Humans Are Altering the Seas. Here’s What the Future Ocean Might Look Like. (New York Times)
Excerpt from this New York Times story:
But these vast, seemingly timeless seascapes have become some of the world’s most vulnerable marine habitats, according to a new study published on Thursday in the journal Science that adds up and maps the ways human activity is profoundly reshaping oceans and coastlines around the world.
Soon, many of Earth’s marine ecosystems could be fundamentally and forever altered if pressures like climate change, overfishing, ocean acidification and coastal development continue unabated, according to the authors.
It’s “death by a thousand cuts,” said Ben Halpern, a marine biologist and ecologist at the University of California, Santa Barbara, and one of the authors of the new study. “It’s going to be a less rich community of species. And it may not be something we recognize.”
Among the other ecosystems at high risk are sea grass meadows, rocky intertidal zones and mangrove forests. These parts of the ocean, near shore, are the ones people most depend on. They provide natural defenses against storm damage. And the vast majority of commercial and recreational fishing, which together support more than two million jobs in the United States alone, takes place in shallower coastal waters.
The new study tries to measure just how much various human-caused pressures are squeezing, shifting and transforming coastal and marine habitats.
The research began in the early 2000s, when widespread coral bleaching was raising alarm among marine scientists. In response, Dr. Halpern and his colleagues set out to map the parts of the ocean that were healthiest and least affected by humans and, conversely, which parts were the most affected.
The inherent challenge was comparing marine habitats, from coral reefs to the deep ocean floor, and their responses to different human activities and pressures, like fishing and rising temperatures, all on a common scale. They came up with what researchers call an impact score that’s based on a formula incorporating the location of each habitat, the intensities of the various pressures on that habitat, and the vulnerabilities of each habitat to each form of pressure.
Under the world’s current trajectory, the study found, by the middle of the century about 3 percent of the total global ocean is at risk of changing beyond recognition. In the nearshore ocean, which most people are more familiar with, the number rises to more than 12 percent.
That future will look different in different regions. Tropical and polar seas are expected to face more pronounced effects than temperate, mid-latitude ones. Human pressures are expected to increase faster in offshore zones, but coastal waters will continue to experience the most serious effects, the researchers forecast.
There are also countries that are considered more vulnerable because they depend more heavily on resources from the ocean: Togo, Ghana and Sri Lanka top the list in the study.
Across the whole ocean, scientists generally agree that many places will look ecologically poorer, with less biodiversity, Dr. Halpern said. That’s mainly because the number of species that are resilient against climate change and other human pressures is simply far fewer than the number of more vulnerable species.
