A group of scientists led by Prof Douglas McCauley from the University of California, Santa Barbara, has found that the same patterns that led to the collapse of wildlife populations on land are now occurring in the oceans.
The marine defaunation experience is much less advanced, even though humans have been harvesting ocean wildlife for thousands of years; the recent industrialization of this harvest, however, initiated an era of intense marine wildlife declines. If left unmanaged, scientists predict that marine habitat alteration, along with climate change, will exacerbate marine defaunation. Image credit: Jenny Huang / CC BY 2.0.
“Wildlife populations in the oceans have been badly damaged by human activity. Nevertheless, marine fauna generally are in better condition than terrestrial fauna. Over the past five centuries, about 500 terrestrial and only 15 marine species have gone extinct as a result of human activity,” Prof McCauley and his co-authors said.
“Marine wildlife populations are as healthy as those on land were hundreds or thousands of years ago,” they said. “However, that may be about to change as the next 100 years promise to present major challenges to marine life.”
The study, published in the journal Science, compares the march of the Industrial Revolution on land to current patterns of human use of the world’s oceans.
During the 1800s vast tracts of farmland and factories beat back forests and sucked up resources that were mined and drilled out of the ground. As a result, many land-based species were driven to extinction.
In the ocean, however, fishing continued to rely on sailing ships clustered in small slivers of near-shore water.
“A lot has changed in the last 200 years. Our tackle box has industrialized,” Prof McCauley said.
Co-author Dr Steve Palumbi of Stanford University added: “there are factory farms in the sea and cattle-ranch-style feed lots for tuna.”
“Shrimp farms are eating up mangroves with an appetite akin to that of terrestrial farming, which consumed native prairies and forest. Stakes for seafloor mining claims are being pursued with gold-rush-like fervor, and 300-ton ocean mining machines and 750-foot fishing boats are now rolling off the assembly line to do this work.”
“Increasing industrial use of the oceans and the globalization of ocean exploitation threaten to damage the health of marine wildlife populations, making the situation in the oceans as grim as that on land.”
Prof McCauley said: “we now fish with helicopters, satellite-guided super trawlers and long lines that can stretch from New York to Philadelphia. All signs indicate that we may be initiating a marine industrial revolution.”
One solution the team highlighted involves setting aside more and larger areas of the ocean that are safe from industrial development and fishing.
“Reserves alone are not enough. We need creative and effective policy to manage damage inflicted upon ocean wildlife in the vast spaces between marine protected areas,” said senior author Prof Robert Warner of the University of California, Santa Barbara.
Among the most serious threats to ocean wildlife is climate change, which according to the scientists is degrading marine wildlife habitats and has a greater impact on these animals than it does on terrestrial fauna.
“Anyone that has ever kept a fish tank knows that if you crank up your aquarium heater and dump acid into the water, your fish are in trouble. This is what climate change is doing now to the oceans,” said co-author Dr Malin Pinsky of Rutgers University.
“Still, the relative health of the oceans presents an opportunity for saving them. Because there have been so many fewer extinctions in the oceans, we still have the raw ingredients needed for recovery,” Prof McCauley said.
“There is hope for marine species that simply does not exist for the hundreds of terrestrial wildlife species that have already crossed the extinction threshold.”
“The ocean’s future is yet to be determined. We can blunder forward and make the same mistakes in the sea that we made on land, or we can collectively chart a different and better future for our oceans,” Prof Warner said.
_____
Douglas J. McCauley et al. 2015. Marine defaunation: Animal loss in the global ocean. Science, vol. 347, no. 6219; doi: 10.1126/science.1255641
