Ecosystems do not fail because of any single threat. They fail because threats accumulate. An international study published in Nature Geoscience in August 2024, led by the Institute of Natural Resources and Agrobiology of Seville (IRNAS-CSIC) of the Spanish National Research Council, found that the resistance of terrestrial ecosystems to global change decreases significantly as the number of environmental stressors increases — especially when that stress is sustained over time. In other words, the combined impact of multiple stressors is greater than the sum of their individual effects, and the natural functions ecosystems provide, from carbon sequestration to soil fertility, weaken disproportionately as pressures multiply.
The Compounding Threat to Ecosystem Resistance
The study's central finding reframes how we should think about environmental decline. For years, much research has examined one stressor at a time — a drought here, a warming trend there. But real ecosystems rarely face threats in isolation. When researchers analyzed how ecosystems respond to multiple global change factors simultaneously, they found that ecosystems become more and more sensitive as the number of factors rises, reducing their natural capacity to resist the impacts of environmental perturbations.
This sensitivity is not additive. According to the study's results, reported by the Spanish National Research Council, the weakening of resistance is disproportionate: two stressors together do more damage than the sum of their separate effects would suggest. The finding is especially pronounced when stress persists over long periods, meaning that ecosystems under chronic, layered pressure are the most vulnerable to being pushed past the point where they can continue functioning.
Understanding Environmental Stressors
The study examined what researchers call global change factors — the human-driven forces that degrade land and destabilize ecosystems. The evidence names drought and overgrazing as factors that can lead to degraded land, and fires as a degradation factor that, when applied over longer periods, affects an ecosystem's ability to provide its services. These stressors rarely arrive alone. A grassland may simultaneously face prolonged drought, recurring fire, and heavy grazing pressure; each one compounds the others' effects.
What makes this combination so damaging is that ecosystems have a finite capacity to absorb disturbance. A healthy ecosystem can buffer a single shock — a dry year, a localized fire — and recover. But when several stressors act at once and persist, that buffering capacity erodes. The study's conclusion, in the words of its researcher Guiyao Zhou, is that "the sustainability of our ecosystems depends on reducing the number of global drivers of change associated with human activity."
The Compounding Effect on Ecosystem Resistance
The framework below synthesizes the study's findings with United Nations context to show how accumulating stressors translate into weakened resistance, degraded services, and tangible consequences. Read it as a chain: each stressor added to an ecosystem reduces its resistance disproportionately, and that lost resistance shows up as failing services and, ultimately, as biodiversity loss and ecosystem transformation.
| Stage | What Happens | Evidence Basis |
|---|---|---|
| Stressors accumulate | Terrestrial ecosystems face multiple simultaneous global change factors, including drought, fires, and overgrazing. | 2024 Nature Geoscience study |
| Resistance weakens disproportionately | As the number of stressors increases, ecosystems become more sensitive, and their resistance to global change decreases significantly — the combined impact exceeds the sum of individual effects, especially under sustained stress. | 2024 Nature Geoscience study |
| Services degrade | Carbon sequestration, important for mitigating climate change, and soil fertility, important for food production, are among the ecosystem services affected; the analysis covered seven services in total. | 2024 Nature Geoscience study |
| Consequences follow | Biodiversity — described by the United Nations as our strongest natural defense against climate change — is lost at an alarming rate, extinction risk rises with every degree of warming, and vital ecosystems face irreversible loss. | United Nations |
The key insight this framework delivers is non-linearity. If stressors merely added up, halving the number of threats would halve the damage. Because their effect compounds instead, reducing the count of stressors matters far more than managing any single one in isolation.
Ecosystem Services Under Threat
"Resistance" can sound abstract, so it helps to anchor it in what ecosystems actually do for us. The study's analysis covered seven ecosystem services, and the researchers highlighted two with global stakes. Carbon sequestration — the ability of plants and soils to absorb and store greenhouse gases — is essential for mitigating climate change. Soil fertility underpins food production. Both depend on ecosystems remaining functional enough to absorb disturbance without tipping into degradation.
When drought, fire, and overgrazing act together over long periods, these services degrade together. That creates a feedback loop with real consequences: an ecosystem that sequesters less carbon contributes to further warming, which in turn intensifies the very stressors that weakened it in the first place.
The Critical Role of Biodiversity and Carbon Sinks
The United Nations frames biodiversity — the variety of life on Earth, from genes and bacteria to entire ecosystems such as forests or coral reefs — as our strongest natural defense against climate change. The Earth's land and ocean serve as natural carbon sinks, absorbing large amounts of greenhouse gas emissions, and conserving and restoring natural spaces is essential for limiting emissions and adapting to climate impacts.
This is why the compounding-stressor finding matters beyond ecology. The main driver of biodiversity loss remains humans' use of land, primarily for food production; human activity has already altered over 70 per cent of all ice-free land. But climate change is playing an increasingly important role, and the UN identifies climate change, biodiversity loss, and pollution as interlinked elements of a triple planetary crisis. Weakened ecosystem resistance accelerates all three at once.
Consequences: Species Extinction and Ecosystem Transformation
The end state of compounding stress is visible in the transformations already underway. According to the United Nations, climate change has altered marine, terrestrial, and freshwater ecosystems around the world, causing the loss of local species, increased diseases, and mass mortality of plants and animals — resulting in the first climate-driven extinctions. On land, increased temperatures compel species to migrate towards higher elevations or latitudes, often moving towards the poles, which has significant impacts on ecosystems. The likelihood of species extinction rises with each degree of global warming. Within marine environments, elevated temperatures heighten the danger of permanent damage to marine and coastal ecosystems. For example, between 2009 and 2018, 14 percent of the world's coral reefs were lost, primarily due to climate change, and continued warming poses a threat to nearly all remaining reefs. These are the measurable outcomes of resistance eroding under layered, sustained pressure.
Monitoring Ecosystem Fragility
The practical decision this evidence points toward is recognizing that the accumulation of diverse environmental stressors disproportionately reduces ecosystem resistance, which necessitates integrated approaches to conservation and climate action rather than single-threat management. The measurable indicators to watch are the observed rate of biodiversity loss and the functional capacity of natural carbon sinks — the two gauges that reveal whether ecosystems are holding their ground or sliding toward transformation. The 2024 study's own conclusion points the same way: sustainability depends on reducing the number of global drivers of change associated with human activity, not merely softening each one.
