About 71% of our planet’s surface is water-covered with the oceans alone holding 96.5% of all the water on Earth. And it also happens to be the largest carbon sink that absorbs most of the carbon released into the atmosphere. And the carbon captured by the oceans and the rich coastal ecosystem has a name to it; blue carbon.
In the past century, man has taken over as the largest source of CO2 released into the atmosphere. The burning of fossils and biofuels releases a huge amount of carbon into the atmosphere and this has upset the balance. Rising CO2 levels caused by uncontrolled use of fossil fuels, indiscriminate deforestation, and over-reliance on meat as a source of food have led to a rise in global temperatures and brought about major climate changes.
The Blue Carbon Sinks Sequester More Carbon Than The Land-Based Ones
The oceans and the coastal ecosystem are natural sinks for these greenhouse gases through the sequestration of this carbon. The mangroves, salt marshes, seagrass growing along the coastal lines around the world serve to capture and hold carbon. And though these coastal regions are less than the forests of the world, take in carbon at a much faster rate. And they can continue doing so for millions of years.
The carbon sucked in by these oceanic ecosystems is stored underground, and they are there for thousands of years. Over 75% of the nations on earth have their own blue carbon biome. And recognizing the importance of marine vegetation for its ability to take in blue carbon, efforts are on to protect such vital wetlands to offset the ravages of climate change.
How Can Blue Carbon Be Stored?
Algae and marine plants extract CO2 through the process of photosynthesis and this process continues all through their growth progression. And with their death, the organic matter settles to the floor of the ocean and the carbon becomes embedded in the soil under the ocean. It remains there, undisturbed for ages unless disturbed by man.
Two-thirds of the carbon present on the planet is present in the oceans, and they take in a quarter of the CO2 emitted, a lot by human activity through the burning of fossil fuels and the destruction of forests for agriculture. And it is the direct human impact that has upset the atmospheric balance.
Coastal ecosystems are a mere 2% of the entire coastal area. But they contribute around 50% of the carbon that is trapped in ocean deposits. And more carbon is stored per acre than in the forests on land; around 3 to 5 times faster, which is equal to a billion barrels of fossil fuel in a year.
The Significance Of Blue Carbon
The land forests are being depleted at an alarming rate, as agriculture, logging, human habitation, and industrialization is taking their toll. The US has lost over 50% of its wetlands to ‘development’ at the rate of more than 60 acres every hour. And the rate of depletion has been going up. The loss of wetlands along the coastline from 2004 to 2009 has been at the rate of 80,000 acres every year in the US alone.
And the loss of every acre makes it more difficult for humans to tackle the rising temperatures. The loss of every wetland means that lesser carbon gets sequestered. And the destroyed wetlands also release the carbon trapped inside for centuries into the atmosphere.
For instance, when mangroves are cut down, they contribute 10% of the total emissions that are linked to deforestation. the mangroves are going down at the rate of 2% each year. Destruction of the peatlands causes the vegetation to decompose fast and release tons of greenhouse gases. So the destruction of areas that produce blue carbon hit us even harder.
The destruction of the coastal ecosystem releases around 1.02B tons of CO2 into the atmosphere each year. That is about the annual emissions by Japan. It emphasizes the importance of the coastal ecosystems and the blue carbon that they sequester. Even though covering a much lesser area, the coastal ecosystem can bring in greater benefit than the forests in sequestering carbon. Jest cutting down the loss of coastal wetlands by 50% could bring down emission levels equal to that discharged by Spain every year.
Besides storing up on the blue carbon, the coastal ecosystems protect the livelihood of millions by ensuring clean water that helps in fishing and tourism. For instance, the peatlands of Alaska trap blue carbon and also yield food for the dwindling salmon stock.
The Sundarban mangroves are one of the most diverse ecosystems on earth and home to the Royal Bengal tigers. Birds flying along the Pacific and Atlantic flyways get temporary shelter in the wetlands along the route. They are also home to the Louisiana black bear and the Florida panther. The wetlands also protect against erosion, flooding, and rising sea levels. Coasts protected by mangrove forests escaped the brunt of the 2004 tsunami.
But the primary importance of the wetlands remains in their ability to trap and retain blue carbon. Bringing down the release of greenhouse gas reduces the threat to the climate. Removing atmospheric carbon would remain a challenge even if emission levels miraculously went down to zero, and that is not going to happen soon.
Carbon sequestration has been invariably linked so far to reforestation, the preservation of the existing forests, and other solutions that concentrated on the land area. But the importance of blue carbon was felt from the last decade of the previous century as it became the center of study and protection efforts.
Protecting the coastal ecosystem that helps in producing blue carbon remains more cost-effective and also effective than a land-based solution for sequestering carbon. Experts peg the cost of abating carbon dioxide from the mangrove forest to be below $10 a ton.
Simple and cost-effective measures such as preventing nitrogen runoff into wetlands, primarily caused by agriculture, and restoring tidal flow could provide immediate and nonstop climate benefits, as against the unrelenting effort and time expended on land-based restoration efforts.
While tidal flow reduces methane and carbon dioxide from escaping from the wetlands, controlling nitrogen runoffs significantly diminishes the discharge of nitrous oxide also a greenhouse gas), and carbon dioxide into the atmosphere.