The potential of blue carbon in the Red Sea

Wading knee-deep through dense mangrove foliage in a remote area of Saudi Arabia’s Red Sea is Professor Carlos Duarte, Professor of Marine Science at King Abdullah University of Science and Technology (KAUST) and a father of the Blue Carbon strategy to mitigate climate change through the conservation and restoration of these coastal ecosystems. He delights in the potential to avert a climate crisis that these seemingly ordinary trees have.

"At the beginning of this century, mangrove forests, seagrass meadows and salt marshes were under appreciated components of the marine ecosystem, to the extent that I nicknamed them the ugly ducklings of biological conservation," Professor Duarte says. "Today, blue carbon strategies of mitigating greenhouse gas emissions through the conservation and restoration of these habitats have been adopted by many nations as a key means of meeting their commitments under the Paris Agreement."

Until a decade or so ago, little was known about the immensely important role that mangroves, seagrasses and tidal marshes play in sequestering carbon from the atmosphere and effectively burying, or ‘sinking’, it into the seabed below. Much like their terrestrial plant and tree cousins, mangroves ‘breathe in’ carbon dioxide and ‘breathe out’ oxygen, the reverse of humans and hence one of the cornerstones of the symbiotic relationship we have with nature.

The big difference with mangroves however is that they bury carbon at a rate 30 times higher than that of forests. And that they ‘sink’ this captured carbon, dead wood and leaves by trapping organic carbon in their aerial roots and depositing it into layers of rich marine sediment, where carbon can be stored undisturbed for millennia, as there are no fires underwater. Over time this becomes a dense carbon stock called ‘blue carbon’.

“The term was first coined a decade ago to describe the disproportionately large contribution of coastal vegetated ecosystems to global carbon sequestration,” says a report that Duarte coauthored with a number of UN Agencies, largely building on research he had published. Duarte’s research led to the formulation of the Blue Carbon concept, an achievement for which he was awarded the distinguished BBVA Foundation Frontiers of Knowledge Award in Ecology and Conservation Biology in 2020, among other accolades.

Duarte is fortunate to have the Red Sea as his playground for scientific discovery as the mangroves there have been found to be six times more effective than mangroves in other parts of the world at calcium carbonate dissolution – a process that increases the ocean’s alkalinity and in turn increases its capacity to safely store CO2 from the atmosphere in seawater.

According to KAUST, “carbonate dissolution, combined with carbon burial, gives Red Sea mangroves a huge capacity to be an effective carbon sink - important traits for mitigating climate change”. 

“Pliny the Elder, the Roman historian who lived in AD 23/24 – 79 once asserted that ‘in the Red Sea trees are of a remarkable nature’, as western scientists first discovered mangroves when Roman legions arrived at the Red Sea, and indeed we continue to discover how remarkable they are!” Duarte enthuses.

In addition, a recent KAUST study of Red Sea mangrove forests found that they efficiently capture and store microplastics in their sediments. “Our research brings light to the mystery of missing marine plastic to reveal that mangroves, blue carbon habitats, are hugely efficient at trapping plastics and burying them in their soils where they can no longer harm vulnerable marine life or human consumers,” says Duarte.

With no input from freshwater sources, the Red Sea is also unique in that it is very salty and warm. This has given rise to exceptionally resilient corals, a diverse range of carbon-burying seagrasses and, bucking a global trend of decline, an expanding population of mangroves.

Duarte and his colleagues at King Adbullah University of Science and Technology (KAUST) are putting theory to practice in their partnership with The Red Sea Development Company (TRSDC), where he is a prominent member of its Advisory Board. TRSDC is developing The Red Sea Project, a 50-hotel luxury tourism destination comprising 92 islands, mountains, sand dunes and dormant volcanoes in a relatively sparse and vast area on the west coast of Saudi Arabia. 

Critically, The Red Sea Project has put regeneration at the heart of its development approach, with aims to be powered by 100% renewable energy 24/7 and to actively enhance the environment within two decades.

“The ambition is to create a 30% net conservation impact through the development and to exceed what would be the goals and economical outcomes of this area if it was just declared a national park,” says Duarte. “In the 21st century the mantra to conserve and sustain the little that is left is no longer acceptable. The ambition TRSDC brings to create net positive conservation value has changed my vision of what role the private sector can play in driving towards a healthy ocean.”

Together, TRSDC, KAUST and a number of other academic and scientific institutions involved in the project aim to raise the ambition to a groundbreaking approach for regenerative tourism, one that delivers positive impact and highlights the important global role blue carbon is playing in achieving this goal.