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Researchers on a boat off the southern coast of Australia recently began throwing some 50,000 bags of sand into the ocean. Their goal is to restore about two dozen acres of seagrass on the ocean floor that will suck carbon out of the atmosphere.

The move is part of an intensified push in some countries to slow warming temperatures on the planet by not only preserving or restoring trees—which also absorb carbon—but also by mending habitats along the world’s coastlines.

These so-called “blue carbon" areas, which aside from meadows of underwater seagrass also include mangroves and tidal marshes, often store more carbon per acre than forests and hold it for a long time, scientists say. From Australia to Colombia to the U.S., these coastal zones are becoming a priority for conservation and restoration as researchers and policy makers start to appreciate their potential to take carbon out of the atmosphere.

Carbon released into the atmosphere from man-made sources such as fossil-fuel-burning power plants and cars is contributing to a warming climate, many scientists say, which is why researchers are seeking ways to capture and store it.

“We looked at our coastal ecosystems and we realized there is actually quite a large potential there," said Neil McFarlane, an official overseeing climate-change strategy for South Australia, one of the country’s six states. “Blue carbon is a whole area that we believe hasn’t been explored nearly hard enough."

Like forests on land, such coastal habitats store carbon in the plants themselves. But areas such as the seagrass field that Australian researchers are aiming to regrow store even more carbon in the soil below. That is because the ground in coastlands that contain seagrass, mangroves and marshes is routinely covered with water and sediment, lowering oxygen levels. This slows decomposition, which normally releases carbon back into the atmosphere.

There are blue-carbon ecosystems around the world, but Australia is a hot spot for them—it has as much as 32% of the world’s seagrass, mangroves and tidal marshes, according to one study. That has prompted the Australian government and local researchers to take a leading role in investigating the ability of coastal ecosystems to store carbon, scientists say.

There is growing interest in revitalizing these areas because it is a natural solution that can slow climate change. New technology, such as machines that take carbon out of the air, is expensive on a large scale.

“We’ve got more attention being drawn to nature-based solutions to climate change," said Peter Macreadie, a marine-science professor and head of the Blue Carbon Lab at Deakin University in Australia. “We’re going to rely on nature to regain control of the planet’s thermostat."

In the U.S., scientists have already restored a different type of seagrass on the east coast of Virginia near the Chesapeake Bay, and some members of Congress, including Sens. Lisa Murkowski (R., Alaska) and Sheldon Whitehouse (D., R.I.), have pushed to investigate further blue-carbon opportunities. In Pakistan, local authorities and private investors are seeking to replant more than 800 square miles of mangroves.

In Colombia, a project to protect mangroves and marshes was approved by Verra, a U.S.-based nonprofit that oversees a carbon-credit program, as its first blue-carbon conservation project. That means the project can issue Verra-certified carbon credits, which represent carbon that has been reduced or removed from the atmosphere. Companies can finance a project to earn carbon credits or buy the credits as a way to offset their own emissions.

In Australia, the researchers tossing the sand-filled bags into the ocean are betting that seagrass seedlings from one local species will float by and attach to the sacks, which are made of burlap, using a special hook at the base of the plant. Other restoration efforts in the country include one from the environmental group Nature Conservancy to restore mangroves and salt marshes in some 500 acres along the South Australian coast.

Australia’s government recently said that it would invest more than $20 million in blue-carbon projects, part of a roughly $75 million initiative aimed at protecting the ocean, though center-right Prime Minister Scott Morrison has been criticized by environmental groups for not moving fast enough to reduce emissions. Australian regulators are also working with scientists to develop their own carbon credit specifically for blue-carbon initiatives.

Storing carbon in coastal areas alone isn’t expected to fully mitigate climate change. Blue-carbon ecosystems are much smaller in extent than land-based forests, so preserving and restoring coastal habitats would make up only a small amount of the carbon reduction needed to meet climate targets. In addition, rejuvenating some coastal areas, such as using divers to replant seagrass, can also be more difficult and costly than planting trees on land.

Still, failing to protect existing seagrass, mangroves and tidal marshes could allow climate change to accelerate, scientists say. If these areas are destroyed, stored carbon gets released back into the atmosphere.

One study, using satellite imagery, found that 2% of the world’s mangroves, or 1,300 square miles, disappeared from 2000 to 2016. In Australia, another study estimated that more than 600 square miles of seagrass had been lost since the 1950s from indirect causes such as heat and light stress.

In 2011, a marine heat wave damaged 36% of the seagrass meadows in Western Australia’s Shark Bay—which has the largest carbon stocks of any seagrass ecosystem world-wide, according to one study. A few years later, mangroves along a 600-mile stretch of coastline in northern Australia died, an event scientists attributed to factors including drought and high temperatures.

“A lot of people don’t really know what seagrass is or what it does," said Jason Tanner, the government scientist overseeing South Australia’s seagrass restoration, adding that it has other benefits like protecting against coastal erosion and providing a habitat for marine life. “I think it is slowly percolating into people’s awareness."

This story has been published from a wire agency feed without modifications to the text.

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