The ecosystem services concept, which frames nature’s benefits to people in terms of provisioning services such as food and timber, regulating services such as flood control and water purification, and cultural services such as recreation and aesthetic value, has become the predominant paradigm for environmental research and policy-making since the foundational works of De Groot, Costanza, and Daily in the 1990s and the Millennium Ecosystem Assessment in 2005. The idea provides a methodological bridge linking the condition of ecosystems to human well-being, a platform for solving environmental problems that spans the natural and social sciences. That interdisciplinarity, however, also means publications scatter across disciplines, apply wildly different methods, and use the ecosystem services label for widely different aims, making it hard for researchers and policy-makers to judge the credibility of results or compare studies. Systematizing that accumulating knowledge is precisely what the Bulgarian team set out to do.

The review collected every available published work on ecosystem services authored or co-authored by Bulgarian geographers, screening an initial pool of 145 publications down to 123 that genuinely address the topic. To characterize this corpus, the researchers constructed a special database with a standard nomenclature, a structured template covering five main parts: general characteristics of each publication, the ecosystem services studied, the methods applied, the case study, and the mapping. Variables were entered as binary numerical values where possible, otherwise as text. The services were classified into the three main groups of provisioning, regulating, and cultural following the CICES classification, and methods were sorted into the three major categories of biophysical, social, and economic assessment.

The retrospective analysis revealed four distinct stages in the development of the field. The first steps, from 2005 to 2010, came through two pioneering projects: a joint initiative of the United Nations Development Program and the Ministry of Agriculture and Food on protecting globally significant biodiversity in the Rhodopes, which produced the first Bulgarian publication on ecosystem services in 2007, and the international project on landscape sciences for environmental assessment, whose participation by researchers from the Institute of Geography of the Bulgarian Academy of Sciences led to the first research paper applying hydrological models to flood regulation assessment in 2008. The second stage, from 2010 to 2014, saw significant development of research methods, with biophysical approaches for mapping flood regulation through GIS-based hydrological modeling applied in several case studies and economic valuation methods, especially contingent valuation, tested mainly at the municipality level. These works fed into international developments, contributing to the matrix approach for mapping and to blueprints of mapping and modeling methods.

The third stage, from 2014 to 2018, was defined by the MAES process itself. In response to EU requirements, the Bulgarian Ministry of Environment and Waters initiated a national program for mapping ecosystems, gathering researchers from various disciplines and institutions to develop methodologies for each of the nine main ecosystem types. These activities produced a national information system for ecosystems, numerous publications, a special issue in the journal One Ecosystem, and contributions to the European-level methodology through systematization of biophysical methods, comparative analyses, and updates of the methodological framework. The post-MAES period after 2018 brought further development of specific fields, including the impact of climate change on ecosystem services, ecosystem accounting, nature-based sustainable tourism, nature heritage in forest areas, and the integration of nature-based solutions, although the end of the national program led some participants to drift away from the field.

The profile of the 123 publications is telling. Research and review papers in scientific journals form the largest category at 40 percent, followed by conference proceedings at 19 percent and book chapters at 14 percent, with methodologies, doctoral dissertations, and other types making up the rest. Publication activity peaked in 2017 and 2021, years when two national projects, the ESMERALDA mapping projects under the MAES framework and the Heritage.BG project, came to an end. Only 43 percent of the publications are indexed in Scopus or Web of Science, while 57 percent are not, and although 66 percent are available online with open access, 15 percent count as grey literature that does not appear online at all. English dominates as the publishing language at 69 percent, with Bulgarian at 21 percent and only 10 percent bilingual. The most prolific outlets are the Journal of the Bulgarian Geographical Society with 16 papers, One Ecosystem with 13, and a publishing house with 11 methodologies.

