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Botanical conservatories take on urgent new role

Speed of climate change makes glasshouses bulwarks in the battle to preserve biodiversity.

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Mediterranean Garden: Longwood Gardens in Kennett Square, Pa., now displays more cold-tolerant plants, such as these, that save on heating.

Courtesy of L. Albee/Longwood Gardens

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Conservatories, once the glass-walled playgrounds of wealthy plant collectors, now serve a more urgent function. The changing global climate has spotlighted the role these specialized greenhouses play in preserving plant diversity.

Like zoos for endangered animals, climate-controlled conservatories may well be the only places some plants can survive, allowing scientists to educate the public, including gardeners, about the environmental threats to many species.

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Glasshouses, as they are also known, are often the first stop on visitors' tours of public botanic gardens. These structures hint at the research going on behind the scenes, such as the development of seed banks and collections of endangered plants. Conservatories also cost a good deal to operate, and so they stand at the forefront of efforts to use fuel more efficiently.

Kayri Havens, director of plant science and conservation at the Chicago Botanic Garden, says that scientists began viewing species conservation as a primary function of conservatories only about 50 years ago, when they recognized that such threats as habitat destruction, pollution, even overcollecting were endangering plants around the world.

Dr. Havens is among the scientists at botanical gardens who call climate change "an imminent threat to biodiversity." A decade ago, she says, botanists didn't see it as an urgent problem. Today, "Most of my colleagues and I think that we need to complete a concerted seed-bank effort within a decade – two, at most – to capture species while there still is genetic diversity," she says.

The urgency arises from the varying rates at which plant species reproduce, which determines how quickly they can adapt. "We're particularly worried about species such as trees, which take a long time to reproduce," Havens says.

Memo to Noah: Two is not enough

"The prevailing wisdom is that it's better to conserve seeds, when possible, than living plants in a glasshouse," says Havens, because living plants can become genetically impoverished due to inbreeding, succumb to disease, or fail to grow in a greenhouse. "In order to build a conservation collection" – as opposed to a display collection – "it's necessary to have big numbers to capture genetic diversity. A couple of oaks from Russia doesn't make for a conservation collection, but 1,500-plus seeds in a bank does."

As the US coordinator for native seed banking, Havens heads a team that will contribute 30 million seeds, including 1,500 kinds of endangered native tall-grass prairie seeds, to the international Millennium Seed Bank Project and to a similar national project, Seeds of Success. She notes that dried, frozen seeds in airtight envelopes can stay viable for 200 years.

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Jan Salick, senior curator of ethno­botany at the Missouri Botanical Garden, studies how Tibetan people use high-alpine plants on the eastern edge of the Himalayas, where temperatures are rising quickly. The region is experiencing the fastest glacial retreats in the world and dramatic increases in rainfall. High-alpine meadows, rich in biodiversity, contain rare plants. Dr. Salick's field research shows that as temperatures climb, so do plants – they migrate uphill. The ones migrating fastest are not those endemic to the region, but widespread species that reproduce quickly, outcompeting slower-maturing alpine plants.

The snow lotus, for example, which Tibetans regard as an important medicinal plant, takes 10 years to reproduce and must be pollinated by high-alpine bumblebees. Salick has watched this plant diminish in both size and numbers. "Not until after the fact do you get to see the effect of changes in plant communities on such things as the bumblebees and other long-coevolved, intricate relationships with animal species," she says.

Making 'greener' greenhouses

As the climate changes, Salick and others foresee changes in the form and content of conservatories. Tomasz Anisko, curator of plants at Longwood Gardens in Kennett Square, Pa., says the institution, which focuses primarily on horticultural display, renovated its east conservatory in 2006, in part to improve energy efficiency. With each renovation of Longwood's 1920s-era buildings, the heating systems have been updated to heat soil at the root zone and concentrate hot air immediately around the plants, instead of heating the whole space.

Energy use has also in­­fluenced which spe­­cies to display. "In the past, we ex­­hibited mainly exotic tropical plants that required high temperatures, and we've been replacing them with subtropical and Med­iter­ran­ean plants that can grow in more moderate temperatures," Anisko says, and visitors approve. "That's an important point: You can still design attractive displays and achieve energy savings."

Educating visitors is something Anisko and others believe is a significant opportunity for conservatories. "People don't come to see seeds in the freezer, but to see beautiful plants," Havens observes.

Salick recalls the success story of educating people about the destruction of tropical rain forests. "Public awareness of that issue is amazing," she says. "Kindergartners will ask me about it."

Todd Forrest, vice president for horticulture and living collections at the New York Botanical Garden, says they are targeting average gardeners through an educational program called Gardening in a Changing Climate. "It's important to keep people gardening and give them hope," he says. "Gardens and green spaces are part of the solution to climate change. They provide cool spots, and they store carbon. The more of these we have, the better off our environment will be."