Dry subtropics reveal stark imbalances in ecosystem service research

Ecosystem services — the benefits that people derive from living systems, from food and fuel to flood protection and spiritual solace — have become one of the fastest-growing fields in environmental science. Yet a new systematic review published in One Ecosystem shows that this growth is strikingly uneven across the world’s dry subtropical regions, and that the scientific literature there bears only a loose relationship to the actual pressures that local populations place on nature.

The review, which analysed 471 publications drawn from the Scopus and SciELO databases, offers one of the first systematic portraits of how ecosystem service science has developed across the world’s dry subtropical belts. These regions, defined by the authors using a consistent biophysical template, share dry winters, wet summers, mild mean annual temperatures between 20 and 25 degrees Celsius, semi-arid to sub-humid water balances, low altitudes and flat terrain. Together they cover roughly 6.4 million square kilometres, about five percent of the global land surface excluding Antarctica, and were originally dominated by woodlands and savannahs. Five regions met these criteria: the Zambezi-Kalahari in Africa, the India-Pakistan region in southern Asia, north-eastern Australia, the Mesquite region of North America and the Chaco of South America.

Because these five regions share such similar climatic and topographic conditions, they provide an unusually clean natural experiment for studying how human factors shape scientific attention. If research effort simply tracked environmental conditions, one might expect the literature to be distributed roughly evenly across them. Instead, the review found that more than 60 percent of publications focused on the African dry subtropics, followed by the South and North American regions, while studies from southern Asia and north-eastern Australia were comparatively scarce. This skew is all the more striking given that the regions differ enormously in population density, agricultural intensity, wealth and cultural values, attributes that might plausibly be expected to drive demand for ecosystem service knowledge.

Thematically, the literature is dominated by provisioning services, the material benefits that ecosystems supply such as food, fodder, timber and fuel. Some 53 percent of the reviewed publications addressed this category, while cultural services appeared in 33 percent and regulating services in 30 percent. These proportions reveal a field still anchored in questions of direct resource use, which is perhaps unsurprising in regions where many rural livelihoods depend heavily on firewood, grazing land and wild products. Yet the relatively strong showing of cultural services suggests that researchers in these regions are also attentive to recreation, heritage, spiritual values and the non-material dimensions of human-nature relationships.

Two structural features of the literature stand out. First, only 13 percent of publications addressed more than one ecosystem service category, indicating that most studies remain narrowly focused rather than adopting the integrated, multi-service perspective that many frameworks advocate. Second, approximately one third of the publications mentioned economic valuation, meaning that monetary approaches, while present, are far from universal. This matters because valuation is often the pathway through which ecosystem service research enters policy debates, informing decisions about land-use planning, compensation schemes and infrastructure development. A literature in which two thirds of studies avoid monetary framing may engage differently with decision-makers than one dominated by cost-benefit analysis.

Temporally, the review documents a clear inflection point. Research on ecosystem services in the dry subtropics increased significantly from 2005 onwards, a timing that coincides with the publication of the Millennium Ecosystem Assessment, the global synthesis that popularised the ecosystem service concept and its classification into provisioning, regulating, cultural and supporting categories. The authors followed this classification in their own review, with minor adaptations such as renaming the fibre category as material and fuel and folding educational values into cultural services. Roughly 45 percent of the reviewed publications actually used the term ecosystem service, and the frequency of that term rose substantially over time, confirming that the vocabulary of the field has progressively penetrated research on these regions even where it was not initially adopted.

The methodological choices of the review are worth noting for what they exclude as well as include. The authors restricted their analysis to services provided by woody-dominated systems, including forests, woodlands, shrublands, savannahs, woody wetlands and woody steppes, and discarded studies of cultivated, coastal or urban ecosystems. They also excluded supporting services such as productivity, soil formation and nutrient cycling, treating these as intermediate services whose benefits to people are indirect, following established conventions in the ecosystem service literature. Theoretical contributions, biodiversity studies and remote-sensing analyses linked only to ecosystem properties were likewise set aside. These boundaries sharpen the focus on services with direct human beneficiaries but also mean that the picture presented is deliberately partial, concentrated on the woody vegetation that characterises these landscapes.

