Botanic gardens around the world are failing to conserve the rarest and most threatened species growing in their living collections because they are running out of space, according to research from the University of Cambridge.
Researchers analysed a century’s worth of records from 50 botanic gardens and arboreta, collectively growing half-a-million plants, to see how the world’s living plant collections have changed since 1921.
The results, published in the journal Nature Ecology & Evolution, suggest the world’s living collections have reached peak capacity, while international restrictions on plant collecting are impeding efforts to study and preserve global plant diversity.
Cambridge University Botanic Garden curator Prof Sam Brockington, who led the research, said: “Botanic gardens are full. We’re running out of space and resources. The rate at which plants are being listed as threatened is increasing much more rapidly than the rate at which we’re managing to respond. The risk of extinction is accelerating and our response is too slow.”
In 2020, research by the Royal Botanic Gardens at Kew found that 40% of the world’s plant species are at risk of extinction as a result of the destruction of the natural world.
Now, botanic gardens around the world are struggling to find the space to conserve rare plants and save endangered species. “They can’t all fit,” said Brockington. Cambridge University Botanic Garden, for example, is home to more than 8,000 species. “That’s more than a tropical country like Vietnam, growing in a tiny little acreage of Cambridge.”
Despite this, to help conserve the world’s biodiversity, the garden added half-a-million seeds from rare or threatened wild plants to its collection last year and acquired numerous critically endangered plants from other botanic gardens. This included the Tahina spectabilis, a palm that can grow up to 18m tall, and the Pinus torreyana, one of the rarest pine trees.
Threatened plants such as these must compete for space in botanic gardens with beautiful, famous – but less endangered – flowers, trees and landscapes that will attract visitors and inspire people to learn about gardening and the natural world.
“We’re also trying to grow plants for scientific collections, so they’ve got to be useful for science and they’re also used for learning programmes,” Brockington said. “So even though botanic gardens are collectively at peak capacity, we’re only probably devoting about 5-10% of that capacity to this question of conservation.”
Brockington said one solution to create more capacity could be to build more botanic gardens in the global south. “The global distribution of botanic gardens doesn’t match – and never has matched – where all of the important biodiversity is.”
The first botanic gardens were founded during the colonial era, and almost all are located in the west. In the past, botanists from these gardens would engage in “extractive, colonial-type practices”, visiting poorer nations to “pull out whatever plants they or their rich patrons were interested in, bring them back and cultivate them,” Brockington said.
In 1993, a United Nations Convention on Biological Diversity attempted to stop this by assigning sovereignty over biodiversity to national governments, enabling states to “own” the genetic material within their geopolitical boundaries.
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But the Cambridge University research indicates this is hampering efforts by botanic gardens to collect endangered plants in the wild, and exchange seeds and plant material to protect threatened species from extinction.
To maintain diversity and preserve the world’s living collections, plants must be regularly replaced or propagated. But since the convention was introduced in 1993, the number of plants in botanic gardens collected from the wild has halved, the research found.
“Political boundaries do not help us share material and collectively steward the world’s most threatened biodiversity,” Brockington said.
Brexit, for example, has been “catastrophic” for exchanges of plant material between European botanic gardens, he said. “The bureaucracy of seed exchange can be so costly now, it would be cheaper for our staff to personally fly to somewhere like Sweden, with a legal amount of seed, than send it by post.”
The climate emergency is also threatening the living collections of botanic gardens. Botanic gardens are being forced to focus on plants that will survive the transition to a new climate in decades to come.
Brockington wants the world’s botanic gardens to collaborate to safeguard plant populations by creating one big “meta collection”, where individual specimens of an endangered wild species are extensively cultivated in multiple institutions.
“The ramifications of not acting are that we will lose far more species to extinction than we would otherwise. Maintaining plant diversity could lead to groundbreaking discoveries about food, medicine or materials in the future,” Brockington said. “My fear is that we could lose that diversity before we understand its value to human society.”
English (US)