Scientists discover about 2,000 new plant species every year, but these days, they’re in a race against time.
Plants that have grown on Earth for millions of years are vanishing, due to habitat destruction, climate change and other threats. About 40% of the world’s plant species are at risk of extinction, according to a recent international report.
Botanical gardens, long a bulwark of conservation efforts, are growing more threatened plants to stave off extinction. New research from the Missouri Botanical Garden predicts which plants can survive outdoors in St. Louis — a project intended to help other institutions select species suited to their own climates.
More than 32,000 plants are grown outdoors at the Missouri Botanical Garden, from trumpet-shaped foxglove to towering gingko trees.
Though many of these plants are common, scientists also tend to small populations of extremely rare species grown from seeds, stems and other material collected worldwide. At its core, the goal is to ensure these species continue to exist, says MoBot plant recorder and botanist Georgia Thomas.
Preserving the species outside of its home range “is really important if a plant is so threatened that we can’t save it there or prevent its extinction,” Thomas said. Eventually, she said, scientists can “put that plant back in its native environment, when the threats are less.”
Botanists from the Missouri Botanical Garden have been working with researchers in Kyrgyzstan, for instance, to conserve wild fruit trees. The team hiked through the rugged terrain of the Tian Shan mountains during several field excursions, collecting seeds from rare trees that are the direct ancestors of fruits grown in the U.S. today.
While it’s often easier to grow rare plants in glasshouses, where the climate can be carefully controlled, it’s also much more expensive. Figuring out how to grow these species outdoors, where space is usually more abundant, may help botanical gardens expand the number of species they’re able to conserve, Thomas said.
“The last thing we want to do is to bring in a plant of conservation concern and then realize [because of] our climate in St. Louis, our horticulturists just can’t keep this plant alive,” she said.
Using data from more than 400 species collected from wild populations around the world and grown outdoors at MoBot, Thomas and her colleagues were able to predict how the climate in St. Louis affected their survival. The data included the number of days each plant survived in the garden and if it died, the cause of death, plus a range of climate data collected in St. Louis and the plant’s native habitat.
Some plant species did much better than others, the study found.
Certain species, especially woody shrubs and trees, were much more likely to survive outdoors if they came from nontropical areas, including Europe, Asia, Australia and the southern tip of South America.
Survival was also closely tied to the climate where a plant was collected, which suggests “local adaptation in many plants is really important,” said MoBot scientist and study co-author Ivan Jimenez.
“Rather than thinking about these collections as representing a species, it might be better to think of them as representing populations of species,” Jimenez said.
Given how important climate is to the survival of these rare and threatened plants, the results suggest the Missouri Botanical Garden may have to adjust which species they include in their living collections in the future.
But beyond this specific institution, the team hopes the approach they’ve created can be useful for horticulturists at other botanical gardens.
Because their mathematical models rely on basic information that botanical garden staff typically collect, Thomas said, they could be tailored to help other institutions determine which threatened species could survive in their climates.
“It’s fascinating that we could take these data that we use every day for management of the grounds and use it to inform our collections into the future,” she said. “We really want to work with a network of botanical gardens across the globe to better preserve plants and do this work.”
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