The databases themselves shape the geography of what was found. Scopus is a proprietary index covering tens of millions of records worldwide, while SciELO is a free-access repository of Ibero-American and South African journals publishing in Spanish, Portuguese and English. Including SciELO was a deliberate choice to capture research published in regional journals that international indexes often miss, particularly from Latin America. Even so, the scarcity of publications from the India-Pakistan dry subtropics suggests that language, indexing and institutional factors may still filter which research becomes visible to a global review of this kind. The authors themselves caution that research efforts appear to be influenced by a diverse range of financial and institutional constraints, international research agendas and the personal interests of researchers, giving the field an idiosyncratic character.

Perhaps the most conceptually interesting finding is what the review failed to find. The authors had formulated explicit predictions linking research patterns to human pressures. They expected provisioning services to predominate in contexts of high population density, low affluence and high isolation from markets, reasoning that such conditions increase local reliance on natural resources. They expected regulating services to dominate where land-cover transformation is high and market access easy, anticipating concern about the loss of functions such as flood mitigation and climate regulation. And they anticipated more cultural service studies in areas retaining extensive uncultivated land and protected areas. None of these predictions was clearly supported. The analysis found no clear relationship between the number of publications, publication density or thematic representativeness and the variables used as indicators of human pressure, including population density.

This null result is more informative than it might first appear. It suggests that the geography of ecosystem service research is not simply a mirror of environmental need or demographic pressure. Wealthier regions may have more resources to fund research regardless of local dependence on nature, while poorer, more isolated regions with the greatest direct reliance on firewood, wild foods and grazing may be studied least. International funding priorities, the location of research institutions, the presence of long-term ecological research sites, colonial and post-colonial scientific ties, and the individual interests of researchers all appear to leave their imprint on where studies are conducted and what questions they ask.

The conceptual framing of the review draws on the ecosystem service cascade, a widely used model that distinguishes ecological structures and functions from the services they generate and the benefits people ultimately receive. A woodland, for example, may have the capacity to reduce surface runoff, a regulating function that produces the benefit of lower flood risk. Whether that function counts as a service, the authors note, depends on the value society assigns to the benefit. This distinction is central to understanding why regions with similar environments might develop different research traditions: perception of benefits varies with society’s needs, land-use choices and moral values, including religious and emotional attachments, and these perceptions in turn shape the questions scientists pursue and the agendas that governments set.

The dry subtropics are an especially apt setting for exploring such variation because, despite their shared biophysics, they display some of the most pronounced cultural disparities found within any single biome. Agriculture ranges from subsistence production to industrial commodity cultivation, and the fate of what is produced varies accordingly. Population growth, rising affluence and integration into global markets are intensifying pressures on natural resources across all five regions, but the capacity of local populations to appropriate resources, and the ability of external actors such as tourists and agribusiness companies to enter and exploit them, differ sharply with affluence and geographic isolation.

For the research community, the review identifies gaps that are both geographic and thematic. The underrepresentation of southern Asia and north-eastern Australia means that generalisations drawn from the African and American literature may not hold elsewhere in the biome. The scarcity of multi-service studies limits understanding of trade-offs and synergies, for instance between charcoal production and carbon storage, or between grazing and cultural landscape values. And the modest share of economic valuation studies suggests untapped opportunities for connecting ecological knowledge to the financial and policy instruments that increasingly govern land-use decisions.

More broadly, the study is a reminder that science itself has a geography. An applied field whose stated aim is to elevate the consideration of nature’s services in decision-making would ideally track the characteristics and evolving needs of local populations. The finding that publication patterns decouple from human pressure indicators invites reflection on how research agendas are set, whose priorities they serve, and how funding structures and institutional capacities might be rebalanced so that the regions facing the greatest pressures on their woodlands and savannahs are not left with the thinnest evidence base for managing them.

Subject of Research: Ecosystem service research in the dry subtropics shows strong geographic and thematic imbalances, driven more by institutional and research agendas than by local human pressures.

Article Title: Ecosystem service research in the dry subtropics: Current state, temporal changes and drivers of regional variability

Article References: Aragón, R., & Baldi, G. (2024). Ecosystem service research in the dry subtropics: Current state, temporal changes and drivers of regional variability. One Ecosystem, 9, Article e118444. https://doi.org/10.3897/oneeco.9.e118444

Image Credits: AI Generated

DOI: 10.3897/oneeco.9.e118444

Keywords: ecosystem services, dry subtropics, systematic review, bibliometrics, sustainability science, One Ecosystem, conservation, land use, Ecosystem, service, research, subtropics