Three decades of data on animal migration and movements in the Arctic confirms that they are shifting their behaviours because of climate change.
An international team of environmental engineers and ecologists compiled a database of more than 200 research projects tracking the movements of over 8000 marine and land animals since 1991.
Scientists have been watching individual species for years, they say, but until now there has been no comprehensive source of data over time across different studies, and collected by different researchers in academic, private and government agencies.
The project was led by the University of Ohio, US, and the database – the Arctic Animal Movement Archive (AAMA) – is hosted on Movebank, a research and collaboration platform for animal movement developed by Max Planck Institutes in Germany.
Without it, scientists worldwide would have a hard time quantifying the long-term effects of climate change and other human activity on animals across the Arctic, says Ohio’s Gil Bohrer, a lead author of the team’s paper in the journal Science.
“Ecologists are doing the best they can, but often, movement track data would be lost, researchers retire or move to other positions, the hard drive ends up getting lost, the research notebook is misplaced or thrown away, and then that data is gone,” he says.
The Science paper includes the results from three studies based on the data, showing long-term and large-scale behavioural changes in golden eagles, bears, caribou, moose and wolves that could affect their ability to eat, mate and survive.
One study compared movements of more than 100 golden eagles from 1993 to 2017 and found that immature birds migrating north in the spring arrived in that region earlier after a mild winter, indicating that warmer temperatures may push them to migrate sooner.
Adult golden eagles, which on average start their migration earlier than immature birds, however, did not shift their patterns. That could have consequences for nesting and chick survival, the study’s authors found. In that case, access to comprehensive data gives ecologists better strategies for managing those bird populations.
A second study tracked more than 900 female caribou from 2000 to 2017 and found that more northern herds are giving birth earlier in the spring, while the calving dates of southern populations have not changed.
The calving dates of northern populations are apparently responding to the mean warmer conditions and early spring onset in the Arctic. However, this response of earlier calving dates is risky. The early spring dates are associated with higher weather variation, and events of late deep spring snow are more likely to kill calves born earlier in the season.
The third study analysed bear, caribou, moose and wolf movements throughout the region from 1998 to 2019 and found that they moved at different speeds depending on seasonal temperatures, rain and winter snow.
The ability of many land animals to hunt food is built around their ability to move around large areas of land. The study found that moose and caribou moved more in days with higher temperatures, while their predators, wolf and black bears, tended to move less.
The results suggest, the researchers say, that herbivores will have a harder time finding food and avoiding predators as temperatures continue to rise.
“I would say this is an early example of what we might call global animal movement ecology,” says co-author Elie Gurarie from the University of Maryland, US. “We’re increasing our ability to monitor the pulse of animal populations across the Earth and ask big picture questions about what it means.”