In spite of the work done so far, there is still much discourse about definitions and classifications. According to Wallace (2008) a wide range of ways of evaluating trade-offs and synergies exist, but they need to be based on a coherent set of ecosystem services. However, maybe we should accept that no final classification can capture the myriad of ways in which ecosystems support human life and contribute to well-being. Since linked ecological–economic systems are complex and evolving, a ‘fit-for-purpose’ approach may be considered in creating clear classifications. Depending on the specific aim of applying a classification system the best suitable typology should be selected. Whereas some classification systems are more simple and thus well suited for educating a broad range of stakeholders (MEA, 2003), others are more complex focusing on the various spatial–temporal aspects of ecosystem services (Fisher et al., 2009). While accepting that no fundamental categories or completely unambiguous definitions exist for such complex ecosystems, and any systematisation is open to debate, it is still important to follow some basic guidelines when developing a ‘fit-for-purpose’ approach: (1) defining the overall aim/purpose of the assessment as well as the area of interest (2) be aware of the target addresser (3) be clear about the meaning of the core terms used (4) think about which services and their related indicators are important for the final assessment (5) avoid double counting and (6) the final typology should be comprehensible and balanced between different function/service groups.
Land management decisions usually relate to spatially oriented issues. To receive support for adequate choices, information on the spatial distributions of landscape functions and services is needed. A visualisation of landscape functions should also illustrate the spatial heterogeneity in quality and quantity of services provision, which is due to differences in biophysical and socio-economic conditions at different scale levels (Wiggering et al., 2006; Meyer and Grabaum, 2008). However, although recently a large number of studies have been published dealing with various assessment methods of landscape functions and services (e.g. Kienast et al., 2009; Brenner et al., 2010; Haines-Young et al., 2006; Willemen et al., 2008*) information on quantity and quality of spatially explicit services for policy relevant decisions is often lacking (Pinto-Correia et al., 2006; Vejre et al., 2007). The information that does exist remains fragmented, not comparable from one place to another, highly technical and unsuitable for policy makers, or simply unavailable (Schmeller, 2008; Scholes et al., 2008*).
Regarding the state-of-the-art, this paper shows, if the ecosystem service concept should be fully integrated into landscape planning issues, a better understanding of the interactions between land cover, use and function and methods to map and quantify land use and landscape function is needed (e.g. Verburg et al., 2009). In some cases the state of ecological knowledge and the data availability allow using some direct measures of services, while in other cases it is necessary to make use of proxies. However, finding the appropriate proxy still remains a challenge (Egoh et al., 2008; Willemen et al., 2008). By searching for appropriate indicators and proxies several issues have to be faced, especially the relationship between services and scales. Synthesizing and visualising different landscape function and services would require a spatial reference framework (Helming et al., 2008), as different function groups usually occur at different scales (for instance, while provisioning functions are often restricted to a local scale, cultural or regulating functions usually operate at a broader scale). As the provision of landscape functions mainly depends both on the quantity and the spatial configuration of the landscape elements, special emphasis have to be put on defining thresholds indicating the change of function delivery when aggregating values within different spatial scales. For instance, a special function assessed on local level, cannot be assessed in the same way at landscape level. Therefore, to extrapolate function assessments to another level, special rules have to be defined. But, most of the existing assessments still tend to provide simply aggregated values for large regions, and thus data availability and disaggregation of spatial data are still one of the major limitations to the mapping of landscape functions and services.
As landscape functions do not equally interact with one another, multifunctional landscapes have different effects on service provision (Willemen et al., 2010*). Both negative and positive effects on ecosystem service provision can be observed. Whereas some functions seem to gain by the presence of other functions (e.g. plant habitat to tourism), others are affected negatively by multifunctionality (e.g. tourism to plant habitat). Although some research has already been done on the assessment of landscape function interactions, there are still remaining knowledge gaps (Willemen et al., 2010). To analyse changes and trends in landscape function dynamics and to meet the challenges of trade-off analysis, more information on thresholds and optimum points is needed (Daugstad et al., 2006; Groot et al., 2007). In addition it would be very interesting to assess spatial and temporal scale effects on multifunctional areas (Hein et al., 2006).
