Monitoring walrus from space to understand their plight
1 February 2021
As sea ice retreats dramatically in the Arctic, walrus habitat is changing—and these marine mammals will need our help to secure their future. Understanding how habitat changes are affecting walrus requires broad, detailed, multi-year data about their populations, but currently, we don’t know how many walrus are in the Arctic. Hannah Cubaynes, Rod Downie and Peter Fretwell explain how satellite imagery is making it possible for scientists to monitor walrus over the whole Arctic. In future, citizen science could play a vital role by enabling people to help spot haulouts and count the animals.
It is summer in the Arctic. In the Chukchi Sea off the coast of northwest Alaska, walrus are resting on sea ice over the Hanna Shoal, sliding into the water from time to time in search of clams. As summer ends, the ice will melt and the walrus will swim to Alaska’s shores.
Imagine that you are seeing all this from more than 400 kilometres above the Earth, up in space.
It might seem like it should be impossible. Yet satellites orbiting high in the sky are capturing images at resolutions that allow us to detect individual walrus—and technology may soon enable you to help us spot and count them from the comfort of your home.
Every year as summer sea ice retreats further, walrus gather in larger and larger numbers on beaches and along shorelines, forming what are called haulouts. Understanding what these shifting habitats mean for the animals’ survival is critical—and it requires accurate population counts repeated over a number of years.
Counting walrus offshore when they are resting on ice floes is challenging due to logistics and high variability in temporal and spatial distributions. But if diminished summer sea ice means they are more likely to rest at known locations between summer and early autumn, then counting them at these haulouts becomes more feasible.
Because walrus are distributed across the Arctic, the entire Arctic needs to be surveyed every year to get an accurate count. But it is a vast and remote area—difficult to survey from a boat or plane over a few months. In any case, the noise created by boats and planes tends to disturb walrus and cause panic among haulouts, leading to stampedes. (Field research has also become more challenging for a variety of other reasons during the COVID-19 pandemic.)
Satellite technologies offer the possibility of building a long time-series of population counts without having to visit every haulout. (A time series is a series of data points indexed in time order.) Some satellites capture images with a high level of detail, allowing us to detect individual walrus. Even so, counting them across the whole Arctic is a long process, so crowdsourcing—with tagging studies and aerial surveys to help validate accuracy—is an efficient approach.
The Walrus from Space project, co-led by WWF and the British Antarctic Survey, aims to count walrus across the whole Arctic every year for the next five years. The project will rely on close collaborations with science partners in every coastal Arctic state. Detailed satellite images (at 30 to 50 centimetre resolution) will be obtained from Maxar Technologies, and citizen scientists will eventually be able to help count walrus via a crowdsourcing platform. We will match these counts to sea-ice conditions and other environmental variables to better understand how many walrus are in the Arctic and predict future populations. This, in turn, will inform management decisions. Ultimately, it could help protect these marine mammals as the climate crisis worsens.
The coming year will be a chance to test out all these plans with scientists and some volunteer groups. We hope to launch the citizen science aspect of the project to the general public in 2022.
As the Arctic heats up, will walrus go with the floes? Stay tuned for your chance to help us secure a future for them in the wild.
HANNAH CUBAYNES is a research associate focusing on the study of wildlife using satellite imagery. She is also the technical lead on the Walrus from Space project.
ROD DOWNIE leads the Polar & Climate group at WWF–UK and co-directs the Walrus from Space project.
PETER FRETWELL is a geographic information officer with the British Antarctic Survey. He leads the organization’s Wildlife from Space project.
Chief Advisor, Polar Regions, WWF-UK
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