Planting trees in coastal areas can help stressed coral reefs

6 Oktober 2021

Photo: Pixabay/Kanenori

Planting forests along coastlines in tropical regions could have an unexpected benefit in the sea too: helping save embattled coral reels.

The reason for that is that thicker vegetation in coastal regions could greatly reduce the amount of toxic sediment run-off that reaches coral reefs from land and undermines these reefs’ resilience.

A team of scientists at the University of Queensland has reached this conclusion after studying over 5,500 coastal areas worldwide, of which nearly 85% of coastal areas leach sediment to coral reefs, they have found.

That is troubling because much of the run-off is laced with toxic agrichemicals and land clearing along coastlines increases the amount of pollutive sediments that seep into coastal waters.

In fact, pollution from land in the form of run-offs poses the second most serious threat to the planet’s reefs behind climate change, the scientists say.

“Increased sedimentation can cause aquatic ecosystems to be more sensitive to heat stress, which decreases the resilience of corals to pressures caused by climate change,” says Andrés Suárez-Castro, an expert at the university’s Centre for Biodiversity and Conservation Science.

“If the link between the land and sea is not recognised and managed separately, any future efforts to conserve marine habitats and species are likely to be ineffective,” he explains.

The scientists say that by restoring land in coastal areas and boosting their vegetation, countries and communities can reduce the amount of sediment run-off drastically.

“Reforestation is hugely important as it maintains the stability of soils that are vital in limiting erosion risk: it also helps to trap more sediments and prevent them from reaching aquatic systems,” Suárez-Castro says.

“Building coral resilience through reducing sediment and pollution is also key to improving a coral reef’s potential for recovery. If land management to reduce sediment runoff does not become a global priority, it will become increasingly challenging, if not impossible, to protect marine ecosystems in the face of climate change,” he warns.

If on average 1,000 hectares of forest was restored in each coastal basin, the amount of sediment reaching coral reefs from land could be reduced by 8.5% on average among reefs that spread over an area of 63,000 square kilometres, the experts have discovered.

“Our approach can be adapted with local data to identify optimal actions for preserving ‘win-wins’ for multiple ecosystems spanning the land and sea,” Suárez-Castro says.

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