Cacti are often treated as symbols of survival in dry landscapes, but drought tolerance does not make every species immune to a hotter and more variable climate. A Nature study published on November 11, 2026, modelled 993 cactus species and found that including severe drought in climate projections substantially increases the area of suitable climate they could lose by 2100. The results show why biodiversity forecasts based only on long-term average rainfall and temperature can miss the damage caused by extreme events.

Drought tolerance is not the same as drought immunity

Cacti have evolved an extraordinary range of adaptations for living in dry environments. Many store water in fleshy stems, reduce leaf area to limit evaporation, use shallow or extensive root systems to capture brief rainfall and rely on crassulacean acid metabolism, a form of photosynthesis that can reduce water loss. These features help many species survive conditions that would be difficult for less specialised plants. But the cactus family is diverse, and not every species occupies the hottest or driest deserts.

Some cacti grow in seasonally dry forests, grasslands, coastal fog zones and cooler mountain environments. Their ability to withstand short periods of water stress does not mean they can tolerate every combination of prolonged drought, extreme heat and changing rainfall. A plant may survive a dry spell yet fail to flower, set seed or recruit new seedlings. Repeated stress can also weaken populations over time. The new research is important because it tests the assumption that drought-adapted plants will automatically be protected as climate extremes intensify.

A global analysis covering 993 cactus species

The study, published in Nature on November 11, combined a curated dataset of 648,316 cactus occurrence records with spatial projections of severe drought and warming. The researchers used species-distribution models to assess the future area of suitable climatic conditions for 993 species of Cactaceae. The records came from biodiversity databases, field observations and community-science sources, including iNaturalist. The analysis was designed to compare models that include long-term climate averages with models that also account for severe drought.

The scale of the dataset matters because cactus species are unevenly distributed across the Americas and many have relatively small geographic ranges. A study based on a handful of well-known desert plants would miss much of that diversity. The researchers also considered different climate scenarios and dispersal assumptions, which affect how easily a species might reach newly suitable areas. The result is not a census of every individual cactus or a direct count of plants that will die. It is a model-based assessment of how much climatic space could remain suitable under different future conditions.

Extreme drought changes the forecast

Most conventional species-distribution models rely heavily on long-term average temperature and rainfall. Those averages are useful, but they can hide the effect of extreme events. A region may have a climate that appears suitable when averaged over many years, even though it experiences occasional droughts severe enough to kill plants or prevent successful reproduction. By incorporating spatial data on severe drought and the compounding effect of warmer temperatures, the researchers found that models including drought were better supported in 91 per cent of the cases they examined.

Under scenarios that allowed species to disperse up to 100 kilometres, models using long-term climate averages alone projected that 58 to 61 per cent of species would lose suitable climatic area. When severe drought was included, the share rose to 69 to 72 per cent. The difference shows why extreme events matter for ecological forecasting. A species may appear capable of tracking a gradual shift in average climate but still face repeated drought episodes that undermine survival in the places where its range is expected to move.

More species face the prospect of very large range contractions

The study found that the proportion of species projected to lose more than a quarter of their suitable climatic area increased from 26 to 43 per cent in models without severe drought to 55 to 58 per cent when drought was included. The most striking result concerns species projected to lose more than four-fifths of their suitable area. Depending on the emissions scenario, that share rose from 1 to 15 per cent without severe drought to 25 to 35 per cent with severe drought included.

Those figures should be read as ranges across the study’s climate scenarios and modelling choices, not as a single prediction for every cactus. They describe projected changes in suitable climatic area, not a guarantee that a given percentage of plants will die or that a species will become extinct by a specified date. A cactus may persist in a small refuge even after most of its current climatic range becomes less suitable. Conversely, a species with a large range can still suffer serious losses if the remaining suitable areas are fragmented or inaccessible.

Dispersal limits can make the outlook worse

Plants do not move across landscapes in the same way that mobile animals do. Cacti may disperse through seeds carried by wind, water or animals, but successful establishment depends on suitable soil, rainfall timing, pollinators and the presence of safe places for seedlings to grow. The researchers compared a scenario allowing 100 kilometres of dispersal with a scenario that restricted dispersal to zero kilometres. Under the severe-drought models, the share of species losing suitable area rose from 69 to 72 per cent with 100-kilometre dispersal to 84 to 85 per cent when dispersal was restricted.

This difference highlights a practical conservation problem. Even if a new area becomes climatically suitable, a cactus may not reach it naturally. Roads, farms, urban development, fences and fragmented habitat can separate current populations from future refuges. Some species have highly localised ranges or specialised relationships with pollinators and soil conditions. Protecting connected landscapes and maintaining seed sources may therefore be as important as reducing greenhouse-gas emissions. Assisted movement may be considered for some species, but it requires careful assessment of ecological risks and local community priorities.

