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How is climate change affecting the world's forests? Geobotany professor provides answers in keynote talk

How is climate change affecting the world's forests? Geobotany professor provides answers in keynote talk

Photo of Professor Böhmer delivering a talk Photo of Professor Böhmer delivering a talk Photo of Professor Böhmer delivering a talk
Professor Böhmer delivers keynote talk at Klima Arena.

The Klima Arena is an interactive exhibition in Sinsheim, Germany designed to raise awareness about climate change and motivate the public to actively participate in climate change solutions. In December 2022, the venue hosted a two-day forest symposium titled, "Forestwards—Multitalented Forests under Constant Pressure." Professor Hans Jürgen Böhmer from the Institute of Geobotany at Leibniz University Hannover kickstarted the symposium with a keynote talk on how climate change is affecting the world's forests. Are we just in the continuation of a long, climate-induced forest conversion process? How is this related to the Central Europe forest dieback (Waldsterben) in the 1980s and what is the current state of global research on the effects of climate change on forests?

In his talk titled, "Everything will be different in the next forest—surprises in global forest research," Professor Böhmer spanned an arc from the climatic extremes of 2022 to the period around 1920, when a poleward shift in forest boundaries began in response to the first signs of unusual climate warming in northern Eurasia and the Americas. Using examples from his own decades of research, he described the increasingly complex impacts of climate change on the long-term dynamics of Pacific forests, among others. In this region, climate-induced forest die-offs have been part of the landscape since at least the 1970s.

On tropical islands in the Pacific, the combination of climate anomalies and altered disturbance regimes has made dense rainforests historically dominated by native species accessible to alien invasive plant species. Synergies of such biological invasions can lead to an "invasional meltdown," which can severely reduce native biodiversity and even promote the emergence of completely novel forest communities (i.e., novel ecosystems). Such invasions not only displace native plant species, but also native animal species, such as springtails that live in the soil and play a critical role in litter decomposition.

Böhmer strongly cautioned against one-dimensional thought patterns and hasty decision-making when determining the causes of forest dieback and the effects of climate change on the future behavior of tree species. The complexity of site conditions, for example in the high mountains, challenges overly simplified conclusions such as warmer climates will result in an immediate upward shift in the range boundaries of plant and animal species. A recent study in Taiwan demonstrated that tree species in mountain rainforests respond individually and unpredictably to climate change. Sweeping  conclusions about the causes of tree behavior and interrelationships in complex forest ecosystems should therefore always be critically questioned. All available knowledge, especially experiential knowledge from local stakeholders, perspectives from other disciplines, older scientific work, and historical sources, should always be taken into account.

Böhmer is very concerned about the increasing frequency of forest fires in the Mediterranean region, for example, and especially in Russia, where an area the size of Portugal fell victim to fires caused by summer drought in the last two years alone. Such large-scale disturbances release enormous amounts of CO2, which is counterproductive to international efforts to reduce greenhouse gas emissions.

English translation support by Lauren Snyder.