Ökonomische Bewertung: Entwicklung eines Analyse- und Bewertungsrasters zur Entscheidungsunterstützung

Biological invasions have been addressed to be one of the most important sources for the loss of biodiversity (Perrings et al. 1995; Williamson 1999). Human activities and the movement of people and goods are usually taken to be the main driver of the process. International trade opens the door for many non-native plants to get introduced unintentionally (Dalmazzone 2000). On the other hand, small scale industries already exist on the base of invasive species, like the black wattle tree in South Africa (Acacia mearnsii). This tree provides firewood, timber and building material to locals and also marks an important invader in the cape fynbos vegetation (de Wit et al. 2001). Next to direct economic loss due to invasive pests in crop production, there are indirect costs of ecosystem alternations. An assessment has also to consider costs of decreasing water supply and loss of biodiversity.Thus, the complex role of an economic assessment of impacts goes far beyond the direct loss of income.For an integrated assessment of the total value of invasive species impacts, economics has to take into account two substantial premises. Firstly it has to rely on the knowledge of ecological impacts of non-native plants on ecosystems. However, the predictability of invasions is highly restricted due to variations for each single case. Therefore we have to decide under uncertainty. Secondly, even if we could determine direct ecological impacts, an integrated assessment approach still would have to deal with the problem of monetary assessment. Current research focuses on the measurement of direct costs and benefits. External effects like the loss of biodiversity and genetic resources as well as the loss of optional values are a challenge to evaluate and it is not sure that monetary values are a good measure for these effectsThe subproject "integrated economic assessment of biological invasions as decision support" aims to contribute to the development of a national strategy against invasive plants for Germany. Under the above mentioned premises the aims of the projects are:1.To review current research on economics and invasive species. What are current assessment approaches? Are there methodological shortcomings that have to be enhanced?2.To elaborate on future prevention and management strategies. A general assessment grid that takes different risk management strategies into account, will be developed as a decision support tool . 3.The assessment grid will allow an estimate of economic impacts of certain invasive species within different economic sectors. Cost-benefit  and multi-criteria analysis will be used as methods of economic assessment .As the starting point of the whole project was March 2003 there are no results to present yet.