As climate change accelerates, an increasing number of plants and animals will be thrown against the ropes. Models indicate up to 30 percent of species are at high risk of extinction due to climate change by 2100. Environmental shifts, scientists say, will happen too fast for many species to migrate to areas with more comfortable conditions. To make matters worse, human infrastructure in the form of highways, farms, and cities now block many natural migration corridors.
To prevent extinctions, some scientists have proposed moving species to new habitats they won’t be able to reach on their own. Also known as assisted migration, assisted colonization, and managed relocation, the idea of giving plants an animals a ride to new ranges for conservation purposes has begun to gain traction. For example, in 2013, the International Union for the Conservation of Nature released “Guidelines for reintroductions and other conservation translocations.”
Among the first to test whether scientists could successfully predict suitable new sites for species affected by climate change was University of Durham biologist Steven Willis. Willis examined the current environmental requirements of two butterfly species, the marbled white and small skipper. In 2000, he then introduced them into areas identified by his model that were 65 and 35 km north, respectively, of their current ranges. Surveys conducted eight years later indicated the populations were still thriving.
In what might be considered a more ad hoc effort, citizens have taken matters into their own hands. Natural populations of Torreya taxifolia, a conifer native to Florida, have nearly stopped reproducing due to a fungal pathogen. Concerned that global warming is exacerbating the tree’s demise, volunteers are now planting fungus-free saplings in forests from North Carolina to New York.
Not everyone, however, is on board with this degree of tinkering. Examples of intentional translocations gone awry abound—think of the cane toad in Australia, feral pigs in California, and kudzu in the American South, to name a few. These catastrophes happened because we can’t predict with confidence which species will play well with residents, and which will morph into invasive species.
Those who frown on actively moving organisms, however, can be more comfortable with shoring up the climate resilience of species in other ways. For example, in the Sierra Nevada, scientists sought to identify which of 17,000 high elevation meadows had experienced the least temperature changes over the past century, as these sites could function as climate refuges for native species. They also analyzed genetic connections between each meadow’s resident Belding’s ground squirrels. Sites with the most squirrel family lineages, they reasoned, are the most connected and reachable by animals looking to relocate, and are worthy of conservation prioritization.
Climate resilience is now shaping plants selected in both wetland restoration and art projects. To select species for restoration sites around the Bay Area, Point Blue’s Students and Teachers Restoring A Watershed (STRAW) project uses a matrix that considers conditions species can withstand (such as drought and fire) and characteristics such as when they provide food to wildlife. This approach has produced a more diverse palette of plants that can tolerate a broader range of environmental conditions while supplying herbivores throughout the year.
And at Sagehen Creek Field Station near Truckee, environmental artists Heley Mayer Harrison and Newton Harrison have embarked on a 50-year project to plant native species at higher elevations than they are typically found in to help them become resilient to warming and the effects of altitude.
As the idea of assisted migration has taken hold, even governments have been getting into the act. Since 2009, the forestry ministry of British Columbia has been planting many thousands of seedlings from more than a dozen timber species outside their natural climate ranges in plots from the Yukon to southern Oregon. The idea is to see which will survive under what conditions. In the meantime, the BC government has also been authorizing timber companies to replant tree species up to 1,600 feet higher than their current native range.
Such experiments will take decades to produce results, but with climate change advancing each year, there’s no time like the present to get started. KMW