West Indian coral reefs under threat

Climate change is threatening the biodiversity and future of nearly half of the coral reefs and fishing protected areas of the Western Indian Ocean, a new study co-authored by Australian scientists has revealed.

About 50 per cent of the coral reefs and dozens of the coastal and marine ecosystems marked as Marine Protected Areas (MPAs) off the east coast of Africa are at serious risk of being compromised.

Only seven per cent of the coral reefs are in climate refugia - that is, they remain relatively resistant to contemporary climate change - and less than a quarter of those are protected, the joint study by scientists at Macquarie University and the University of New Caledonia say.

"Unless climate-smart adaptive management approaches are adopted, taking into account climate refugia, future biodiversity hotspots, and exposure to climate change, the biodiversity outcomes of MPAs will be seriously compromised, along with their capacity to support the needs of human communities," the study published in the journal One Earth says.

"This is particularly true in low- to middle-income countries where communities are highly dependent on natural resources for their livelihood."

While the MPAs are static, the ocean is not. Understanding how to adapt to these changes and the impact they have on ecosystem functioning and socioeconomic wellbeing is vital for biodiversity conservation, the report said.

"MPAs are among the most effective management responses to human environmental impacts. However, their capacity to sustain biodiversity and associated ecosystem services under climate change is uncertain," it said.

"Here, we show that climate change could render the current MPAs network in 12 nations in the Western Indian Ocean ineffective in supporting conservation and socioeconomic outcomes."

Only four per cent of reefs and six per cent of MPAs were located within areas less likely to experience climate shifts, while biodiversity hotspots for coral and reef fish appeared to be over-represented in the most at-risk areas, the study found.

Scientists counted hundreds of fish and corals species in reefs and MPAs across the Western Indian Ocean as part of the study.

The current spatial arrangement of the MPA network may not conserve the most diverse and functional reefs in the future, and as the ocean changes, there will be a "species reshuffle".

As such, the static MPAs might not do their job of promoting biodiversity persistence and resilience to climate change, they said.

But changes could and should be made, they added.

"A portfolio of less biodiverse yet strategically-located reefs can serve as seedling cradles, supporting connectivity among reefs and promoting the recovery of degraded reefs," the report says.

"To maximise the conservation benefits of MPAs now and into the future, strategic planning of locations is therefore critical."