Several once endangered species, including the humpback whale, the
northern elephant seal and green sea turtles, have recovered and are
repopulating their former ranges, a study of marine mammals finds. But
returning species create a new challenge: some people interpret the
return of these animals as a hostile invasion. The study presents
strategies for 'lifting baselines' to help manage and celebrate
recovering species.
The research, published in the June edition of Trends in Ecology and Evolution,
suggests that some species, including humpback whales, have reached
population levels that may warrant removal from endangered species
lists.
But returning species, which defy global patterns of biodiversity
loss, create an urgent new challenge for policymakers and communities,
the study suggests. While many people embrace the environmental and
economic benefits of returning species -- many of them large predators
-- others interpret the animals' recovery as a hostile invasion,
encroaching on key fishing and recreation areas, researchers say.
"Most people support the idea of saving endangered species," says
lead author Joe Roman of the University of Vermont's Gund Institute for
Ecological Economics. "But when native species return, it can be a
struggle for communities. After generations away, these forgotten
species can suddenly be seen as newcomers -- or even pests."
The return of North Atlantic gray seals has been blamed in
Massachusetts for declining fishery yields and attracting sharks to Cape
Cod. Some fishermen in Alaska and Washington State blame returning
whales for reducing black cod and salmon stocks. In California, harbor
seal pupping has resulted in temporary closures of public beaches.
"The takeaways here are that conservation clearly can work, which is
important to celebrate given the trend of declining global
biodiversity," says Roman, who is also a professor at UVM's Rubenstein
School of Environment and Natural Resources. "But wildlife managers need
to do a better job of planning for the return of these species to avoid
future conflicts."
Researchers make four recommendations, including: planning ahead for
impacts and adaption with stakeholders; delisting species that no longer
require protection to shift efforts to other species; improving policy
decisions for "nuisance animal" killings by assessing the total costs
and benefits -- economically, environmentally and culturally -- of
returning species; and celebrating conservation successes with the
public.
A recent analysis of 92 marine mammal populations by another team found that 42 per cent were increasing, the researchers add.
BACKGROUND
The study was conducted by four U.S. marine biologists, including
lead author Joe Roman (University of Vermont) and co-authors Meagan
Dunphy-Daly, David Johnston and Andrew Read (Duke University).
For the study, researchers looked at population data for marine
mammals and other protected species. Of the 87 cetacean species (whales,
dolphins and porpoises) examined, 22 are recovering, 15 are endangered,
and 45 cannot be evaluated due to data limitations. Twenty-six species
of pinnipeds (seals, sea lions, and walruses) are secure, and 13 are
endangered.
Great whales represent a major conservation success, researchers say.
Of the 14 species, four have seen dramatically recoveries, three are
stable, and seven cannot be fully analyzed due to data availability. Ten
of 14 populations of humpback whales could be removed from the U.S.
endangered species list this July. This coastal species, popular among
whale watchers, was recently seen off the coast of New York City for the
first time in generations.
Researchers attribute the recovery of these species to global
conservation efforts, especially national and international wildlife
protection acts, such as the Convention on Trade in Endangered Species
and the U.S. Endangered Species Act, which have reduced commercial
hunting, protect habitats, control invasive species, and guide
reintroduction efforts.
SOME SUCCESS STORIES
The report highlights success stories involving marine species, plus
several notable recoveries of land mammals and birds. Examples include:
North Pacific Humpback Whale: After being reduced by commercial
exploitation to fewer than 1,500 individuals in the 1970s, these whales
have increased by about 6 percent per year and now number 21,000 whales.
This increase is roughly 14 fold in less than 50 years.
Australian Humpback Whale: By the 1960s Australia's two populations
of humpback whales dropped to fewer than 800 individuals. They have
increased at or above 10 percent annually since the cessation of
commercial whaling, and their population is now estimated at more than
40,000.
Northern Elephant Seal: Reduced to as few as 20 individuals through
overexploitation in the late nineteenth century, these seals are now
approaching their carrying capacity of more than 200,000 seals in the
North Pacific.
Sea Otter: After more than 100 years of commercial exploitation, the
North Pacific sea otter was reduced to about 1,000 individuals in 13
groups during the nineteenth century. After protections from hunting and
reintroduction efforts from Alaska to Oregon, their population is now
more than 107,000.
The American alligator, bald eagle, brown pelican, gray whale, and
more than 20 other species have recovered and been removed from the U.S.
list of Endangered and Threatened Wildlife. These examples show that
conservation efforts can lead to recovery of species and ecosystems,
researchers say.
LIFTING BASELINES
Fisheries scientists used the term "shifting baselines" to mark
generational declines in species and stocks. The study authors say the
conservation successes outlined above are important examples of "lifting
baselines."
While these findings highlight several important conservation
successes, the researchers note that more species are declining
worldwide than growing. Large predatory fish have declined by two-thirds
in the past century, and at least three species of marine mammals have
gone extinct since the 1950s
This story is taken from Science Daily
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