even cacti can’t stand the heat

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Paris (AFP)- Sixty percent of cacti species will end up in less hospitable climates over the next few decades as global warming takes hold, according to new research challenging the long-held assumption that iconic desert plants will thrive with more heat.

By 2070, up to 90% could be at risk of extinction due to climate change, habitat loss and other stressors, triple the current percentage, scientists report in Nature Plants. .

Some 1,500 species of cacti distributed across the Americas live in a variety of climates, ranging from sea-level deserts to the high mountains of the Andes, from arid ecosystems to tropical rainforests.

Biodiversity hotspots rich in species and numbers include central Mexico and the Brazilian Atlantic Forest.

To test the idea that cacti will benefit from a warmer, more drought-prone world, researchers led by Michiel Pillet at the University of Arizona looked at data on more than 400 species and ran models projecting how they would behave mid-century and beyond under different greenhouse gas emissions scenarios.

The results “paint a more pessimistic future”, according to the study published Thursday.

Currently, the main threat to cacti is the expansion of agriculture, along with land degradation, loss of biodiversity and harvesting for various purposes.

Even without climate change, cacti “are one of the most threatened groups of organisms on the planet”, with more than 30% of them classified as threatened with extinction, the authors note.

In a moderate emissions scenario consistent with current policies, global warming will soon also pose a significant threat.

“Our results suggest that climate change will become one of the main drivers of cacti extinction risk, with 60-90% of species assessed to be negatively impacted” by global warming, the researchers reported.

Within four or five decades, some 25% of cactus species could experience unknown climates across a quarter of their current range.

Previous studies have shown impaired photosynthesis – the process by which plants use sunlight to make food from CO2 and water – with just two degrees Celsius of global warming.

The average surface temperature of the Earth, including the oceans, is already 1.1 C warmer than in pre-industrial times and about 1.7 C above the land alone.

Teresa H. Sadler