Mapping Istanbul’s Ecosystem Services Reveals the Hidden Cost of Urban Growth

Every land-use decision a city makes is also a decision about nature. When forests are cleared for housing or wetlands are drained for infrastructure, the services those ecosystems provide — clean water, flood regulation, crop pollination, cooling shade — quietly disappear. A new study published in the journal One Ecosystem argues that these losses are not inevitable, and that a mapping technique called Integrated Ecosystem Services potential can give urban planners a practical, quantifiable way to see the consequences of their choices before they are locked into concrete. Using Istanbul, one of the fastest-growing megacities in the world, as its testing ground, the research shows how ecosystem service knowledge could be woven directly into the machinery of spatial planning.

The stakes are enormous. According to the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services, land-use and land-cover decisions have already degraded ecosystems to the point where the well-being of roughly 3.2 billion people is negatively affected, and the economic value of lost biodiversity and ecosystem services amounts to around 10 percent of global annual gross domestic product. The United Nations has emphasized that healthy ecosystems can deliver about 37 percent of the mitigation needed to limit global temperature rise, making their protection a matter of climate strategy as much as conservation. Yet despite a rich scientific literature on ecosystem services, researchers have repeatedly identified a stubborn gap between what science knows and what planners actually use.

The study, led by researchers examining Turkey’s largest city, tackles that gap head-on. Its central tool is the Integrated Ecosystem Services approach, built on a widely used matrix method that links each land-cover class to a supply capacity score for individual ecosystem services, ranging from zero for no potential to five for very high potential. By averaging these scores across all services — treating each as equally important — the method produces a single Integrated Ecosystem Services potential value for every parcel of land. Areas with high or very high potential represent the most functional landscapes for sustaining ecosystem services, adapting to climate risks and supporting sustainable development. The appeal of the approach lies in its simplicity: it is easy to understand, easy to compute in standard GIS software, and easy to communicate to decision-makers who are not ecologists.

To test how different planning philosophies would reshape Istanbul’s ecological backbone, the team modelled four land-use scenarios using the Scenario Generator Model of the InVEST software suite, working from CORINE land-cover data. The Business-as-Usual Scenario assumes that the land-use changes observed between 1990 and 2018 simply continue, with expanding urban areas and rising pressure on natural resources. The Climate Change Adaptation Scenario assumes moderate population growth, minimal urban expansion and the prioritized protection and rehabilitation of natural areas. The Maximum Development Scenario projects the continuation of current trends plus the mega-projects inscribed in Istanbul’s 2020 Revision Environmental Master Plan. Finally, the Maximum Conservation Scenario assumes that population and urbanized areas stabilize and that protecting natural land becomes the dominant priority.

The results are striking. Compared with the current situation, the Maximum Development Scenario produces sharp declines of 6.87 percent in high Integrated Ecosystem Services potential areas and 6.14 percent in very high potential areas — the landscapes most critical for ecosystem sustainability. In that same scenario, artificial surfaces expand from 26.82 percent to 30.46 percent of the city’s area, while agricultural land, forests and semi-natural areas, and waterbodies and wetlands all shrink. The most notable spatial losses cluster around the zone where the Canal Istanbul project is planned, a vivid illustration of how a single infrastructure decision can erode a city’s ecological capacity. By contrast, the Maximum Conservation Scenario delivers the largest gains, increasing high potential areas by 2.16 percent and very high potential areas by 9.68 percent, with the Climate Change Adaptation Scenario producing similar, if somewhat smaller, improvements.

What makes these findings more than an academic exercise is the way the maps translate abstract ecological trade-offs into the visual and quantitative language of planning. Development-driven scenarios systematically trade high-potential areas for low and very low ones; conservation-driven scenarios do the reverse. Because the method quantifies both the amount and the location of change, planners can compare alternative futures side by side and see exactly which districts would gain or lose ecological functionality under each option. The authors argue that this capacity to interpret the consequences of different spatial decisions as impacts on integrated ecosystem services potential demonstrates that the ecosystem services concept is not merely relevant to spatial decision-making — it is intimately bound up with it.

