Photo: Tom Kimmerer
In the late summer of 1765, the father and son botanists John and William Bartram paddled upstream on the Altamaha River on the coast of Georgia. The lazy Altamaha meanders over 200 km through the lowlands of Georgia to its mouth in the Atlantic. In 1765, the river was a little-explored treasure for the two botanists in search of new species. Already, though, cotton plantations were encroaching on the Altamaha watershed and destroying some of the natural habitat
The Bartrams found a beautiful little tree unknown to them on October 1, 1765. In 1763, William Bartram returned to the Altamaha and found the tree again. This time, he collected seeds and took them back to the family garden in Philadelphia. There, the tree germinated and soon showed off its gorgeous flowers. William’s cousin Humphrey Marshall named the tree Franklinia alatamaha, after their family friend Benjamin Franklin and the river on which they found the tree.
Remarkably, that was the end of the story of Franklinia in the wild. A few trees were observed by other explorers on the Altamaha, but by 1803, the tree was extinct in the wild. No natural stands or even individual trees have ever been seen on the Altamaha or anywhere else. Like many other botanists, I have paddled the Altamaha convinced that I wold find the tree where others had failed, but it was not to be.
Today, the tree is thriving in Philadelphia and other places, but only because William Bartram collected those seeds and was successful in growing trees from it. Why the tree disappeared from the wild is not known. A disease caught from nearby cotton plantations, changes in the river level, and other explanations have been put forward, but we probably will never know why Franklinia is no longer on the Altamaha.
The Bartram’s accidentally saved a species from extinction. The Bartrams moved a tree from a location where it was doomed to one where it is now thriving, at least in captivity. Today, we call this assisted migration, and it is an important part of plans to prevent trees from becoming extinct as climate to which they are adapted moves out from under them.
Climate change is now upon us, and the great range shuffling of species has begun. Trees, insects, mammals are shifting their ranges in response to the warming climate. This is most evident in high mountain areas, where the uphill movement of species is easily measured. While plants and animals have always migrated in response to changes in climate, the current rate of warming caused by human industrial activity is too rapid for some species to migrate.
This is especially true of trees which are often much slower to migrate than other plants. Trees with large, heavy seeds and fruits that cannot be carried by wind are at a particular disadvantage. For those species, humans may have to play a role to prevent extinction. Assisted migration may be the only way to prevent many important species from becoming extinct.
Foresters have practiced assisted migration for a long time, not to rescue them from climate change but to grow trees for commercial purposes. Today, there are more Monterey pine trees growing in New Zealand plantations than all the Monterey pines within the tree’s original small range in California. Now, however, forestry agencies worldwide are beginning to plan or practice assisted migration to prevent extinction of tree species. For other species like Torreya taxifolia, citizen organizations have taken the lead in ensuring a future for rare and endangered species.
This is the first of a series on assisted migration.