It’s the mix that matters

Andreas Huth and Friedrich Bohn are researching how to best prepare forests for extreme events in the future.

Green leaves sway in the wind, tree limbs creak, the air is crisp and cool, and mice scurry through the foliage, all while countless birds twitter away in the treetops—the forest is a unique and important habitat for humans and animals alike. Forests cover nearly one third of the Earth’s land mass, and around one third of Germany is forested as well at 11.4 million hectares. But forests are not in good condition right now. The changing climate is hitting them hard.

For us humans, forests serve many important functions. They provide wood as a natural resource, form a habitat for many animal species, and offer people recreational spaces. Forests are also a key element in the carbon cycle: They absorb some 20 percent of the emissions caused by human activity. This means that forests through their growth — compensate for some 2 billion tons of the approximately 10 billion tons of carbon emissions that humans around the globe release into the atmosphere every year with their factories, power plants, and cars. The damage that climate change inflicts on forests reduces their ability to trap carbon.

What makes the research project unique is that it combines forest simulations and inventories with satellite measurements, enabling the researchers to draw on a wealth of global information. “People often think of James Bond movies when they hear about satellite data and all the things analyzed there using such information,” says Andreas Huth, Professor of Ecological Systems Modeling and Research Team Leader in the Department of Ecological Systems Analysis at UFZ. “But we use the data primarily to determine the forest height and forest structure, for example. Both are key input parameters for our model.” This is because they make it possible to establish the actual biomass of forests. The researchers use lidar measurements of NASA’s Global Ecosystem Dynamics Investigation (GEDI) mission for the forest structure, for instance, and radar measurements of the German Aerospace Center’s TanDEM-X mission. Combined with information about the climate and soil conditions, the researchers are thus able to analyze large forested areas, such as the Amazon. “Using our model, we can provide current information on the condition of 410 billion individual trees for this area and simulate their development for various climate scenarios,” Huth explains.

But that’s not all — FORMIND is an important tool that the scientists use to prepare large virtual forest inventories. In doing so, they systematically assess forests and simulate different types of forest use. “We work based on the forest factory approach, which enables us to test over 500,000 forests assembled on the computer and see how their structure and growth change if we increase the temperature, for example,” says Huth. “At the same time, we pay special attention to the forests’ sensitivity in responding to factors such as heat, dryness, and drought,” Friedrich Bohn,  researcher in Huth’s research group, adds. “On the basis of this data, we can then predict how existing forests will develop under different climatic conditions, for one thing. For another, we are able to make recommendations about how to cultivate and care for future forests.”

The scientist gives an example of one important recommendation: “Regarding tree types, the rule here is no more monoculture! Mixed forests are much more resistant to harmful factors,” Huth notes. “Harmful insects are often specialized in one type of tree, which means that mixed forests give them fewer targets to attack.” For this reason, Huth’s team is crafting management strategies for heterogeneously structured forests, since such forests are able to better cope with changes in climatic conditions. “Modern forestry strategies should not view the forest as a place to quickly produce wood, but rather in terms of stable and continuous production, and they need to consider biomass retention and the protection of biodiversity,” says Bohn. He adds, however, “We also have to reduce carbon emissions to prevent excessive climate change and to protect our forests.”