Like all living things, trees have a comfort zone where they grow best and thrive-an evolutionarily determined combination of sunlight, soil nutrients, water and temperature that supports the structure, bark, and leaves of diverse species. But what happens when a tree no longer gets the moisture and nutrients it needs to put down roots and send up shoots in a hotter, drier world? While the mighty oak in your front yard can’t just up sticks and trot down the block to the yard with the fancy sprinkler system, trees do have the ability to migrate in response to environmental change, about ten miles per decade, through various modes of seed dispersal. In the United States, trees move in two directions, gravitating toward cooler temperatures in the North or increased rainfall in the West. However, when the rate of change in temperature or precipitation exceeds a species ability to adapt or migrate, climate-induced dieback can occur, negatively impacting the resilience and sustainability of forest ecosystems.
In anticipation of increased global warming, researchers at the Schoodic Institute at Maine’s Acadia National Park are conducting experiments in assisted tree migration—planting and monitoring non-native, heat and drought-resistant seedlings to determine which species will adapt best to projected climatic changes in Acadia in the coming decades. Deciding which trees to relocate and which to leave behind is a tricky business. Altering one component of a natural system can result in cascading changes that may impact the survival of interdependent, co-evolved plants, and wildlife. What future forests will look like, who decides and whether or not trees should be assisted to migrate is a matter of ongoing controversy and debate. Time will tell if those tree species that just can’t get there from here will be able to survive in a warming world with a little travel assistance from their friends in forest ecology. You can learn more about the science of trees on the move from our planting partners at American Forests here.