Scientists Use Assisted Migration to Rescue Tress From Inhospitable Climate Conditions

Scientists are trying to use assisted migration on trees to rescue them from inhospitable climate conditions and hope that this helps them survive climate change.

Over 2,000 seedlings of longleaf pine have been planted by Maryland's Nature Conservancy Plum Creek preserve (TNC) since 2013. Even if scientists think these pine trees should not be planted outside their natural geographical range, which includes Plum Creek, an experiment on these young trees is currently being conducted that aims to see if the intervention can help them migrate northward as their standard range becomes slowly altered by climate change.

Left to their own devices, trees can migrate to favorable habitats conditions via seed dispersal. This is a process where seeds get dispersed by wind or the droppings of birds to newer locations. They can take root if the water, temperature, weather, and other environmental conditions allow them to.

Compared to the approaching climate change, however, this is a prolonged process, too slow for many tree species to survive extinction from fast-warming temperatures.

This spurred scientists to try assisted migration by planting seedlings in locations outside the species' natural range to try to rescue them from harsh conditions caused by climate change.

Some scientists are not convinced, saying assisted migration is expensive, risky, and it is "playing God." TNC's restoration ecologist Deborah Landau, however, thinks longleaf pine are not capable of migrating quickly enough from the fast rate in which climate change is progressing.

Longleaf pine trees once covered 90 million acres in the southeastern US, but now it is only occurring in 3% of its traditional range. Landau says it was practically within the Chesapeake Bay 400 years ago. But due to human incursion, longleaf pine forests have been decimated by fire suppression and logging, fragmenting their growth.

When species do migrate northward, they do not experience smooth colonization of their landscape because of roads, houses, and other human development, according to Landau. But even if their migratory path is unobstructed, the changes brought about by shifting climate conditions are too quick for them to adapt adequately.

Such urgent need fuels the urge to conduct assisted migration not only at the Plum Creek Preserve but also in six other sites under the project Adaptive Silviculture for Climate Change (ASCC).

It aims to assist land managers in how to facilitate and help forests adapt to the changing climate, such as the project's introduction of white spruce and red oak in the Chippewa National Forest in Minnesota.

ASCC researcher Jim Guldin says such trials are supported by sound science but also points out that this is experimental work. Being experimental is what makes scientists concerned about its risks. Two of these are ecologists David Simberloff and Anthony Ricciardi, who contended that such a strategy would likely produce many unpredictable and unintended consequences, as well as to interrupt established food webs and ecosystems profoundly in the areas where foreign trees will be planted. They call assisted in ecological migration gambling.

Guldin says that the introductions are conducted in small steps. In contrast, Landau says longleaf pine requires specific management such as regular burning of surrounding areas to enrich the soil, kill insects that are harmful to them, and eliminate competition from other vegetation.

Management also will not be cheap, and it will be labor-intensive. Guldin agrees that for now, limited applications are feasible.