Ecosystem services in human-environment systems: What is the problem? Ecosystems deliver goods and services of enormous value to the human society (Pearce and Moran, 1994; Costanza et al., 1997; Daily, 1997). However, intensive land and water use, extraction of natural resources, and chemical emissions into the environment lead to a worldwide degradation of biodiversity and of the supporting services, provisioning services, regulating services and cultural services which ecosystems provide (Hooper et al., 2005; Millennium Ecosystem Assessment, 2005b). On a global scale the Millennium Ecosystem Assessment (2005b) found that 60% of global ecosystem services (ES) surveyed are currently being degraded or used unsustainably. Future scenarios are promising no relieve. Only the projected doubling of food consumption for the next 50 years (Tilman et al., 2002), in combination with the growing demand for biofuels and other biophysical products will challenge decision-makers dealing with ecosystem management worldwide. They need to optimize ecosystems with respect to multiple needs. Climate change has even intensified the dynamics of this human-environment interaction (McCarthy et al., 2001).

Ecosystem services are defined as functions of ecosystems with value for human well-being. Thus the concept of ecosystem services, establishes a relationship between ecosystem service suppliers (the producers) and demanders for ecosystem services (the beneficiaries). Those supply-demand interaction can be distinguished on three levels: i) upstream – downstream relations, ii) north – south relations and iii) poor – rich relations.

i) Because of topographical complexity and altitudinal gradients mountain ecosystems are particularly sensitive to global change compared to the lowland (Becker et al., 2007; Bugmann et al., 2007). Socio-economic vulnerability to loss of ecosystem services tends also to be higher because of generally more difficult socio-economic conditions in mountains. But also the lowlands are influenced by undesired changes in mountain areas, because of their importance for biodiversity and for providing ecosystem services. Downstream actors benefit from the supply of upstream ecosystems with respect to clean water, flood control, reduced sedimentation, scenic beauty and many more positive mountainous ecosystem services.

ii) Similarly, pressure on ecosystem services is high in the south because of continuous land use change, land degradation and impacts of climate change. Until now, such damages to ecosystems services are not sufficiently taken into account in the environmental decisions along the global value chains linking consumer, retailer, processor, and producer in the north and the south. Fair trade is a first step into this direction, but global trade basically masks the constraints of regional ecosystems. To increase the ecological transparency and foster sustainable ecosystem management, the involved public and private actors need to develop, improve and use instruments for ecological assessment and management of global value chains damaging regional ecosystem services. Lately ideas have been developed for international payments for ecosystem services and international biodiversity off-sets (see for a review in German or French language Koellner and Engel, 2008b; Koellner and Engel, 2008a).

iii)In both cases mentioned before the relationship between upstream-downstream and north-south are potentially equivalent to a poor-rich relationship. Especially in developing countries with weak environmental legislation and enforcement, the activities of the primary sector (agriculture, forestry, fisheries and aquaculture, but also oil, gas and mining) lead to deforestation, cause severe damages to biodiversity and finally limit the capacity of ecosystems to deliver bundles of services at the landscape scale to the local people. This is especially objectionable, if biotic resources are produced unsustainably in poor countries in the south and exported to rich countries in the north with strict environmental regulation, but only for the own territory. I am not saying that global trade per se is bad for the environment, but innovative solutions are needed if the poor are affected, because they cannot buffer losses of ecosystem services with purchased human-made services. To replace missing legislation pro-poor payments for ecosystem services were discussed in the past (Landell-Mills and Porras, 2002; Duraiappah, 2006; Ravnborg et al., 2007; Bulte et al., 2008; Proctor et al., 2008; Tallis et al., 2008).

To successfully manage such supply-demand relations for ecosystem services under pressure of global change requires a collaboration of science and practice. New strategies for local, regional and global management of ecosystems are necessary, which are based on ecosystem services quantification; design of finance, policy and governance systems; and the implementation of those in various biophysical and social contexts (Daily and Matson, 2008).

Within this general framework the three main objectives of my habilitation thesis on Ecosystem

Services in Human-Environment Systems are Part A) to model land use and its impact on biodiversity and ecosystems and their services Part B) to analyze the decision-making that drives supply and demand for ecosystem services, and Part C) to explore the ecosystem impact of the financial sector national and international payments

for ecosystem services (PES) and their linkages to the financial sector.

In this introduction I reflect first the recent discussion about the definition of ecosystem services. Then I develop a general framework to organize research on ecosystem services. Finally, for each of the three objectives I provide a short review of existing research and describe my contribution to fill the gap.

What are ecosystem services? Much confusion about their definition.

Daily (1997) and the contributing authors from natural and social sciences introduced the term and concept of ecosystem services in order to stress the dependency of human-well being on nature. This milestone work defines ecosystem services on page 3 as follows: “Ecosystem services are the conditions and processes through which natural ecosystems, and the species that make them up sustain and fulfill human life. They maintain biodiversity and the production of ecosystem goods, such as seafood, forage, timber, biomass fuels, natural fiber, and many pharmaceuticals, industrial products, and their precursors.” (Daily, 1997, page 3). In this definition ecosystem goods and biodiversity are an output of natural functions in sensu de Groot (1992).

Interestingly, the Millennium Ecosystem Assessment MA (2005b) skips the distinction between tangible ecosystem goods. It defines ecosystem services broadly as the “benefits people obtain from ecosystems”. It does distinguish supportive services (like nutrient cycling and soil formation), provisioning services (like food, fresh water and fibers), regulating services (like erosion control or water purification), and cultural services (like provision of opportunities for recreation and spiritual or historical purposes). That means what is a good under the definition of Daily is in the MA defined as an ecosystem services. Exactly around this issue, there is currently a scientific debate ongoing (see Boyd, 2007; Boyd and Banzhaf, 2007; Wallace, 2007; Costanza, 2008; Fisher and Turner, 2008; Wallace, 2008).