By the century's end, the world's arid and semi-arid lands may claim more than 40 percent of Earth's surface — a quiet but profound redrawing of the planet's livable geography. Driven by rising temperatures, shifting rainfall, and accelerating evaporation, this expansion threatens the agricultural foundations and water security that billions of people depend upon. Scientists note that plants, responding to elevated CO₂ by using water more efficiently, may offer a partial natural reprieve — though not a rescue. The projection is less a prophecy than a mirror: what humanity does now will determi
Drylands Could Cover 40% of Earth by 2100, Scientists Warn
Dryland expansion threatens agricultural productivity and habitability for populations in affected regions globally.
Plants could slow the expansion, but not stop it entirely
Mark
So we're talking about a third of the planet becoming desert by 2100. That's a massive claim. What's the actual evidence behind the 40 percent figure?
Mimi
It comes from climate modeling—scientists run simulations based on current CO₂ emissions trajectories and what we know about how temperature and rainfall interact. The models show arid and semi-arid zones expanding significantly. It's not a single study; it's a pattern emerging across multiple research groups.
Luke
But here's the thing: models are projections, not predictions. They're only as good as the assumptions built into them. If emissions drop faster than expected, or if adaptation strategies work better than we think, the actual outcome could be quite different.
Mark
You mentioned plants might slow this down. How does that work?
Mimi
When CO₂ levels rise, plants become more efficient at using water. They lose less moisture through their leaves while pulling the same amount of nutrients from the soil. So in theory, vegetation can survive in drier conditions than it could today.
Luke
That's the theory. But we don't know yet how much that effect will actually matter in practice, or whether it will be enough to offset the drying trend. It's a potential brake, not a guarantee.
Mark
Who gets hit hardest by this?
Mimi
Regions that are already semi-arid or that depend heavily on agriculture in vulnerable zones. Parts of Africa, the Middle East, central Asia, Australia. Anywhere that's on the edge of becoming desert.
Luke
And we should be honest: the poorest populations in those regions have the fewest resources to adapt or relocate. This isn't just an environmental story; it's a human one.
Mark
So what's the actual timeline? Is this a gradual shift or does it happen suddenly?
Mimi
Gradual, mostly. We're talking about changes over decades, not overnight. But that doesn't make it less serious—it means we have time to prepare, if we choose to use it.
Der Puls
- Climate models now place more than 40% of Earth's land surface on a trajectory toward arid or semi-arid conditions by 2100 — a shift with no modern precedent in scale.
- Regions currently sustaining crops, pasture, and dense human settlement face a slow-motion transition into landscapes that can support far less of each.
- Rising CO₂ is the engine of the crisis, but it also carries an unexpected moderating force: plants become more water-efficient as concentrations climb, potentially slowing the worst projections.
- Food systems, freshwater access, and the habitability of entire regions hang in the balance, with vulnerable populations facing the hardest choices about migration and land use.
- The 40% figure is not fixed — aggressive emissions reductions could shrink it, while continued inaction could push it higher, leaving the outcome still within human reach but only barely.
By the century's end, the world's arid and semi-arid lands may claim more than 40 percent of Earth's surface — a quiet but profound redrawing of the planet's livable geography. Driven by rising temperatures, shifting rainfall, and accelerating evaporation, this expansion threatens the agricultural foundations and water security that billions of people depend upon. Scientists note that plants, responding to elevated CO₂ by using water more efficiently, may offer a partial natural reprieve — though not a rescue. The projection is less a prophecy than a mirror: what humanity does now will determine how much of the map turns to dust.
Scientists projecting Earth's climate through the end of this century have arrived at a striking and sobering figure: arid and semi-arid regions could cover more than 40 percent of the planet's land surface by 2100. Drylands already account for roughly one-third of global land today — stretching across the Sahara, the Middle East, central Asia, and parts of Australia and the American Southwest. The new modeling suggests that a significant additional portion of land currently used for farming, grazing, and human settlement would cross into arid conditions, fundamentally changing what those landscapes can sustain.
