A Hunt for Seeds to Save Species, Perhaps by Helping Them Move

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Pitcher’s thistle, whose fuzzy leaves and creamy pink puffs once thrived in the sand dunes along several of the Great Lakes, was driven by development, drought and weevils into virtual extinction from the shores of Lake Michigan decades ago.

But in the 1990s, seeds collected from different parts of the thistle’s range were grown at the Chicago Botanic Garden and planted with the help of the Morton Arboretum along the lake, in Illinois State Beach Park, north of Chicago near the Wisconsin state line. The plants from Indiana’s dunes to the south are doing well; the plants that had come from the north are failing.

With those mixed results in mind, scientists from the botanic garden are sending teams out across the Midwest and West to the Rocky Mountains and Great Basin to collect seeds from different populations of 1,500 prairie species by 2010, and from 3,000 species by 2020. The goal is to preserve the species and, depending on changes in climate, perhaps even help species that generally grow near one another to migrate to a new range.

“In 50 to 100 years, because habitats or climates are so altered, we might end up trying to move species in a restoration context, in assemblages of species,” said Pati Vitt, a conservation scientist and curator of the Dixon National Tallgrass Prairie Seed Bank at the botanic garden.

The garden is seeking permits to test the concept with the thistle, by pushing it into new, colder territory along the shores of Lake Ontario. “It may be the best test case for moving an individual species outside its range,” Dr. Vitt said.

But assisted migration, as it is called, is a hotly debated issue. On one side are those like the botanic garden scientists, who argue that the risks are better than doing nothing.

“We recognize that climate change is likely to be very rapid and that seeds only disperse a few hundred yards, half a mile at most, naturally,” said Kayri Havens, the botanic garden’s director of plant science and conservation. “They’ll need our help if we want to keep those species alive.”

Other scientists argue that tinkering with the complexity of habitats is courting disaster — and huge expense.

“Even given our best science, we’re not good at predicting which species will be invasive,” said Jason S. McLachlan, a biologist at the University of Notre Dame who has studied postglacial population spread. “And it’s going to be especially complex as climates change.”

The American beech, for example, was so rare during the ice age that it is rarely found in fossils. “It may have been one of those rare and unusual species we think about saving with approaches like assisted migration,” Dr. McLachlan said. Now, the beech is so abundant in Eastern forests, he said, it is shading out “almost all other species.”

More: http://www.nytimes.com/2009/11/10/science/earth/10plant.html