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Saving a Rare Tree Worlds Away

by Rachel Nuwer. The New York Times

A graceful birch native to Japan is one of the rarest trees in the world. Two decades ago, botanists counted just 21 remaining in the wild, all confined to a single stand in the remote, rugged forest of the Chichibu Mountains — likely far too few for the species, Betula chichibuensis, to sustain itself.

Arboretums scrambled to cultivate the tree, with some success. But now the species may have gained a second chance at survival: Botanists in Britain have collected and germinated seeds from these wild birches for the first time in nearly 30 years.

The new seedlings may help restore genetic diversity to the small population of cultivated trees and fuel efforts to reintroduce them in the wild. “Definitely, it’s a great coup for a very rare species,” said Michael Dosmann, a curator at the Arnold Arboretum of Harvard University, who was not involved in the project.

No one knows why B. chichibuensis grew so scarce. Experts now believe that there are more than two dozen in the wild; in recent years, Toshihide Hirao, a forest ecologist at the University of Tokyo Chichibu Forest, has discovered eight other small stands in the mountains. Still, “there is no doubt that this species is very rare and endangered,” he said.

A small stand of Betula chichibuensis trees in the Chichibu Mountains in Japan, the last place where they survive in the wild.

Dr. Hirao and his colleague Satoshi Suzuki led British researchers last year to one of the more accessible patches. The team set out around sunrise on a gloomy October morning, toting plant presses, pruners and GPS units. It was not an easy trek. As they moved deeper into the mountains, the trail became narrow and unruly, often nearly disappearing, said Ben Jones, curator of the University of Oxford Harcourt Arboretum. A drenching rain began to fall as the researchers traipsed over slick limestone outcrops and scrambled over steep hillsides.

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Monday, November 2, 2015