Life is a juggling act for animals in the Arctic. Seasonal signs, such as warmer spring temperatures or colder fall temperatures, tell animals when to migrate, when to mate, and when to find food and where to find it. This natural schedule is practiced by predators and prey, birds and mammals alike, and a change of only a few days or weeks could have unknown effects on these animals and ecosystems.
According to a new study recently published in Science and sponsored in part by NASA’s Arctic-Boreal Vulnerability Experiment, these changes in the seasonal schedule are already starting, while shifts vary between species and populations (ABoVE).
The researchers analyzed data from the Arctic Animal Movement Archive (AAMA), a compilation of data from more than 200 research studies that from 1991 to the present monitored almost a hundred species, in combination with NASA temperature, precipitation, snowfall and topographic data.
They noticed that patterns of animal movement in the Arctic are changing in various ways that could threaten entire ecosystems.
Gil Bohrer, a professor and environmental engineer at Ohio State University in Columbus, says, “The Arctic is showing more and more extreme signs of climate change,” Sea ice is diminishing, rainfall and snowfall are changing, and in some areas the Arctic tundra is turning green and in others brown. Bohrer said, “Arctic animals respond to these changes, they respond quickly, and that response is not equal,”
Three examples were the subject of the team: a long-term study of eagle migrations, a major study of caribou populations and a multi-species study based on many species of predators and prey.
In the eagle study, researchers analyzed when, based on National Oceanic and Atmospheric Administration (NOAA) data collected from 1991 to 2019, eagles left their winter roosts to migrate north for the summer. On average, migration started about half a day earlier each year – a transition that added up to a 25-year shift of almost two weeks. “Basically, climate change is driving them to move north earlier,” Bohrer said.
The transition was more pronounced in adult eagles than in fledglings, indicating that fledglings might be missing the mating season or that before their food sources, adult eagles enter their summer roosts.
Researchers do not know, however, whether these changes favor various species, ecosystems or individuals or damage them.
For instance, in the caribou analysis, some populations of caribou were seen to adapt to changes in their climate.
Bohrer says we’re likely to see certain animals, people and communities benefiting from climate change and others being affected by it. “But the fact that we’re seeing changes shows that something big is going on,” explains Bohrer.
Typically, in the fall, caribou marry, become pregnant in the winter, and raise their young when food is available in the spring; this schedule is closely associated with environmental trends.
The team studied five caribou populations and found that populations living in the northern Arctic had offspring earlier to match changes in their ecosystem, indicating that these populations are responding to climate change – where things are changing faster due to climate change. By comparison, at the normal time, southern caribou populations, undergoing less rapid environmental change, had their offspring.
The timing of offspring was also affected by the elevation of the home range of the population.
The elevation details came from ArcticDEM, a public-private collaboration funded in part by NASA to construct digital elevation models.
Finally, the researchers used data from multiple studies in the AAMA database to establish how higher temperatures and increased precipitation impact distinct predator and prey species-black bears, grizzly bears, caribou, moose, and wolves.
NASA Daily Surface Weather and Climatological Summaries, or Daymet, provided data for temperature and precipitation in the form of rain and snow.
Species movement trends varied widely: some species move more when summer temperatures are higher, while others move less, during winters with higher snowfall, moose and wolves move less, and increased summer rainfall did not appear to alter movement patterns for any species.
Overall, however, the predator species tended to shift differently.