A multi-tiered approach to map and assess the natural heritage potential to provide ecosystem services at a national level

Natural heritage (NH) possesses an outstanding universal value that can be described as "natural significance" at a national level. The ecosystems can be considered as the spatial units which represent the NH of the particular area in terms of their value to people. Recreation and tourism are amongst the important values which are strongly dependent on the NH and they have a certain impact on the ecosystems' condition and the quality of the services they provide. The efforts through the Mapping and Assessment of Ecosystems and thier Services (MAES) process led to the development of a multi-tiered approach that considers different methods at different levels of detail and complexity and can be applied according to specific needs, data and resource availability. In this paper, we propose the development of this methodology for the specific need for mapping and assessment of the NH as a source of ecosystem services (ES) for recreation and tourism. The conceptual scheme of the study demonstrates how the MAES framework can be adapted to the specific needs of the work and arrange the methods into three tiers according to the data availability and resources. The mapping and assessment procedure is based on an algorithm for spatial data analyses which enables the evaluation of the NH potential to provide 15 ecosystem services. The results show that the NH of Bulgaria is a valuable source of ES which are well presented in most parts of the country. The areas with very high potential form several clusters that correspond to the country's tourist regions. The proposed approach is applicable on the national scale and solves the problem of data availability limitations for various ES. The algorithm ensures the optimal quality of the results using the available data and resources. Instead of an expert-based assessment for all services which is easier, but less accurate, the proposed approach provides the means how to define more precise indicators, based on statistical data or models where possible. The study provides appropriate data for analyses of the methods' performance at different tiers