Regional variation in green-up timing along a caribou migratory corridor: Spatial associations with snowmelt and temperature

How do drivers of plant phenology vary across space? We looked at patterns in green-up timing in the Kangerlussuaq-Sisimiut region of West Greenland to learn more about caribou, climate change, and plant phenology.

Between the Davis Strait and the Inland Ice Sheet, the climate regime shifts from a maritime climate to a continental one. On the coast, lots of snow and “mild” temperatures; inland, snow is less persistent, and winters are extremely cold while summers are extremely hot (compared to the coast). Caribou migrate each spring from the coast inland, where they give birth during their summer calving season. This migration runs counter to the direction of the spring “green wave”: Spring plant growth is earliest near the ice sheet, and begins later near the coast.

We found that while snowmelt timing was a better predictor of green-up timing on the coast, spring temperature was a better predictor closer to the Ice Sheet. This is perhaps not too surprising given what I mentioned about the climate regimes above, but our results indicate that if climate change doesn’t uniformly affect temperature and precipitation, the typical spring green-up pattern in the region could be disrupted. Depending on what cues caribou use to time their migration, regional change could throw a wrench in their movement strategy.

Caribou in this population tend to arrive at the calving grounds alongside the emergence of several key forage species, and the timing of plant growth affects caribou reproductive success. Surprises leading up to and during the calving season may spell trouble for these animals. These caribou have a fairly short migration. In other populations and species, migrants move 1000km+ annually. Whether it’s a “short” route like West Greenland, or a long-distance migration (e.g. Arctic Terns), animals integrate the conditions they face en route to their destination.

Understanding the dynamic responses of landscape phenology to environmental conditions will be important for forecasting effects of climate change on migratory animals. There is a lot more to be done in this realm, but this work is a decent starting point for getting at the sum of the region’s spring.