Doha — New estimates have shown that when coastal ecosystems suffer degradation or are converted for aquaculture, upstream dams, dredging or urban development, up to one billion metric tons of carbon is emitted into the atmosphere every year - with over half of that coming from mangrove destruction alone.
Yet as negotiators travel this week to the United Nations climate change summit (COP18) in Doha, Qatar - a country rich in mangroves - it seems that the rapid decline of wetlands has yet to garner the international attention it deserves.
The economic as well as ecological and social costs of coastal wetland conversion will be huge, said Boone Kauffman, an associate with the Center for International Forestry Research (CIFOR) and co-author of Estimating Global "Blue Carbon" Emissions from Conversion and Degradation of Vegetated Coastal Ecosystems.
He put the price tag between US$6 billion and US$42 billion in lost jobs and opportunities.
Greenhouse gas emissions from destruction of marshes, mangroves and seagrasses are so high because these ecosystems sit atop large carbon-rich sediments of previously sequestered "blue carbon". Wetlands are second only to tropical peat swamp forests in the amount of carbon contained per hectare.
"Below-ground carbon stocks in coastal ecosystems are more vulnerable to loss when there is land-cover change compared to the uplands," said Kauffman.
In the last century, 25 percent to 50 percent of the Earth's coastal ecosystems have disappeared due to agricultural and aquaculture expansion, forest overexploitation, industrial use, upstream dams, and other causes, such as the rising and falling sea levels, he said.
"Based on current conversion rates, we could lose 30 percent to 40 percent of tidal marshes and seagrasses within the next century."
Added Daniel Murdiyarso, senior CIFOR scientist: "Considering wetlands contribute up to 19 percent of total emissions from deforestation, their increasing destruction is significant not only for loss of livelihoods, but also for climate change."
Despite a recent request by the United Nations Framework on Climate Change (UNFCCC) to the Intergovernmental Panel on Climate Change (IPCC) to create wetlands guidelines specifically for greenhouse gas emissions inventories to supplement the 2006 guidelines, progress has been slow.
CIFOR has led the way in developing measurement methods and quantifying carbon stocks and values, but Kauffman said given their values and vulnerability greater study is warranted.
"Because coastal wetlands carry important ecosystem services - storm protection, flood attenuation, fisheries production, effects on water quality and strong ecological linkages to coral reefs, for example - they are incredibly important to humanity."
Despite the potential economic costs, little consideration or study have been given to the lost opportunities and values associated with land-cover change, said Kauffman.
"Further, the economic and resource losses to local coastal communities who depend upon mangroves need to be considered - this would include losses of fisheries resources, storm protection, wood and thatch, medicines among others."
The effects of releasing stored blue carbon into the atmosphere would be felt worldwide in the form of droughts, rising sea levels and the frequency of extreme weather events, and it is likely the cost would be most felt in low-income countries.
However, the study notes that the potentially large carbon emissions from degraded vegetated coastal ecosystems may also offer a new carbon mitigation opportunity that could be similar or a part of the reduced emissions from deforestation and degradation (REDD+) program that creates economic incentives to encourage the maintenance of forest carbon storage.
"Climate change mitigation strategies such as REDD+ would have many collateral benefits," Kauffman said, adding that gaining accurate measurements was critical to move this forward.
"We need to conduct more studies to even better quantify the actual emissions from land-cover change and how this differs from region to region and ecosystem to ecosystem."
Mangroves under pressure: Forgotten wetlands in the changing climate, held at Forest Day 6 in Doha, on December 2, will bring together distinguished experts to explore the role that mangroves play in combating climate change, their current status and successful restoration programs. For more information, visit the Forest Day 6 website.