How vulnerable are forests to extreme events?

Earth system scientist Dr. Ana Bastos will join the Institute of Earth System Science and Remote Sensing at Leipzig University from 1 May 2024. In her research, the future Professor of Land-Atmosphere Interactions will combine atmospheric research, ecology and biogeochemistry. Among other things, she investigates the interactions between land and atmosphere, the effects of climate extremes on ecosystem dynamics and disturbances. In this interview, she provides insights into her current research and talks about her plans for her time in Leipzig.

With the ERC Starting Grant "Forest Vulnerability to Compound Extremes and Disturbances in a Changing Climate" (ForExD), a highly remunerated five-year grant from the European Research Council (ERC), you are investigating how vulnerable forests are to extreme events and disturbances, in connection with climate change. The damage to forests in central Germany has been highly visible. What specifically are you investigating here and what have you already discovered?

The aim of the ForExD project is to better understand how weather and climate extremes are linked to forest disturbances such as fires, insect outbreaks or drought-related tree mortality. In the last decade or two, we have seen many surprising disturbance events related to weather extremes, for example mega fires from Australia to Alaska or the widespread tree mortality in Central Europe after the summer drought in 2018. I am interested in three questions: How has climate change contributed to these events, why are some forests more vulnerable to extremes than others, and what does this mean for climate change mitigation? In the case of tree mortality in central Europe and therefore also central Germany, for example, we have shown that this was not only due to the drought of 2018, but the cumulative effect of three consecutive hot and dry summers from 2018 to 2020, which have reinforced each other’s impacts. In some countries, such as the Czech Republic, these effects have led to forests releasing carbon into the atmosphere, instead of absorbing it. This is worrying, as many measures to mitigate climate change depend heavily on forests.

In your opinion, what role do climate extremes play in changing the dynamics of the carbon cycle and how can we better prepare for them?

Currently, forests absorb almost 25 per cent of human-made CO2 emissions. But we also see that weather and climate extremes can lead to large carbon losses, which in some cases are not immediately compensated by subsequent regeneration. In light of recent extreme events, there are strong indications that the storage of further carbon in forests may soon be jeopardised by increasing disturbance events. However, we cannot yet model these complex interactions, which means that there may be a feedback to climate change that we do not yet fully capture in our projections.

What plans do you have for your research and teaching at Leipzig University? What existing networks and projects will you be involved in?

At Leipzig University, I am interested in developing my work at the interface of climate science and ecology. Vegetation regulates the exchange of energy, water and carbon between land and atmosphere and thus contributes to the regulation of the climate system. At the same time, it is itself influenced by the climate. My goal at Leipzig University is to continue researching these bidirectional interactions and, in particular, to inspire the next generation of scientists with my teaching on these themes. For example, an exciting proposal for a Collaborative Research Centre called "Biodiversity Buffers for Climate Extremes", which we have just defended, aims to understand how biodiversity could help make ecosystems more resilient to weather and climate extremes or even mitigate the events themselves. One challenge is that such studies need to bring together scientists from many different disciplines. In our Cluster of Excellence project " Breathing Nature ", this is even more complex, as we are also collaborating with various fields from the social sciences. Leipzig University is in a unique position to achieve this due to its highly visible strong profile in Earth system research focussing on the atmosphere, biosphere and their interactions. I am very pleased to be part of these exciting developments and to now be able to help shape the Institute of Earth System Science and Remote Sensing, especially to take the students along on this journey.