One query, 108,064 papers: Europe builds a shared evidence base for ecosystems

When a research consortium needs to review the scientific literature on ecosystems, the usual approach is for each team to run its own search and hope the results overlap enough to be comparable. A pan-European project funded under Horizon Europe has taken the opposite route. In the EU Horizon Research and Innovation Action SELINA — short for Science for Evidence-based and sustainabLe decIsions about NAtural capital — researchers from across the continent jointly developed a single, meticulously structured search query, the SELINA Super-Query, and applied it to two of the largest scientific literature databases in the world. The result, published as a data paper in the journal One Ecosystem, is an open-access database of 108,064 potentially relevant literature items covering ecosystem condition, ecosystem services and ecosystem accounting, all published between 2018 and 2022.

The scale of the undertaking is striking. Running the final query against Web of Science on 27 January 2023 yielded 83,950 entries; the equivalent Scopus search returned 98,574. After merging the two lists and removing duplicates based on DOIs, the refined database settled at 108,064 unique records — down from an original 182,323. Every entry carries twelve variables, including an internal identification number, article type, author information, title, publication year, journal details, DOI, abstract, author keywords, indexed keywords from Scopus, keywords generated by Web of Science, and information about duplicates and database origin. The whole dataset is stored in the Zenodo repository under the Open Data Commons Attribution License, meaning any research team, anywhere, can sub-query it for their own purposes.

Why build such a shared foundation? The motivation lies in the nature of the science itself. Ecosystem services — the benefits humans derive from nature, spanning provisioning, regulating and cultural categories — have become central to academic research and decision-making alike, particularly as climate change, land degradation and urbanisation intensify. Closely connected is the assessment of ecosystem condition, the evaluation of the quality, state or health of an ecosystem, which determines its capacity to yield services. The latest developments in both fields converge in ecosystem accounting, an integrated statistical framework provided by the System of Environmental-Economic Accounts (SEEA) Ecosystem Accounting, adopted by the United Nations, that measures ecosystem assets, their condition and the flows of services into human activity.

SELINA aims to provide robust information and guidance for stakeholder groups to support transformative change in the EU — halting biodiversity decline, supporting ecosystem restoration and securing the sustainable supply of essential ecosystem services by 2030. Yet recent literature reviews showed that the uptake of ecosystem service assessments in decision-making remains limited, both in documentation and in practice. One of the project’s motivations is therefore to improve assessment design and communication of results tailored to stakeholder needs. The project builds on the Mapping and Assessment of Ecosystems and their Services (MAES) initiative, which under the EU Biodiversity Strategy 2020 provided the conceptual, methodological, data and knowledge base for comprehensive assessments at EU-wide and Member State scales, and follows the earlier ESMERALDA EU Horizon 2020 project (2015–2018).

Within SELINA, three large systematic literature reviews are underway, each with a distinct objective: deriving a minimum set of key ecosystem condition indicators per ecosystem type; revealing how uncertainties in ecosystem service assessments relate to the likelihood of uptake in decision-making; and identifying indicators that integrate information on both ecosystem condition and services. Rather than letting each review team build its own search from scratch, the project’s task leads agreed early in 2023 to establish a common Super-Query — a broad yet precisely structured search strategy serving multiple systematic reviews simultaneously, ensuring all three tasks draw from a harmonised and comprehensive dataset.

The methodology followed a slightly modified PRISMA protocol, the standard for systematic reviews, in seven steps: creating a task force of eight members drawn from the review leads and the SELINA Knowledge and Data Flows team, with expertise spanning environmental science, landscape ecology, landscape planning, physical geography and environmental economics; defining the scope; identifying key concepts, keywords and synonyms; developing the query string; fine-tuning and testing; running and recording the final query; and processing the harvested literature into the final database. The task force agreed to apply the Super-Query to Web of Science and Scopus, restricted to English-language, peer-reviewed articles published between 2018 and 2022 — capturing the most recent developments since ESMERALDA concluded.

