Climate change set to drive tens of thousands of plant species extinct by century's end

Full article

Two studies published Thursday in the journal Science paint a stark picture of the future of the world’s plants, warning that climate change is set to drive tens of thousands of species extinct and that thousands of evolutionarily unique flowering plants are already at risk of disappearing.

A global analysis led by Xiaoli Dong, an ecologist at the University of California, Davis, used millions of biology and climate computer simulations to examine the future of 18% of the world’s plant species in detail. The findings, the researchers said, offer a reliable window into what is in store for all plant life.

Under moderate scenarios for carbon pollution, between 7% and 16% of the world’s plant species are likely to lose at least 90% of their habitat and go essentially extinct in the next 55 to 75 years, the study found. That translates to roughly 35,000 to 50,000 species, and the number will climb higher if emissions rise further, Dong said.

“The warming rate drives the extinction,” Dong said.

Scientists have long expected that plant species could gradually shift to cooler climates as the world warms, carried toward the poles or higher altitudes by wind, water, and animals. Researchers have observed this process in the field and even relocated plants to conserve them. But Dong’s millions of simulations showed that even if species move as quickly as possible, the extinction rate will not drop.

“It is not because they are not moving fast enough,” Dong said — it is because the specific habitats that plants depend on will no longer exist.

Climate change, whether through rising temperatures or shifting rainfall patterns, will make areas where plants once grew no longer livable for some species, she explained. Dong used the example of a tulip, which requires a specific combination of soil, temperature, and rain. Climate change is pulling these elements apart: the right temperature pushes north, the proper rain pattern moves east, and the soil remains where it was. “The perfect condition required by this tulip has become like really small,” she said.

The study found that the situation is becoming especially severe in the Arctic, where temperatures are rising four times faster than the global average, and in the Mediterranean and Australia, where rainfall changes are the primary driver.

A second study published in the same issue of Science examined the current extinction risk facing flowering plants, a group with more than 335,000 species. Scientists at Kew Gardens in the United Kingdom found that nearly 10,000 flowering plant species are now in danger of vanishing. These species are so evolutionarily old and unusual that their loss would erase 21% of Earth’s “tree of life,” the researchers said.

The threatened species include oddities such as the titan arum, the world’s smelliest plant, and species with direct human use, such as the orchid that produces vanilla.

Lead author Felix Forest, an evolutionary plant biologist at Kew Gardens, applied a 20-year system that British biologists developed to prioritize species conservation by focusing on the most unique species. The study does not examine what is driving the extinction risk but instead documents what would be lost in terms of biological history and distinctiveness.

In what the scientists described as the largest species prioritization study ever undertaken, Forest found that more evolutionary history is at risk in unusual flowering plants than in almost any other group of flora or fauna, with only turtles and tortoises carrying more.

Some species, such as certain types of rats, have close relatives and bushy branches on the tree of life, Forest said. If one species disappears, others remain to share its evolutionary history. But flowering plants include species like the Ginkgo biloba, which has no similar relatives and represents hundreds of millions of years of unique evolution.

Both Dong and Forest said that plant extinction is regularly overlooked, even by official organizations, when compared with the attention paid to animals.

“We’re trying to redress that imbalance between plants and animals, especially vertebrates,” Forest said. “Humans are generally more interested in fluffy furry things and things with two wings than plants. And that’s just the way things are.”

Chilean biologists Rosa Scherson and Federico Luebert, who were not involved in either study, wrote in a review accompanying the research that the two studies together show that the world cannot wait to act.

When the future of plants is unstable, “it can also affect human food security and access to basic materials,” Scherson and Luebert wrote. “Maintaining the current conditions that support human life requires urgent action.”