The central insight of the study is that plant diversity functions as a form of ecological insurance. Climate change is expected to reduce the productivity of the plant species that currently dominate pastures and meadows, but a diverse plant community contains species with a wide range of traits, including some that tolerate heat, drought, or shifting growing seasons far better than others. When diversity is preserved, those resilient species have the opportunity to become more prominent as conditions change, cushioning the overall decline in carbon uptake. When diversity is lost, that buffer disappears, and the ecosystem’s productivity falls with it.

“Climate change could reduce the productivity of plants that at the moment dominate pastures and meadows. But if plant diversity is maintained, other plants that cope better with climate impacts have the chance to become more prominent and stem the decline,” explained Stephen Wirth, PIK researcher and lead author of the study. His framing captures the mechanism at the heart of the research: functional diversity is not merely an aesthetic feature of a healthy meadow but a dynamic portfolio of traits that allows the ecosystem to reorganize itself under stress.

The stakes extend well beyond the carbon cycle. “It’s not just about the lower rates of photosynthesis, but losing plant diversity also reduces forage supply for grazing animals, which in turn can threaten the livelihoods of people who depend on livestock grazing. Soils also store less carbon and contribute less to limiting global warming,” Wirth added. Grasslands cover roughly forty percent of Earth’s land surface and support hundreds of millions of pastoralists and farmers, particularly across Africa, Central Asia, and South America. A decline in forage availability therefore translates directly into economic and food-security risk, while reduced soil carbon storage creates a feedback loop in which ecosystem degradation accelerates the very warming that caused it.

Scientifically, the study builds on a well-established experimental literature. For decades, small-scale field experiments, most famously the long-running biodiversity manipulations in European and American grasslands, have demonstrated that plots with more plant species tend to be more productive, more stable through time, and better at storing carbon in soils. What those experiments could not deliver was a global picture: how would the loss of diversity interact with rising temperatures and shifting precipitation across every grassland biome on the planet? To answer that question, the research team turned to a global vegetation model, a computational framework that simulates plant growth, photosynthesis, water and nutrient cycling, and soil carbon dynamics across the entire land surface under specified climate conditions.

The researchers used the model to compare two futures for the world’s grasslands: one in which plant diversity is maintained and one in which it is strongly reduced. To probe the potential consequences of diversity loss, they deliberately assumed an extreme loss of plant diversity in the model, a worst-case scenario designed to reveal the upper bounds of the damage. They then ran the simulations under two climate scenarios, one in which global warming remains below 2°C relative to pre-industrial levels and another in which warming reaches approximately 4°C. This design allowed the team to separate the effects of diversity loss from the effects of warming itself, and to test whether the insurance value of diversity holds even in a comparatively mild climate future.

The numbers that emerged are striking. Under 2°C of warming, grasslands with strongly reduced diversity take up around 11 billion tonnes less CO₂ per year through photosynthesis in 2050 than grasslands where diversity is maintained. To put that figure in perspective, the researchers note that this reduction in uptake would be comparable to losing an area of grassland with average productivity roughly the size of the Arctic tundra, an entire biome’s worth of carbon-absorbing capacity erased not by land conversion but by the quiet erosion of species richness. The model also projects lower soil carbon stocks wherever diversity is reduced, meaning the damage compounds over time as less organic matter is returned to the ground and stabilized.

The geographic pattern of the losses is equally revealing. Particularly large differences in CO₂ uptake in 2050 are evident across many tropical and subtropical regions, where grasslands with strongly reduced diversity take up as much as 50 percent less CO₂ than those where diversity is preserved. The extent to which grasslands benefit from diversity varies considerably from region to region, reflecting differences in climate trajectories, soil conditions, and the functional traits of local floras. “In some regions, remaining plants can compensate for the loss of other plant types, and productivity may even increase. Globally, however, the benefits of maintaining diversity prevail in both climate scenarios,” commented Susanne Rolinski, PIK researcher and co-author of the study. That regional nuance matters: in a handful of places, the survivors of a depauperate community may thrive as competitors disappear, but averaged across the planet, the insurance value of diversity wins out decisively.

The researchers are careful to acknowledge the limits of their approach. The exact magnitude of these effects remains uncertain because the model simplifies plant traits and the intricate interactions among species, soils, microbes, and climate. Real grasslands are shaped by grazing pressure, fire, land management, and evolutionary adaptation, none of which can be captured perfectly in a global simulation. Yet the direction of the finding aligns with decades of experimental evidence, and the scale of the projected losses suggests that even if the true numbers were considerably smaller, the consequences for the global carbon budget and for pastoral livelihoods would still be profound. The study, published under the title describing how global grassland productivity and carbon storage benefit from functional diversity under climate change, carries the DOI 10.1073/pnas.2528067123.

The policy implications are already taking shape. “To maintain grassland productivity under climate change, we need management practices that preserve existing diversity over the long term and prevent overgrazing,” said Friedhelm Taube, researcher at Kiel University and co-author of the study. Overgrazing is one of the principal drivers of plant diversity loss worldwide, selectively eliminating palatable species and pushing rangelands toward degradation. “Agricultural policy should support farmers in adapting their farms to climate change accordingly. This can help strengthen the livelihoods of people who depend on livestock grazing, particularly in the Global South,” Taube concluded. In practice, that could mean rotational grazing schemes, seed mixtures that restore functional diversity, payment schemes that reward farmers for carbon storage and biodiversity, and agricultural subsidies redirected toward resilience rather than raw output. As the study makes clear, the choice facing the world’s grasslands is not simply between a diverse future and a poorer one; it is between an ecosystem that can adapt and one that cannot. The 15 percent figure is a global average, but behind it lies a simple biological truth: the more cards a meadow holds, the better its odds in a rapidly changing climate.

Subject of Research: The impact of plant diversity loss on global grassland carbon uptake and soil carbon storage under climate change

Article Title: Plant diversity as insurance against climate change: Loss of diversity in grasslands could lead to 15 percent less CO₂ uptake in 2050

Article References: Plant diversity as insurance against climate change: Loss of diversity in grasslands could lead to 15 percent less CO₂ uptake in 2050. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: plant diversity, grasslands, carbon uptake, photosynthesis, climate change, soil carbon, global vegetation model, biodiversity, pastoral livelihoods, overgrazing, PNAS, Potsdam Institute