Authorship is heavily concentrated. Researchers from the National Institute of Geophysics, Geodesy and Geography at the Bulgarian Academy of Sciences lead 41 percent of the publications and Sofia University 26 percent, while only 9 percent are led by foreign authors. Shumen University is the only studied institution with zero authors publishing on the topic. The most active lead author has 19 publications, followed by another with 10. International collaboration remains limited: only 18 percent of the publications have foreign co-authors, with Germany the most frequent partner at 15 publications, followed by Spain with six. Outside Europe, only Australia and the USA appear. The case studies, however, reach further: 70 percent of the publications have clearly defined, spatially outlined case studies, predominantly local in scale, covering 109 sites in total, 97 of them in Bulgaria and the rest in ten other countries across three continents. The largest cluster of local case studies, 19 of them, lies around the Central Balkan National Park, and municipalities and river basins emerge as the most popular spatial units.

On the substance of the research, 64 percent of the publications performed actual ecosystem services assessment, while the rest were conceptual papers, editorials, ecosystem mapping studies, or broader environmental works that merely mention the concept. Regulating services are the most studied group at 50 percent overall, followed by provisioning at 38 percent and cultural at 35 percent. Biophysical methods dominate the assessment toolkit at 62 percent, with social and economic methods each at 19 percent. Mapping is present in 47 percent of all sources and 59 percent of research papers, with biophysical studies far more likely to contain maps, at 78 percent for research papers, compared with only one-third for economic studies. The share of publications without maps has steadily declined across the four periods, from 83 percent in the first to 47 percent in the last, a trend the authors attribute to the MAES process and to the activities of the Ecosystem Services Partnership working group on mapping and modeling, in which Bulgarian geographers were active participants.

The review exposes clear gaps. Studies overwhelmingly assess supply, at 59 percent, while research on demand and on the supply-demand balance remains scarce, a disproportion that mirrors the dominance of biophysical methods at the expense of social and economic approaches, which are more appropriate for demand studies. Natural objects such as mountains and lakes are popular case studies, but their boundaries vary case by case and hardly correspond across studies, limiting policy uptake, while nature protection areas are rarely selected at all. The predominance of local case studies and the scarcity of multiscale research suggest researchers prefer small areas where data and expertise are easily available, and the national mapping under MAES produced mainly methodological publications whose real-world applicability is still to be proved, with few results published in high-ranked journals.

From these findings the authors define the priorities for the coming years. The main priority is developing the spatial aspects of methodological frameworks for mapping and assessment, including identifying relevant scales for particular indicators, stating precisely the spatial scale and extent of assessments, defining spatial units more clearly, applying more spatially explicit indicators including those for ecosystem condition, and conducting sensitivity analyses of varying spatial resolutions and potential trade-offs between scales. The next priority is better use of GIS-based tools, particularly specialized software such as InVEST, ESTIMAP, and ARIES, alongside models’ integration that could also incorporate more social and economic methods and help overcome the demand-side gap. Finally, the authors call for improved publication quality and more papers in highly rated indexed journals, achieved by focusing on internationally recognized topics, applying modern methods, and abandoning grey literature as a publication option. Despite two decades of progress that saw Bulgarian geographers take a leading role in mapping ecosystem services across all its spatial aspects, the field in the country is still relatively new, and filling these gaps will determine whether it fully comes of age.

Subject of Research: Twenty years of ecosystem services research in Bulgaria analyzed from a geographical perspective

Article Title: Twenty years of ecosystem services research in Bulgaria: lessons learned and future directions from a geographical perspective

Article References: Nedkov, S., Stoycheva, V., Prodanova, H., Ananiev, I., & Yordanov, Y. (2024). Twenty years of ecosystem services research in Bulgaria: lessons learned and future directions from a geographical perspective. BioRisk, 22, 33-52. https://doi.org/10.3897/biorisk.22.125194

Image Credits: AI Generated

DOI: 10.3897/biorisk.22.125194

Keywords: ecosystem services, Bulgaria, geography, MAES, mapping, GIS, biodiversity, EU Biodiversity Strategy, Twenty, years, ecosystem, services