The technical construction of the query reveals the depth of the challenge. Three general concepts were addressed: ecosystem services and nature’s contributions to people; ecosystem condition; and ecosystem accounting. For each, the team compiled general keywords, synonyms, spelling considerations and truncations with wildcards to capture word variations — for example, adding various terrestrial and aquatic ecosystem types as alternative terms for ecosystem condition. Controlled vocabulary and restrictive terms were included to limit findings to genuine assessments rather than papers that merely drop the terminology. The restrictive terms for ecosystem services list assessment methods, adopted from the IPBES values assessment and extended by 36 methods identified in ESMERALDA; those for ecosystem condition relate to specific measurement and evaluation keywords.

The iterative refinement process was equally revealing. An online tabular spreadsheet with semi-automated functionality merged individual keyword sections through predefined formulae, dynamically updating query combinations whenever keyword sets were modified, and even providing estimates of the potential volume of literature items per combination. An automated translation mechanism converted Web of Science query syntax into the corresponding Scopus format, adjusting field tags and operators — for instance, converting the proximity operator NEAR/10 to Scopus’s W/10. Notably, the two databases define their combined search fields differently: Web of Science’s Topic Search field includes Author Keywords and KeyWords Plus, terms generated from the titles of cited references, while Scopus’s TITLE-ABS-KEY field includes Author Keywords, Index Terms, Trade Names and Chemical Names, leading to differences in the scope and nature of results retrieved from each.

Fine-tuning exposed a common pitfall of large literature searches: many papers use ecosystem service or ecosystem condition concepts in their keywords without properly addressing them in content. Initially, querying ecosystem condition terms alone yielded more than one million entries; adding restrictive terms aimed at ensuring a proper assessment reduced the number to one tenth. The final search string comprises six search units — ecosystem services and nature’s contributions to people, ecosystem service synonyms, ecosystem service restrictions, ecosystem accounting, ecosystem condition, and ecosystem condition restrictions — all connected with the Boolean operator AND, with terms within each unit generally connected by OR. In two units, the NEAR/10 proximity operator connects ecosystem types to analogies of condition or service, maintaining semantic accuracy across the vast keyword space.

The profound collaboration of review task leads in this early phase of the project led to the successful compilation of the operational Super-Query database, a fundamental resource for the succeeding literature reviews. Review task leads will continue to sub-query relevant literature and proceed with their specific objectives, while the agreement on consistent terminology lays an important foundation for further collaboration within the consortium. Approximately 6,200 entries without a DOI remain in the database, so users are advised to perform additional duplicate removal based on identical titles after sub-querying. Beyond SELINA, the co-creation process has created a valuable resource to be used by the project and beyond — a single, transparent, reproducible search strategy that any team studying ecosystem condition, services or accounting can now build upon.

Subject of Research: Development of the "SELINA Super-Query" in a pan-European Horizon Europe project: A systematic literature search on Ecosystem Condition, Ecosystem Services and Ecosystem Accounting

Article Title: Development of the "SELINA Super-Query" in a pan-European Horizon Europe project: A systematic literature search on Ecosystem Condition, Ecosystem Services and Ecosystem Accounting

Article References: Seguin, J., Lange, S., Barton, D., Grêt-Regamey, A., Rendón, P., Roche, P., Nicholson Thomas, I., & Burkhard, B. (2025). Development of the "SELINA Super-Query" in a pan-European Horizon Europe project: A systematic literature search on Ecosystem Condition, Ecosystem Services and Ecosystem Accounting. One Ecosystem, 10, Article e155968. https://doi.org/10.3897/oneeco.10.e155968

Image Credits: AI Generated

DOI: 10.3897/oneeco.10.e155968

Keywords: Development, SELINA, Super-Query, pan-European, Horizon, Europe, project, systematic, literature, search, Ecosystem, Condition