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Giving The Ocean A Checkup By Measuring Its Health

The world’s oceans are a vast and complicated–but vital–part of the planet. Scientists are now working on a way to give us a simple indication of how healthy they are. The answer, sadly, may be: not so good.

Giving The Ocean A Checkup By Measuring Its Health
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Later this year, a partnership of international non-profits will release the Ocean Health Index, a metric devised by a consortium of more than 60 international scientists to evaluate what’s going on under the sea–and how humans are affecting it.

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So what’s wrong with the ways that ocean health is assessed these days? “Until now, we really haven’t had a way to measure how the oceans were doing across a portfolio of categories,” says Elizabeth Selig, a marine scientist at Conservation International who contributed to the report. The Index will also use some new measures that show what damage to the ocean does to humanity, as it affects what we eat and how we make a living. “By considering things like food and livelihoods, I think the perspective is changing from one where we’re trying to understand human impacts on the oceans to understand how our actions contribute to our own well-being, as part of a feedback loop.”

The report uses indicators that measure the intensity of the most urgent ocean stressors, including climate change, ocean acidification, overfishing, habitat degradation, invasive species, loss of biodiversity, pollution, and eutrophication (how the ocean responds to artificial chemicals getting pumped into it). In the report, each of the categories will be ranked out of 100 on its present status compared to a reference state, and from -100 to +100 on three factors assessing its probable future state.

The effort is part of a growing movement to quantify ecosystem health in order to help policy-makers set priorities and measure improvements, similar to the way that the Gross Domestic Product squishes together a mass of complex data into a single number for tracking purposes.

Some threats to global oceans have been well-documented already, including the fact that one-third of the world’s corals are at risk of extinction and that 30% of the ocean’s sea grasses have disappeared, a rate that is comparable to terrestrial rainforests.

Selig says that the oceans face threats that are different from environments on land. “One of the things that is a challenge in the oceans is governance–it’s harder to force regulations in ocean environments that lie outside national jurisdiction,” she says. Nations retain sovereignty over marine areas 200 miles off their borders – but outside those places, some countries can band together to create international marine protected areas. Some of Selig’s research published in March showed those special conservation zones provide many direct benefits to fisheries and coral reefs. The downside is that those zones appear to offer limited help to corals in their battle against global warming. “Marine Protected Areas work for local threats like overfishing, but for global threats, we need to look at a suite of tools aimed at reducing activities responsible for climate change,” Selig says.

Unexpected benefits from marine habitats may be less obvious: mangroves and salt marshes provide a physical buffer that prevents erosion and protects from storm surges. Studies document that places with healthy mangroves fared better than those without.

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