Taking all these aspects into account the assessment of the full range of ecosystem values including the ecological, the economic and the socio-cultural, seems to be impossible. According to Norgaard (2010*) scientists from different research fields are used to face complex issues within different models and most of which do not fit within a stock-flow meta-framework underlying the concept of ecosystem services. We should also be aware that different disciplines often try to attain different goals, including ecological sustainability, social fairness and the traditional economic goal of efficiency. Additionally, ecological and social phenomena happen on multiple scales and over different time periods that also match with the scalars of different social institutions (Wilson et al., 1999; Folke et al., 2005). However, that the three disciplines economy, ecology and applied social studies have to cooperate and produce new relations will also lead to positive effects. Economists are increasingly aware of the importance to integrate a social point of view into their ecosystem service valuation. Because the distribution of ecosystem services directly affects many people, carefully designed discursive methods, which involve small groups of citizens in the valuation process, will help ensuring the achievement of social fairness (see Farber et al., 2002; Wilson and Howarth, 2002; Chee, 2004; Farber et al., 2006). Whereas in former decades it has been focused on either ecological or economic modelling, in recent years an integrated approach is rising, which allows directly addressing the functional value of ecosystem services by observing long-term, spatial, and dynamic linkages between ecological and economic systems (Eichner and Tschirhart, 2007). By means of cooperation of these three different approaches every part can profit from the others, leading to an integrated ecosystem valuation concept. Economics, for example, could probably better understand the complexity of ecosystems and their effects on human well-being. While, on the other side the dynamics of markets and their information flows such as money and prices as well as the trade-offs among ecosystem services are important to understand sustainable nature conservation. Thus, approaches to trade-off analysis can include multi-criteria (decision) analysis, cost-benefit analysis as well as cost effectiveness analysis. By including socio-cultural knowledge into the valuation concept, the analysis of human behaviour in its environment and human apperception of nature, will also help to enhance human welfare (Bockstael et al., 1995).
Encompassing all three disciplines into the valuation process of ecosystem services could lead to the development of a well-balanced support tool for sustainable management decisions. However, the high number of unresolved issues in quantifying and mapping of ecosystem services as well as the valuation process itself remains still as major hindrances to the implementation of the ecosystem service concept in environmental policy and management.
Besides the scientific discourse about the different valuation methods, the question of valuation regarding to
future generation will still remain as one of the main challenges. We have to be aware that evaluation of
ecosystem services can only be made within the current specific political and economic context. As
predictions about future developments are still limited, we just be able to suspect which resources are
important for future generations (Norgaard, 2010). Current values of ecosystem services should thus be
critically analysed in concordance with global, social and political change indices (Nowotny
et al., 2001). Whereas at the local and regional level the ecosystem service concept can act as a
decision support tool for stakeholder to reach sustainable land use management, at global scale
the valuation of ecosystem services can be seen as an alerting system and could encourage
rethinking the global political systems to meet future challenges, like the climate and global change
In conclusion, to meet all these challenges research effort needs to be conducted side by side to understand underlying relationships and to improve ecological as well as socio-economic understanding. Model-based research activities at local scale will take significant steps towards supplying policy makers with dependable and useable results.
As the ecosystem service research community is still very young compared to other research fields it could take some time to overcome the current barriers. However, on-going research studies, initiatives and projects, for instance the TEEB project, which are dealing with the ecosystem service approach raise hope, that the gaps get filled in the future and that the concept of ecosystem services can be integrated in environmental planning and management one time. The ecosystem service approach is an overarching concept that invites scientists from different disciplines to coordinate their research and guides their efforts towards outcomes more suitable for integration. To enhance the integration by coordinating collaborative efforts on ecosystem services at the global, national and local level a communication platform has been launched (http://www.es-partnership.org). Several international projects, for instance, the Global Earth Observation Biodiversity Observation Network GEOBON (Scholes et al., 2008) or the World Resources Institute Mainstreaming Ecosystem Services Initiative (http://www.wri.org/project/mainstreaming-ecosystem-services/tools) are developing tools and approaches to model, map and value particular ecosystem services based on abiotic, biotic and anthropogenic indicators, as well as knowledge of relationships between these factors.