DURHAM, N.C. – Ocean mammals are at a crossroads, with some species at risk of extinction and others showing signs of recovery, a new study by an international team of researchers shows.

Understanding the threats that continue to pose threats to these majestic creatures and identifying the right conservation measures to reverse their declines is increasingly urgent as human and climate pressures mount.

The study’s authors, who include David Johnston, associate professor of the practice of marine conservation ecology at Duke University’s Nicholas School of the Environment, reviewed the status of the world’s 126 marine mammal species, including whales, dolphins, seals, sea lions, manatees, sea otters, vaquitas and polar bears.

They found that pollution, climate change, and bycatch are among the leading drivers of decline.

“A quarter of these species are now classified as being at risk of extinction on the IUCN Red List, with the near-extinct vaquita and the critically endangered North Atlantic right whale among those in greatest danger,” said Johnston, who also directs the Marine Robotics and Remote Sensing Lab at the Duke University Marine Lab.

On the positive side, conservation efforts have led to the recoveries of other species once also at grave risk, including the northern elephant seal, the humpback whale and the Guadalupe fur seal, he said. It’s incredibly important that these successes are identified and commended.

The new study examines a range of conservation measures, including marine protected areas, bycatch reduction methods and increased community engagement, that could help spur the recovery of even more species, said its lead author, Sarah Nelms of the University of Exeter’s Centre for Ecology and Conservation. It also identifies the species we still just don’t know enough about to know for sure how best to protect them.

She said 21% of marine mammal species are listed as “data deficient” by the IUCN Red List, meaning not enough is known to assess their conservation status. This lack of knowledge makes it challenging to prioritize which of the species are most in need of protection and determine what actions should be taken to save them. These data gaps are greatest for species that inhabit remote places, are often on the move, or are otherwise difficult to spot, track and inspect through traditional field observation methods.

Using technologies such as drones, satellite imaging, electronic tags and molecular analysis can help scientists circumvent these barriers and gather more of the information they need on these elusive species, said Brendan Godley, who leads Exeter’s marine research group.

"Sharing best practices will empower us,” he said, that’s why studies such as the new one, which was published March 25 in the journal Endangered Species Research, are so important.

"Very few marine mammal species have been driven to extinction in modern times, but human activities are putting many of them under increasing pressure,” said Nelms. “We’re at a critical crossroads.”

“Drones and other remote sensing technologies have opened new horizons in our efforts to learn more about these species, the threats they face, and the conservation measures that can help turn the tide before it’s too late,” said Johnston. “This study underscores the need to keep innovating.”

CITATION: “Marine Mammal Conservation: Over the Horizon,” S.E. Nelms, J. Alfaro-Shigueto, J.P.Y. Arnould, I.C. Avila, S. Bengtson Nash, E. Campbell, M.I. Carter, T. Collins, R.J.C. Currey, C. Domit, V. Franco-Trecu, M.M.P.B. Fuentes, E. Gilman, R.G. Harcourt, E.M. Hines, A. Rus Hoelzel, S.K. Hooker, D.W. Johnston, N. Kelkar, J.J. Kiszka, K.L. Laidre, J.C. Mangel, H. Marsh, S.M. Maxwell, A.B. Onoufriou, D.M. Palacios, G.J. Pierce, L.S. Ponnampalam, L.J. Porter, D.J. F. Russell, K.A. Stockin, D. Sutaria, N. Wambiji, C.R. Weir, B. Wilson, B.J. Godley: March 25, 2021, Endangered Species Research. DOI: https://doi.org/10.3354/esr01115