of deser- tification. When people are struggling to survive, envi- ronmental protection is not a priority. How are your suggestions received? In developing countries, we often have a harder job explaining to people that they must change certain behaviours, not just for envi- ronmental reasons but because otherwise they are endangering their own livelihoods. What kind of contribution are African researchers making here? They carry out a large share of the field stud- ies on this continent. In our network we have “