REHA - Regional study Harz

Background and Objective

As most forest ecosystem services are public goods, they do not lead to market income; nevertheless, such services are in demand within society, and the corresponding preferences can also be quantified in monetary terms. This provides an essential information basis not only for welfare economic optimisation, but also for multi-criteria analyses in this regard and, not least, for practical political decisions, for example, when it comes to using financial resources for reforestation as efficiently as possible in such a way that the various concerns of forest owners, wood processors, recreationists, water suppliers and other social groups are met as far as possible.

Most of the existing ecosystem service valuation studies are local or regional case studies, the results of which are not easily transferable to other areas (in this case, the Harz Mountains in particular). The TI-WF therefore developed the multiple benefit transfer model "ReWaLe". It is based on statistical analyses of region-specific determinants for the value of individual forest services and uses these to calculate the regional distribution of these values at district level, and in some cases also at municipal level. By varying the input data, it is also possible to simulate the influences of changed silvicultural starting conditions (insofar as these are value-determining). It currently contains modules for the evaluation of raw wood production from the perspective of society as a whole, carbon storage, local recreation and several indicators for nature conservation and landscape management services; it has a modular design so that other services that have not yet been recorded (such as drinking water protection services) can be integrated into the overall model.

Approach

The ReWaLe model is used for the environmental-economic assessment of the impacts of reforestation scenarios on recreational, nature conservation and climate protection services. For the Harz Mountains, a corresponding downscaling is carried out for adaptation with the help of regionally more differentiated input data of the forests and the population structure from the affected districts. Sensitivity analyses are used to dynamise the results (taking into account temporally changing service outputs due to forest damage and reforestation); indicators from subprojects 6-7 of the joint project are used as input variables.
The central focus of the study is on the assessment of water protection services, for which no assessment results are yet available in Germany (cf. Brouwer & Neverre 2018); the assessment approach used for this purpose was developed in the Vosges Mountains by Abildtrup et al. (2013, 2015) and has already been successfully applied in a similar way in Portugal (Lopes et al. 2018). For this purpose, the influence of the forest on the quality and quantity of the water supply in a water catchment area and its correlation with the supply costs of the regional water suppliers is determined.