The aim of the paper is to develop a method to assess the effect of forest biomass use for energy on ecosystem services (ES). Such method has been in the GRASS GIS environment, by creating an Decision Support System (DSS) called r.green.biomassfor. The method has been tested in the Triglav National Park in Slovenia. The potential forest biomass was estimated with r.green.biomassfor DSS taking into account the effects of forest biomass harvesting on ES in terms of economic value. The economic value of each ecosystem service to society has been estimated using different economic evaluation methods and were spatially located with a Geographical Information System (GIS) application. Then, a semi-structured questionnaire was administered face-to-face to the experts in order to understand the effects of forest biomass harvesting on the ES at local level. Finally, the results of the questionnaire survey were elaborated to obtain indicators useful to assess the economic gain or loss on the benefits provided by ES based on the results of r.green.biomassfor DSS. (C) 2017 Elsevier Ltd. All rights reserved.