Monitoring Arctic seals from space
Arctic seals, which depend on sea ice, face an uncertain future. Sea ice in the Arctic is shrinking at a rapid pace and, according to forecasts, could disappear completely as early as the summer of 2035. For harp and hooded seals this would be a disaster. Both use the sea ice to rest, to give birth to their young, and for moulting. To better monitor the two seal species, researchers from the Royal Netherlands Institute for Marine Research NIOZ (Koninklijk Nederlands Instituut voor Onderzoek der Zee) and Wageningen Marine Research have now collected satellite images for the first time as part of a study on the effects of dwindling sea ice on seals in the Arctic, which will be used to count the seals.
Hooded and harp seal pups were and are still massively hunted, almost exclusively for their white fur. In Canada alone, the 2019 permitted quota was 425,000 animals, 5% of which were adults. Because of their remote habitat, their population size can only be estimated, which is subject to large uncertainty factors. Therefore, current assumptions of 650,000 hooded seals and 7.6 million harp seals should be viewed with caution.
The first large-scale census since 2018, conducted this year by a team of Norwegian researchers east of Greenland, where large groups of the two species gather during the mating season, will provide a more accurate view of population numbers. However, because the sea ice is constantly moving due to currents and winds, it is extremely difficult to find the seals. The search therefore required a great deal of effort: from the ship, the researchers searched the sea ice with the help of drones and a helicopter. In addition, reconnaissance flights were launched from Greenland to find the seals.
When scientists discovered larger aggregations of seals, they placed GPS transmitters on the sea ice to track the animals. After most of the major seal haul-outs were found, the seals were photographed from the aircraft. By counting juveniles on these aerial photographs, population size can be estimated.
The Dutch research team, with the help of the Norwegian team’s observations, has now succeeded for the first time in obtaining high-resolution satellite images provided by the space company Maxar Technologies. Objects with a size of 30 centimeters can be detected in the photos, so that the counting of seals is easily possible. With the help of the Norwegian team’s aerial photos, the count from space can be verified.
With the disappearance of sea ice, finding seals is likely to become even more difficult in the future. Satellite imagery thus represents a major convenience in the monitoring of hooded and harp seals, as larger and inaccessible areas can be monitored in addition to the much lower effort required. When counting walruses and whales, other research groups are already successfully using satellite imagery.
The next of the Dutch scientists’ goals is to automate the count using state-of-the-art artificial intelligence techniques, providing a valuable tool for monitoring seal populations and studying the effects of rapidly diminishing sea ice.
Julia Hager, PolarJournal
More about this topic