Regional hotspots could lose a substantial share of cactus diversity

The researchers identified five bioregions where projected losses could reduce regional cactus richness by more than 25 per cent. The IUCN summary highlights cactus diversity hotspots including Chile, Peru and northeastern Brazil as areas where losses could be especially severe. These regions contain species adapted to particular combinations of altitude, rainfall, soil and local climate. When severe drought is added to the projections, some of those specialised environments become less reliable as long-term refuges.

Regional richness matters because ecosystems depend on networks of species, not only on individual plants. A decline in cactus diversity can change the availability of flowers, fruits, nectar and nesting structures. It can also alter the seasonal resources used by insects, birds, bats and mammals. The impact will vary by region and species. A general decline in suitable climate does not mean every local ecosystem will respond in the same way, but it does show why conservation planning should identify vulnerable hotspots rather than treat all desert landscapes as interchangeable.

Cacti support wildlife, livelihoods and cultural traditions

Cacti provide food and shelter for many animals. Flowers can supply nectar and pollen to bats, birds and insects; fruits are eaten by mammals and birds; and the plants themselves can provide nesting sites or protection from predators. In the Sonoran Desert, the senita moth depends on the senita cactus to complete its life cycle. In the Galápagos, cactus finches use endemic prickly pear species for food and nesting habitat. These relationships mean that cactus losses can affect other species even when those animals are not directly exposed to drought.

Cacti also have cultural and economic value. Indigenous communities in the Sonoran Desert, including the Tohono O’odham, harvest saguaro fruits and use them in foods and traditional ceremonies. In parts of Latin America, cactus species are important to local landscapes, tourism, horticulture and traditional knowledge. The consequences of a declining population can therefore extend beyond biodiversity statistics. Conservation measures need to recognise the people who have long cared for these plants and the ways in which local livelihoods, cultural practices and ecological resilience are connected.

Climate change is not the only pressure on cactus populations

The IUCN has reported that more than 30 per cent of cactus species are already threatened with extinction, with habitat destruction and illegal collection among the major pressures. Urban expansion, agriculture, mining, roads and land conversion can remove habitat or divide populations into smaller fragments. Illegal collection is particularly damaging for rare and slow-growing species because removing mature plants can eliminate individuals that took many years to reach reproductive age. Climate change adds another pressure to species that may already be declining.

The new study therefore should not be interpreted as saying that drought alone explains the future of cacti. A population may be threatened by a combination of changing climate, habitat loss, poaching, invasive species and altered fire or grazing regimes. Conservation assessments need to consider those factors together. A species that retains some suitable climatic area may still be at risk if the remaining habitat is destroyed or if illegal collection removes its reproductive individuals. Conversely, protecting habitat and reducing extraction can improve resilience even when the climate outlook is difficult.

How the findings could change Red List assessments

The research provides new evidence for the next round of IUCN Red List assessments of cactus species. The IUCN says that losing 80 per cent of suitable habitat could qualify some species for Critically Endangered status under relevant criteria, potentially more than doubling the number of cacti in that highest threat category. The organisation plans regional expert workshops in the United States, Mexico and South America during 2027 to update assessments and identify priority conservation actions.

An updated Red List does not itself protect a species, but it can influence land-use planning, funding, enforcement and public awareness. A clearer picture of drought exposure can help conservation groups identify refuges, prioritise seed banking, monitor wild populations and support restoration. It can also guide decisions about where to protect habitat corridors or work with landowners. The value of the study is not only that it produces a warning. It offers a consistent evidence base that can help conservation planners decide where limited resources may have the greatest effect.

What the models cannot predict with certainty

Species-distribution models estimate where climate conditions may be suitable; they do not fully capture every ecological interaction or the capacity of a plant to adapt. The study’s occurrence dataset is extensive, but records are uneven across regions and species. Some cactus populations are difficult to survey, and the threat of illegal collection can limit the public release of precise location data. The researchers also had to make assumptions about dispersal, climate scenarios and the relationship between drought exposure and survival.

These uncertainties do not make the results unimportant. They show why projections should be treated as decision-support tools rather than exact forecasts. The strong improvement in model support when severe drought was included suggests that average climate alone can miss a meaningful part of the risk. Future work can combine long-term field monitoring, seedling survival studies, physiological experiments and better drought projections to test the models. The most useful response is to act on the direction of the evidence while continuing to refine the estimates.

The larger lesson for biodiversity forecasting

The study’s central message extends beyond cacti. Many species have adaptations that help them survive typical conditions but leave them vulnerable to extremes. Forest trees may tolerate seasonal dry periods yet fail during prolonged heatwaves. Amphibians may depend on temporary pools that disappear during severe drought. Alpine plants can face both warming and reduced snow cover. If models focus only on long-term averages, they may underestimate the pressure created by rare but damaging events.

Conservation planning is increasingly concerned with compound extremes: heat combined with drought, drought followed by wildfire, or heavy rainfall followed by erosion. The cactus research provides a clear example of how adding those events can change the outlook for an entire plant family. It does not mean every cactus is doomed. It means that resilience has limits, and that the future of drought-adapted species depends on both climate action and practical protection of the landscapes where they live.