First research to estimate ‘blue carbon’ storage in South Africa is helpful for local weather technique

Marine ecosystems have a useful position to play in mitigating the consequences of local weather change. That’s as a result of such ecosystems – and, significantly, vegetated tidal ecosystems like mangroves and salt marshes – seize and retailer a significant amount of atmospheric carbon dioxide (CO₂). CO₂ has accrued in Earth’s environment at unprecedented ranges since the industrial revolution. Scientific proof exhibits that is the primary driver of climate change.

“Blue carbon”, the time period used to explain CO₂ absorbed by marine ecosystems, was an important topic of discussion ultimately yr’s COP27 talks in Egypt.

Extra international locations are bringing blue carbon into their local weather change plans and insurance policies. Indonesia, for instance, has made climate adaptation and mitigation efforts that focus on blue carbon a key part for attaining its Nationally Determined Contributions goal by 2030.

However, partly due to gaps in scientific data, international locations might not understand how a lot potential blue carbon they’ve or the place it’s positioned. There are additionally ecological, social and financial features to think about. These differ from place to put, so (though guidelines exist and international locations can be taught from one another) a “one dimension matches all” method isn’t helpful.

South Africa is globally recognised for its marine heritage. Its marine ecosystems are usually not solely lovely and various: in addition they convey financial and social advantages via job creation and contributing to meals safety. This makes it an crucial to implement focused local weather change insurance policies for marine and coastal ecosystems – and to centre blue carbon in these plans.

Our recent study was the primary nationwide blue carbon sink evaluation for South Africa. It provides a complete estimate of blue carbon storage throughout the nation. That’s an essential factor in supporting the event of evidence-based blue carbon methods.

Whereas nationwide blue carbon shares are naturally restricted by the distribution of mangroves, salt marshes and seagrasses; South Africa does have present insurance policies that can be utilized to guard and restore these ecosystems.

Making a database

Mangroves, salt marshes and seagrasses are the definitive blue carbon ecosystems. Not like forests, or different terrestrial ecosystems, greater than 90% of the carbon is locked into the soil fairly than within the crops themselves. The soils of blue carbon ecosystems are waterlogged with salty seawater. This prevents the saved natural carbon from being transformed again to CO₂ via remineralisation. If left undisturbed and topic to sure situations, these carbon shares can construct up over centuries.

In whole, we discovered that blue carbon ecosystems in South Africa cowl a comparatively small space of round 18,500 hectares. That represents solely 0.015% of the whole land space. It’s because mangroves, salt marshes and seagrasses can solely happen in estuaries with sure environmental situations, making their distribution quite limited.

Learn extra: Mangrove forests won’t be able to spread further in South Africa, so protecting them is crucial

Subsequent, we wanted to calculate how a lot CO₂ these blue carbon ecosystems maintain. To take action, we collated the details about the place mangroves, salt marshes and seagrasses happen with the obtainable information from research which have measured carbon shares.

Utilizing guidelines developed by the UN’s Intergovernmental Panel on Local weather Change, we additionally estimated CO₂ emissions from blue carbon ecosystems for the interval from 1930 to 2020. These emissions are linked to sure human actions. For instance, if a salt marsh is totally eliminated and changed with arduous infrastructure, it’s assumed that each one the carbon it saved has been misplaced and transformed again into CO₂.

Nevertheless, if a few of the pure space stays, then solely a portion of the carbon inventory has been misplaced, significantly if the soil continues to be intact, as that is the place many of the carbon is saved.

We estimated that whole ecosystem carbon shares per unit space (in megagrams of carbon per hectare) vary from 253-534 Mg C ha⁻¹ for mangroves to 100-199 Mg C ha⁻¹ for salt marshes and 45-144 Mg C ha⁻¹ for seagrasses. That is greater than the highest three vegetated pure terrestrial ecosystems in South Africa: indigenous forest, grasslands and thicket.

We additionally discovered that 26%, or about 6,500 hectares, of the historic extent of blue carbon ecosystems has been misplaced via human actions. This has led to historic emissions on common of 30,266 tonnes of CO₂ per yr. For comparability, the CO₂ emissions per passenger on a flight from Johannesburg to Durban is estimated at 0.0736 tonnes of CO₂ per yr: one individual would wish to make the journey about 400,000 occasions in a yr to equal the emissions misplaced from blue carbon ecosystems.

Among the degraded blue carbon ecosystems may very well be restored. Performed efficiently, this might enhance the whole annual carbon sequestration of blue carbon ecosystems by 18%.

Blue carbon future

Our findings provide essential details about South Africa’s blue carbon ecosystems. Defending and managing these ecosystems, we argue, must be built-in into coastal administration practices, biodiversity conservation, nationwide and provincial local weather adaptation methods, and blue economic system planning.

This received’t require new legal guidelines. South Africa has a variety of present insurance policies and measures that can be utilized to achieve these objectives. However it’s going to require a concerted effort throughout all spheres of presidency (native, provincial, and nationwide) to prioritise and mainstream blue carbon ecosystem safety and sustainable use.

Our research recognized principal local weather change mitigation alternatives with co – advantages for adaptation and biodiversity conservation. These embody conservation and rehabilitation actions that can be utilized underneath article 6 of the Paris Agreement underneath marked based mostly approaches to service Agriculture, Forestry and Different Land Use sectoral targets of the local weather change mitigation system for South Africa.