The study also takes an unflinching look at how much of this knowledge has actually penetrated Turkish law and practice. Sectoral policies contain general targets for identifying, protecting, monitoring and evaluating ecosystem services, but without a methodological framework these targets remain largely aspirational. There is no legal obligation in Turkey’s spatial planning legislation to integrate ecosystem services, and implementation examples are rare. The clearest exceptions are the special provision determination projects for the Büyükçekmece and Melen dam lake watersheds, where ecosystem service mapping was used to delineate water-related protection zones under the Regulation on the Protection of Drinking-Irrigation Water Basins. Forest management plans incorporate ecosystem services indirectly, treating them as economic, ecological and socio-cultural functions under a 2017 communiqué from the General Directorate of Forestry. Meanwhile, the National Spatial Strategy Plan, still in preparation, is the first national-level planning effort to map critical integrated ecosystem services areas nationwide and to calculate per-capita indicators for both ecosystem services and climate adaptation.

Building on this analysis, the researchers propose a concrete roadmap for Istanbul’s high-level plans. They organize ecosystem service knowledge into three modes of use recognized in the research community: conceptual use, which communicates the importance of nature to society; strategic use, which advocates specific policies and resolves stakeholder conflicts; and instrumental use, which supplies technical tools for selecting the best interventions. In the Regional Plan, ecosystem services could inform preliminary strategies, current situation analyses and stakeholder meetings, and could sharpen the existing Green Transformation vision — for example, by adding performance indicators such as the ratio of critically significant ecosystem service areas to the city’s total area, or per-capita measures of high-potential land. In the Environmental Master Plan, whose central philosophy is resolving conflicts between the natural and built environment, ecosystem service concepts could structure the SWOT analysis, define protection degrees in the Natural Threshold Synthesis, and generate a green-blue network map for the Spatial Sustainability Synthesis.

The authors are candid about the limitations of their framework. The CORINE land-cover data they used offers limited spatial detail, and a more location-specific dataset — such as forest management information — would yield more realistic results. The assessment captures only the potential, or supply, side of ecosystem services; a more holistic approach would also account for demand and flows, meaning the services people actually use. The equal weighting of all services is another simplification, and stakeholder-driven prioritization could change which areas appear critical. Past projects in Turkey, such as the Ömerli Basin integrated watershed management initiative, show that stakeholder workshops can successfully rank ecosystem service priorities and identify areas vulnerable to climate change and urbanization. Participatory scenario planning, the authors suggest, would strengthen the entire process and improve the odds that final plans are adopted by all parties.

Even with these caveats, the study’s core message lands with force: ecosystem services can be quantified, mapped and embedded in every stage of spatial planning, from stakeholder dialogue to statutory plan decisions. In a world where land-use change is projected to keep degrading ecosystems through 2050 and beyond under business-as-usual pathways, tools that make ecological trade-offs visible before decisions are made may be among the last, best hopes for making conservation a genuine priority in planning. For Istanbul — a city straddling two continents, growing relentlessly, and contemplating mega-projects that could reshape its landscapes — the maps produced in this research offer something rare: a way to see the future of its nature before that future is built.

Subject of Research: Integration of ecosystem services assessment into urban spatial planning and land-use decision-making in Istanbul

Article Title: Contribution of integrated ecosystem services to urban planning tools: Can it be more functional for the sustainability of ecosystems?

Article References: Türkay, Z., & Tezer, A. (2024). Contribution of integrated ecosystem services to urban planning tools: Can it be more functional for the sustainability of ecosystems?. One Ecosystem, 9, Article e121553. https://doi.org/10.3897/oneeco.9.e121553

Image Credits: AI Generated

DOI: 10.3897/oneeco.9.e121553

Keywords: ecosystem services, urban planning, Istanbul, land-use change, scenario analysis, sustainable development, climate change adaptation, spatial decision-making, biodiversity, InVEST, CORINE, ecosystem services mapping