Botanical conservatories take on urgent new role
Speed of climate change makes glasshouses bulwarks in the battle to preserve biodiversity.
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
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.
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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How gardeners adjust to a changing climate
“Climatologists tell us that climate change is not as simple as just getting warmer weather,” says Todd Forrest, vice president for horticulture and living collections at the New York Botanical Garden. “They predict that it will become warmer year-round, significantly so in winter, but there will also be great variety in precipitation, increased drought, and more frequent extreme precipitation events. This means we have to take a broad approach to keeping gardens healthy.”
While it is relatively easy to avoid pesticides, gardeners may have a harder time figuring out how to reduce gardening practices that contribute to climate change – and perhaps more worrisome, how climate change is affecting their gardens. Mr. Forrest, who has launched an educational program called Gardening in a Changing Climate, offers guidance in the face of climbing temperatures and “weather weirding” – sudden, often violent, shifts in temperature, wind, and precipitation.
Much of what horticulturists at the New York Botanical Garden have learned from these ventures runs true to the good-gardening practices that have been evolving since the first Earth Day in 1970: “We teach people how to use fuels more efficiently, to choose plants adapted to the local climate, that are drought-tolerant, that aren’t prone to insects and diseases,” he says. “It’s also important to design gardens that take advantage of the natural topography, instead of fighting it.” Rain gardens, for instance, can store water collected on site for use in a later drought.
Unpredictable snowfall, combined with sudden drops in temperature, can mean uncovered plants damaged from freezing, sunburn, and windburn more often than in the past. “We may need to bundle up more of our shrubs in burlap,” he says, to make up for the lack of insulating blankets of snow.
At the New York Botanical Garden, Forrest says, “We are removing pavement where we can and looking at permeable pavements and the overall impact of what we do. It’s not just about temperature, but about the whole landscape.”
Forrest’s most comforting guidance relates to “gardening as a spiritual act” during a confusing and distressing age: “Gardening keeps people in touch with nature. Some say we’ve always been learning to adapt to changing weather, and we can teach others to do the same thing. Good gardening practices are good for the environment. At first blush, everything we do – whether drive or use electric lights – is part of the problem. But gardens are part of the solution. So we should garden wisely by being as efficient as we can, but we should never feel bad about gardening.”
For more information, visit www.nybg.org.
