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- Recently, a study has been published, which has raised scepticism about the efficiency of restoring coastal habitats to offset carbon emissions.
- Restoring Coastal habitats is far from certain and unreliable. and there’s a real risk that the scale at which they can mitigate emissions has been massively oversold.
- It is extremely difficult to work out a reliable figure for carbon accumulation by coastal ecosystems under current conditions.
- There is a very weak basis for calculating the future carbon offsets that restoration projects might provide over the next 50 to 100 years.
Causes of Uncertainty
- Estimates of the rate at which blue carbon habitats remove CO₂ from the atmosphere vary widely.
- Blue Carbon refers to carbon sinks held by coastal, aquatic, and marine vegetation, marine organisms, and sediments.
- Across several hundred scientific studies, there was a 600-fold difference between the highest and lowest estimates for carbon burial in salt marshes, a 76-fold difference for seagrasses and a 19-fold difference for mangroves.
- Burrowing organisms disturb and mix younger and older layers, causing errors in the dating process of fossis fuels by making sediments seem younger, and carbon burial rates greater, than they really are.
- Carbon dating is a radiometric dating method. It uses the naturally occurring radioisotope carbon-14 (14C) to estimate the age of carbon-bearing materials up to about 58,000 to 62,000 years old.
- Much of the carbon buried in coastal sediments comes from elsewhere, such as soil swept from the land and carried by rivers. This is called Imported Carbon.
- In a study on one saltmarsh, the proportion of 50% imported carbon near the sediment surface increased to 80% in deeper layers.
- Since the deeper value represents the habitat’s long-term carbon burial rate, the direct contribution of a restored habitat to removing carbon may be much less important than thought.
- Turning an oil palm plantation back into a mangrove forest or flooding a coastal area to make a saltmarsh should help the land accumulate carbon.
- But that same land could also release more methane(otherwise known as marsh gas) and nitrous oxide – both powerful greenhouse gases – leaving no net climate benefit.
Recommendations
- Blue carbon habitats should still be protected and, where possible, restored, as they have benefits for climate adaptation, coastal protection, food provision and biodiversity conservation.
- Every effort should still be made to halt, and wherever possible reverse, the worldwide loss of coastal vegetation. Blue carbon habitats are, after all, more than carbon sinks – they also protect communities from storms, nurture biodiversity and species targeted for fisheries, and improve water quality.
- The priority must be to double down on emission reductions, only using carbon removal methods to help achieve net zero where their success is certain.
SOURCE: THE HINDU,THE ECONOMIC TIMES,MINT
