Climate change forcing animal and plant migration — and they may need human help

KALAMAZOO, MI — As climate change accelerates, humans are not the only ones forced to adapt. Plants and animals are subject to three choices: stay and evolve, migrate to a new habitat, or face extinction.

On the afternoon of February 14, Dr. David Karowe, a professor in the Department of Biological Sciences at Western Michigan University, gave a talk titled Polar Bears, Maple Trees, and Salamanders: Non-human Migration Due to Climate Change, in which he discussed the influence of climate change on both plant and animal migration. Sponsored by the Kalamazoo Climate Crisis Coalition as a part of their ongoing Fridays for Future series, Karowe addressed the implications of climate change on non-human species. 
 
Dr. David Karowe, a professor in the Department of Biological Sciences at Western Michigan UniversityKarowe noted that “some places that were suitable habitat for a species 50 years ago may not be anymore.”  Scientists are working to understand which species can successfully adapt, and how human intervention can help. 
 
In theory, some species might be able to adapt to changing conditions and not have to migrate; however, for most, this is unlikely “because the pace of climate change is just way too fast for genetic adaptation for most species.” 

Evolution is slow and mutation alone is not fast enough to keep pace with rapid environmental shifts. Additionally, species need to already have the genetic traits that would help them survive under new conditions — but these traits would not have evolved in species that never experienced such extreme temperature changes. 
 
For example, snapping turtles are habitat generalists, meaning that they can survive in numerous environments. They have “a better chance of having some of the genes necessary in at least some of the populations and [they] mature early so generation times [are] short, which means that evolutionary potential is probably greater.” However, Karowe pointed out that research suggests that snapping turtles lack the genetic variation needed to adapt to notable temperature changes. 
 
Many species are already shifting their ranges in response to rising temperatures. The most common pattern sees species move towards higher elevations or latitudes, where habitats are cooler. For example, in Wisconsin, approximately 80% of forest understory plants have moved northward since 1950, “but very few are tracking their climate movement well… so very few are following their climate shifts accurately,” meaning “we've got migrants [that are] sort of confused.” 
 
While some species are moving in the right direction, others are not.  Karowe recalled that approximately 60% of tracked species are moving towards more suitable environments, but about 35% are shifting in ways that do not coincide with warming patterns. While scientists lack comprehensive data on migration trends, especially in marine environments, data has shown that marine species appear to be migrating faster as barriers are fewer in the ocean. 
 
Even species that can move quickly still face significant obstacles. The velocity of climate change — the rate at which conditions shift — is highly variable. Karowe noted that land-based species must migrate at an average rate of 14 km per decade to keep pace with climate change, while aquatic species have to move even faster, at an average of 27 km per decade. Some species have no viable migration options. 

Mountain-dwelling plants and animals have “been described as being on an escalator to extinction,” as they are forced upward until they run out of space. Similarly, river species that migrate upstream may be stranded at the headwaters. 
 
Given the challenges of natural migration, scientists are exploring assisted migration — deliberately moving species to suitable habitats beyond their current range. Karowe used the example of oaks from Tennessee and Pennsylvania. They have successfully been planted in the northern reaches of their respective ranges. However, when moved outside of these existing ranges, they do not do as well. Questions remain about where to relocate species and how to integrate them into existing ecosystems without disrupting present biodiversity. 
 
The future of climate migration is dependent on several factors, including greenhouse gas emissions, habitat availability, and human intervention. Karowe hypothesized that while some commercially valuable species, such as trees used for timber, will likely get more assistance, others — such as subsistence crops grown in the Global South — may not have much support. 
 
Karowe added that ecosystems do not move as cohesive units, making it difficult to preserve integral relationships. Mutualistic fungi, soil composition, and food webs all contribute to a single organism’s survival, making relocation all the more difficult. 
 
Karowe concluded that “very few nonhuman climate migrants are moving fast enough [and] the rate of movement is going to increase [which] leads to the conclusion that to avoid extinction, many species are going to require us to intervene via assisted migration. We are by no means very good at it yet…but I think we're going to have to get in the migration business.”