Ocean Life Faces Mass Extinction

Broad Study Says
研究结果显示，海洋生物面临大规模灭绝。

A team of scientists, in a groundbreaking analysis of data from hundreds of sources, has concluded that humans are on the verge of causing unprecedented damage to the oceans and the animals living in them.

“We may be sitting on a precipice of a major
extinction event, ”said Douglas J.McCauley,an ecologist at the University of California, Santa Barbara, and an author of the new research, which was published on Thursday in the journal Science.

But there is still time to avert catastrophe,Dr. McCauley and his colleagues also found.Compared with the continents,the oceans are mostly intact, still wild enough to bounce back to ecological health.

We're lucky in many ways, said Malin L. Pinsky, a marine biologist at Rutgers University and another author of the new report. The impacts are accelerating, but they're not so bad we cant reverse them.

Scientific assessments of the oceans' health are dogged by uncertainty: It's much harder for researchers to judge the well-being of a species, liying underwater, over thousands of miles,
than to track the health of a species on land. And changes that scientists observe in particular
ocean ecosystems may not reflect trends across the planet.

However, there are clear signs already that humans are harming the oceans to a remarkable degree, the scientists found. Some ocean species are certainly overharvested, but even greater damage results from large-scale habitat loss, which is likely to accelerate as technology advances the human footprint, the scientists reported.

Coral reefs, for example, have declined by 40 percent worldwide, partly as a result of climate-change-driven warming.

Some fish are migrating to cooler waters already. Black sea bass, once most common off the coast of Virginia, have moved up to New Jersey. Less fortunate species may not be able to find new ranges. At the same time, carbon emissions are altering the chemistry of seawater, making it more acidic.

Some species have already disappeared. The fossil record indicates that a number of large animal species became extinct as humans arrived on continents and islands. For example, the moa, a giant bird that once lived on New Zealand, was wiped out by arriving Polynesians in the 1300s, probably within a century.

But it was only after 1800, with the Industrial Revolution, that extinctions on land really
accelerated. Humans began to alter the habitat that wildlife depended on, wiping out forests for timber,
plowing under prairie for farmland, and laying down roads and railroads across continues.

Many marine species that have become extinct or are endangered depend on land-seabirds that nest on clifts, for example, or sea turtles that lay eggs on beaches. So human activities on land can also have an impact on marine species.
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