The mechanism is familiar: as CO₂ concentrations rise and temperatures follow, rainfall patterns shift and evaporation intensifies. The drying is not uniform — some regions will feel it far more acutely than others — but the overall direction is clear. Agricultural zones would migrate poleward, water resources would tighten, and ecosystems already adapted to semi-arid stress would face conditions beyond their tolerance.
There is, however, a partial counterweight embedded in the biology of plants themselves. As atmospheric CO₂ rises, vegetation becomes more efficient at extracting moisture from soil, losing less water through its leaves in the process. This CO₂ fertilization effect could act as a natural brake on dryland expansion in some areas — meaningful, but not sufficient to reverse the broader trend.
What the research ultimately makes clear is that the 40 percent figure is not destiny. It reflects a continuation of current emissions trajectories. Meaningful reductions could limit the expansion; accelerating emissions could worsen it. For communities and policymakers in dryland-adjacent regions, the projection is both a warning and an opening — a signal that the choices made in the coming decades will determine how much of the map, and how many lives, the drylands ultimately claim.
A team of scientists has projected that by the end of this century, arid and semi-arid regions—what researchers call drylands—could expand to cover more than 40 percent of Earth's land surface. The finding, drawn from climate modeling studies, represents a dramatic reshaping of the planet's geography and poses significant risks to agriculture, ecosystems, and human populations across multiple continents.
The expansion would represent a substantial shift from current conditions. Today, drylands already cover roughly one-third of the world's land area, concentrated in regions like the Sahara, the Middle East, central Asia, and parts of Australia and the American Southwest. If the projection holds, an additional swath of territory—currently supporting crops, pasture, and human settlement—would transition into arid or semi-arid conditions, fundamentally altering the viability of those landscapes for traditional uses.
The mechanism driving this expansion is well understood: as atmospheric carbon dioxide concentrations rise and global temperatures climb, rainfall patterns shift and evaporation increases. Regions that currently receive enough precipitation to support vegetation and agriculture gradually dry out. The process is not uniform—some areas will experience more dramatic changes than others—but the overall trajectory, according to the modeling, points toward a drier planet by 2100.
Yet the picture is not entirely bleak. Research suggests that plants themselves may offer a partial counterbalance to this trend. As CO₂ levels rise, vegetation responds by becoming more efficient at water use—a phenomenon known as CO₂ fertilization. Plants can extract more moisture from the soil with less water loss through their leaves, which means they require less rainfall to survive and thrive. This physiological adaptation could slow or moderate the pace of dryland expansion in some regions, acting as a natural brake on the most severe projections.
The stakes of this transformation are substantial. Agricultural zones would shift poleward, away from the equator, potentially reducing productive farmland in regions already vulnerable to food insecurity. Ecosystems adapted to semi-arid conditions would face pressure as those conditions intensify. Water resources would become scarcer in areas that depend on them. Populations in affected regions would confront difficult choices about migration, land use, and economic adaptation.
The research underscores a central tension in climate science: the future is not predetermined, but the window for altering its trajectory is narrowing. The 40 percent figure assumes current emissions trends continue. Aggressive reductions in greenhouse gas emissions could limit dryland expansion to smaller percentages. Conversely, if emissions accelerate, the expansion could be even more severe. The role of plant adaptation adds another variable—one that suggests Earth's ecosystems may provide some resilience, but not enough to eliminate the challenge entirely.
For policymakers and communities in dryland-adjacent regions, the projection serves as both warning and call to action. Understanding how quickly and where these transitions will occur remains an active area of research, as does identifying which adaptation strategies—from agricultural innovation to water management to planned migration—might help populations navigate the changes ahead.
Bemerkenswerte Zitate
Plants' ability to respond to elevated CO₂ levels may provide a natural brake on dryland expansion— Research findings cited in climate studies
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