DGGM-Lecture
Die Deutsche Gesellschaft für Geomorphologie (DGGM) wurde 2021 aus dem DGfG-Arbeitskreis Geomorphologie heraus gegründet. Sie vernetzt die Geomorphologie auf (inter)nationaler Ebene in der Forschung, der Nachwuchsförderung und in der (geographischen) Ausbildung an Schulen und Universitäten.
Fire in the Earth System: Perceptions and realities in a changing world
Wildfire has been an important process affecting the Earth’s surface and atmosphere for over 350 million years, with human societies having coexisted with fire since their emergence. Yet many now consider wildfire as an accelerating problem, with widely held perceptions both in the media and scientific papers of increasing fire occurrence, severity and resulting losses.
The evidence underpinning these perceptions appears contradictory. When examining global and regional trends in fire activity over the last two decades (2001-2019) and the role of the frequency and intensity of fire weather in the observed trends, we find that significant increases in fire weather have occurred in most world regions due to climate change. On average, the fire weather season has lengthened by 27% globally. This increase has been even greater than climate models have predicted in some of the major fire regions. A range of other bioclimatic and human factors, however, have counteracted those of fire weather, causing a net global decrease in the area burned by around one-quarter (1.1 million km²) in the last two decades. Much of the decrease (590,000 km²) has been in African savannahs, where 60-70% of the annual global area burned occurs. In many areas of the world, the number of fires has also decreased, leading some to erroneously perceive that climate change is not affecting wildfire occurrence. In most forested regions of the world, however, where fires are often most consequential in terms of impacts on ecosystems, society or emissions, the area burned has increased. For example, by 21,400 km² (93%) in east Siberian forests and by 3,400 km² (54%) in the forests of western North America since 2001. Extensive forest fires are now even a concern in areas such as Germany where they have been historically rare.
Weather conditions affecting vegetation growth and the buildup of fuels, the presence of human ignitions in regions that are not naturally fire-prone, and the fragmentation of fire-prone landscapes by agriculture are key factors that locally or regionally still appear to outweigh climate and resulting fire weather as current controls on fire activity. Climate models agree, however, that fire weather will become increasingly frequent and intense under future warming, and at an increasing rate with each additional increment of warming. It is thus likely that the role of fire weather will become a more dominant factor in controlling fire activity. To what degree land management will be able to counteract this increasing threat is unclear and it is likely that current approaches may not remain effective in the future.
This presentation aims to examine (i) the impacts of climate and human activity on global fire trends and impacts, (ii) the often contrasting perceptions about fire, and (iii) the options society has in co-existing with fire risk under our warming climate.
Stefan Doerr ist Professor für Waldbrandwissenschaft und konzentriert sich auf grundlegende und angewandte Fragen zu den Auswirkungen von Bränden auf die Kohlenstoffdynamik von Landschaften, auf Böden und Wasserqualität, Ökosystemleistungen sowie auf globale Brandmuster, Trends, Risiken und soziale Wahrnehmungen. Sein spezielles Interesse gilt u.a. der Bodenhydrologie und Erosionsdynamik durch Veränderungen von Infiltration.