Stashing seeds in 'Noah's fridge'
Researchers worldwide are collecting seeds from wild plants to guard against the ravages of climate change.
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Plants that define an ecosystem, what scientists call "keystone species," may need help migrating as the global climate changes. If the plains of Illinois are predicted to have the climate of Texas in 100 years, for example, prairie grasses growing there will have to withstand the conditions of present-day Texas, says Pati Vitt, manager of conservation programs at the Chicago Botanical Garden.Skip to next paragraph
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But with both natural and unnatural obstacles between two regions, and the rate of change so rapid, scientists worry that species migration won't happen on its own. So some propose "assisted migration" – aiding vegetation shifts by planting southern species in the north ahead of predicted climatic shifts.
An even more controversial approach involves hybridizing northern species with southern ones to make plants that will be more tolerant of the future climate.
Such proposals raise a host of questions: What should an ecosystem that never existed in a particular place look like? What happens if "assisted" species hurt the plants already there? Whatever the resolutions to these and other questions, without seed banking efforts now, such tactics won't be possible in the future, says Dr. Vitt.
"We maybe have a very narrow window of time where we still have a level of geographic range and diversity and plants that are producing seeds," she says, from a field site near a highway in Illinois. "I can't tell you how narrow that window is.… I don't know. But we do have a sense of urgency."
The ins and outs of seedbanking
Careful drying and storing can reliably hold seeds in suspended animation for at least two centuries. The real challenge is ensuring genetic diversity. Without it, scientists will have a harder time reestablishing viable plant populations in the wild.
At San Diego Zoo's Conservation and Research for Endangered Species, scientists typically collect seeds from at least 100 individual plants of the same species. That's enough, they estimate, to preserve 98 percent of a species' genetic diversity.
The most comprehensive collections include seeds from different years. By gathering seeds from different seasons, scientists know that their seed collections contain any variations that might lead a variety of plant to prefer hot over cold, wet over dry, and vice versa.
While in the field collecting, scientists jot down information on the surroundings. Was the plant in the shade, on a hill, near a stream? Once in the lab, scientists expose some seeds to various combinations of moisture, daylight, and temperature to determine their ideal germinating conditions. All this information goes into a database to help guide future restoration efforts.
The remaining seeds are dried for up to several months. Once desiccated, the seeds go into insulated silver pouches and, eventually, refrigerators where they'll be kept at minus 20 degrees C (minus 4 degrees F.). In these conditions, seeds can last up to 500 years.
In all, "securing a species" costs some £2,000 (almost $4,000), says Michael Way, the Americas coordinator in the seed conservation department of the Kew Royal Botanical Gardens, which houses Britain's Millennium Seed Bank Project.
Collections at the MSBP, which can reach more than 15,000 seeds per species, average about 3,500 seeds. But if the number of seeds dwindles for any reason, the seed bank may replenish it by growing plants in greenhouses. Scientists prefer not to, however. Greenhouse conditions could generate plants that thrive in "unnatural" conditions, traits that might work against the species in the wild.