A comprehensive study of the world's plant species has led researchers to a troubling conclusion: In the tropics, sometime in the next 50 years, it will likely get too hot for seeds to germinate.
That's according to a team from the University of New South Wales (UNSW) in Australia, led by Alexander T. Sentinella of the Sydney-based Center for Ecology and Evolution Research. Their work was recently published in the journal Global Ecology and Biogeography.
The researchers based their findings on an analysis of more than 1,300 plant species, none of them agricultural, maintained in a global seed germination database maintained by Kew Royal Botanic Gardens in the UK.
Sentinella and her team reviewed nearly 10,000 Kew records to better understand the impact of rising temperatures, looking at plant life on every continent except Antarctica.
"With seeds, you can experiment quickly, there are a lot of studies on them, and more importantly, germination is directly related to how a species will survive, because if the seed doesn't germinate, the plant won't live," he says. Sentinella.
Along with evaluating the seeds, the research team generated temperature projections for the year 2070 to measure the levels at which the seeds will remain viable within that time period.
The Australian team found that tropical plants do not necessarily have lower temperature tolerances for survival than species in other latitudes, as animals have long been thought, but that their greatest risk is pushing against the threshold of temperatures. maximum seed germination.
In fact, the risk to plants increases the closer they are to the Equator, but it is the damage to the seeds that scientists are concerned about.
“These plants could be at higher risk because they are near their upper limits. So even a small increase in temperature due to climate change could push them to the limit, "warns Sentinella. "The numbers are quite shocking because by 2070, more than 20 percent of tropical plant species, we predict, will face temperatures above their upper limit, which means they will not germinate and therefore will not be able to survive."
More than half of tropical species are likely to experience temperatures outside their optimal germination windows. "If a seed's germination rate is 100 percent at its optimum temperature, then it could only handle 50 or 60 percent, for example, if the temperature is higher than ideal," he adds.
Plant species appear to be more likely to germinate within the same temperature range, regardless of latitude, so some plants may benefit if they can adapt to the warmer climate. In fact, the UNSW team predicts that 95 percent of plant species found at a latitude of 45 degrees or more will see changes toward the optimal range for germination.
That being said, Sentinella says that it is difficult to know which plants will survive.
"Some species will not be able to adapt fast enough," he said. “Sometimes the plants can migrate when they start to grow further away from the Equator or, on a mountain side where it is colder. But if a species cannot do it, it will become extinct. "