If you're a cetacean, it pays to dive deep.
Large whale species that live in the deeper oceans are recovering, while their dolphin and porpoise cousins along the coasts and in rivers are sliding toward extinction, according to the latest update on the IUCN Red List status update for cetaceans, the order of animals that includes whales, dolphins and porpoises.
Overall, at least 25% of cetaceans remain threatened with extinction, more species were downgraded than have recovered, and scientists said they lack data to assess fully half of the species on Earth. But the report highlights some conservation success stories that are as heartening as they are rare amid reports about the declining health of the world's oceans.
Despite ongoing and controversial hunting (ostensibly for "scientific research") of humpback whales by Japan, the acrobatic and vocal migratory species is no longer considered vulnerable. Southern right whales, too, are no longer at risk of extinction, according to the IUCN, the world's authority on biodiversity and threatened wildlife.
The recovery of these species is due primarily to a hunting ban that most nations of the world observe, according to Randall Reeves, Chair of the Cetacean Specialist Group of the IUCN Species Survival Commission.
Fishing -- often in pursuit of other species -- is the leading cause of death for whales' smaller cousins, like the Irrawaddy dolphin, the finless porpoise and the South American franciscana, all of which are newly listed as being "vulnerable." The vaquita, a Gulf of California porpoise, is likely to go extinct within years, as 15% of its dwindling population is killed in industrial-scale gill nets each year.
Too many of these small coastal cetaceans end up as bycatch in fisheries," Reeves said. "This remains the main threat to them and it is only going to get worse."
The only solution the IUCN identified: Prohibit certain types of fishing for all species in some important marine habitats.
The report also identifies military sonar as a threat. The U.S. Navy has been locked in a protracted legal battle with environmental groups over the use of sonar during military training exercises, because of the purported damage it does to the cetaceans that use sound waves through the water to communicate.
Large parts of the oceans are now filled with human-generated noise, not only from military sonar but also from seismic surveys and shipping. This noise undoubtedly affects many cetaceans, in some cases leading to their death, says Jan Schipper, the mammal assessment director for Conservation International and IUCN. It may not always kill whales and dolphins, but it affects their ability to communicate and it can drive them away, at least temporarily, from their feeding grounds.
Finally, global warming is affecting cetaceans, particularly as warming and acidified waters affect the population and distribution of krill, a major food source for many whales and other marine creatures in the oceanic food Web.
To save whales for future generations, we need to work closely with the fishing industry, the military and offshore enterprises including shippers and oil developers," said Julia Marton-Lefèvre, IUCN director general. "And we need to fight climate change."
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