Web Extra: Millennium Seed Bank
By Melissa Gaskill
Michael Eason, conservation program coordinator at the Lady
Bird Johnson Wildflower Center, constantly traverses the state, hiking into
remote canyons and up the side of mountains, bouncing down unpaved roads, and
wading through swampy woodlands. The literal fruit of all his labors—thousands
of seeds—fill a deep freeze in a secure room on the Center grounds.
“For me, seed banking is about preserving the natural heritage of Texas,” Eason says. “We’re mostly targeting common plants, not rare ones. But many of the collection sites face threats such as development. We’ve revisited collection sites that are now erased by housing developments or strip malls, so those genetic populations are gone. Other plants, while found throughout an ecoregion, grow only in certain habitats, which makes them uncommon and under threat.” The Wildflower Center is the only organization collecting across Texas, he explains. The majority of collecting takes place on private property, and seven years into the project, the Center enjoys access to a great deal of land.
Successful seed collection depends on a number of factors,
with timing one of the most important. Only mature seeds can be collected, and
a week one way or the other makes a world of difference. Simply finding plants
often presents a major challenge, because some seeds are no larger than a
pencil point, and offer the challenge comparable to that of finding the literal
needle in a multi-acre haystack.
“We may have a list of 1,000 species that occur on a particular property,” Eason says. “But we don’t know exactly where the plants are or whether numbers are sufficient for collecting.” The Nature Conservancy’s Davis Mountains Preserve, for example, encompasses 30,000 acres of rugged mountain terrain, which is largely inaccessible except to hikers. For collecting there, Eason and his staff determine 30 to 50 target species based on what other groups around the country have collected, growing conditions that particular year, and when a plant produces seeds. Last June, collecting on the Preserve focused on one trail up Mount Livermore. Eason and another staff member monitored plants every other week on the property through summer and fall, then in late October, brought in 15 volunteers over one weekend, gathering more than 20,000 seeds for ten species.
Texas weather regularly disrupts collection plans. In one case, Eason slogged through the East Texas landscape for many hours in pouring rain, far from ideal collecting conditions due to the threat of mold. Last fall, Hurricane Ike destroyed many plants targeted for collection. In West Texas, heat can thwart even the most enthusiastic collectors.
Depending on the species, collectors pick individual seeds, ripe fruit, or pine cones, holding them in paper or cloth bags. They record GPS coordinates, other species growing in association with the plant, date of collection, geology and other data. Back at the Wildflower Center, dozens of volunteers assemble for five or six hours to clean seeds, which are then packed in aluminum envelopes. These are labeled and heat sealed before going into the freezer.
The Millennium Seed Bank Project at the Royal Botanic Gardens in Kew, England, determined that banking 20,000 seeds per species provides sufficient numbers for conservation in both the U.K. and the U.S., for germination tests, research, and restoration. Of 20,000 seeds collected, usually 7,000 remain at the Wildflower Center—with most species, enough to fill about a quarter of a cup. Another 3,000 end up at the National Center for Genetic Resources Preservation’s seed bank in Fort Collins, Colorado. The other 10,000 go to Kew, joining seeds from nearly 500 different Texas plant species residing in underground freezers. The Bank’s total deposits represent roughly 10 percent of the world’s upland flora species, or more than a billion seeds from some 19,000 species, says Flo Oxley, director of conservation for the Wildflower Center. And Eason and his colleagues continue to search for more.
From the June 2012 issue.