Advanced terrestrial ecosystem analysis and modelling

Abstract

Ecosystems are important for human life and human livelihoods are affected when ecosystem functioning is degraded beyond some threshold. Consequently, most quantitative assessments of ecosystem dynamics have been motivated by a mix of academic curiosity and pressing resource or environmental problems. A classic case for this dualism was presented by research into the expected evolution of the impacts of acid rain in Europe during the 1980s: once the wide-spread damages became evident in Central European forests and freshwater ecosystems, stakeholders quickly began to demand a reliable risk assessment for what was perceived as an ecologically complex and dangerous situation. Scientists attempting to respond to this challenge employed a range of different approaches: while some embarked on data-rich, problem-oriented phenomenological assessments (where do the damages occur, how can they be classified, which climatic or atmospheric deposition patterns coincide, etc.), others went for a more fundamental, hypothesis-driven approach (which factors appear to be most limiting for plant performance, how does acidification work in soil and water bodies, etc.). The two approaches were never reconciled, but mitigation strategies (intentional and unintentional) appear to have been successful: with reduced acidity of rainfall, many ecosystems recovered. In addition, useful fundamental understanding of ecosystem dynamics was gathered. During the 1990s, climate and land use change were recognised as important forcings of (European) ecosystem dynamics [notably through the assessment reports of the Intergovernmental Panel on Climate Change, (IPCC)], and public and private stakeholders began to be concerned about the future functioning of forests, agricultural croplands and other ecosystems. Although the term was barely in use, the services provided by ecosystems were considered to be at risk, potentially implying economic losses compared to those experienced during the acid rain era. Funding agencies, such as the Research Directorate of the European Commission, called for a new well-structured research effort into the problem. Importantly, they directly employed IPCC terminology by defining research programmes addressing vulnerability, understood as a quantified estimate of a system’s sensitivity to the changing environment along with society’s ability to cope with the changing system. Critically, the notion of vulnerability differs from that of (expected) damage. Vulnerability assessment is intimately linked to the extrapolation of current understanding into the future, and the consideration of various scenarios to identify conditions of potential damage. Through its fifth Framework Programme on ‘‘Energy, Environment and Sustainable Development’’, the European Commission supported several integrated projects addressing vulnerability issues, one of these being the ATEAM (‘‘Advanced Terrestrial Ecosystem Analysis and Modelling’’, EVK2-2000-00075, http://www.pik-potsdam. de/ateam) project, coordinated at the Potsdam Institute for Climate Impact Research in Potsdam, Germany. ATEAM, along with its associated Concerted Action AVEC (‘‘Integrated Assessment of Vulnerable Ecosystems under Global Change’’, EVK2-2001-00074, http://www.pik-potsdam. This report was written by W. Cramer, while visiting the Centre Europeen de Recherche et d’Enseignement des Geosciences de l’Environnement (CEREGE), Aix en Provence, France—the sequence of co-authors is alphabetical.