How we manage coral reefs, and how we use their ecosystem services – such as for fishing and tourism – needs to be informed by a good understanding of the threats they face. These include pollution as well as climate change, in particular coral bleaching caused by increasing temperature.
When water is too warm, corals expel the algae living in their tissues, causing the coral to turn completely white. Corals can survive a bleaching event, but bleaching often causes widespread coral death.
The longest global coral bleaching event ever recorded (2014-2017) has just ended. This devastated reefs in many areas, and science indicates that recurrent bleaching events will be the norm on many reefs by mid-century.
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A key challenge for environmental planners and managers, conservationists and policymakers is therefore determining which actions to implement, and where, to maximize coral reef resilience, protect reef biodiversity, and sustain ecosystem service provision in a changing climate.
A key challenge has been the limitation of climate models, which are too coarse to provide meaningful predictions of future bleaching.
UN Environment and its many partners, including Small Island Developing States, have recognized the need for downscaling of climate model projections to enable better projections of the future impacts on small islands, as well as the need to take urgent action to protect coral reefs and enhance their resilience.
While all reefs are vulnerable to climate change, this new approach gives us a much more detailed picture of vulnerability. It also enables identification of reefs that are likely to face frequent bleaching much later than others – “refugia” that may be priorities for conservation.
Coral Bleaching Futures describes recent work to downscale climate model projections, and findings, including a regional summary for the Pacific, elaborating on a paper published in Nature Scientific Reports earlier this year as well as the data previously made available on Environment-Live.
It notes that countries with large area of climate refugia include Australia, Indonesia, Philippines, Papua New Guinea, Bahamas, Cuba, French Polynesia (France), Japan, Egypt, Eritrea and Madagascar. Some countries in the Middle East / ROPME Sea Area have a particularly high proportion of global climate refugia, where frequent bleaching is expected to begin particularly late.
The report also provides suggestions for the use of the data, including for marine spatial planning, marine protected area network design, and in socioeconomic vulnerability assessments.
UN Environment and partners have also developed A Guide to Assessing Coral Reef Resilience for Decision Support. The Guide helps environmental planners and managers assess, map and monitor coral reef resilience, and use the results to identify and prioritize management actions that support resilience in the face of climate change.
Based on such information, naturally resilient sites can be protected, for example through marine protected areas, and appropriate policy or management action can be taken through sectors that influence reef resilience, such as fisheries and coastal development.
“These two publications provide key tools in managing reefs during climate change. I strongly encourage people to put them to use, locally, nationally and regionally,” says Isabelle Louis, Deputy Director of UN Environment’s Asia and the Pacific Office. “They also provide a valuable resource for outreach in the context of the International Year of the Reef 2018.”
For further information: Jerker Tamelander, Head of UN Environment’s Coral Reef Unit, tamelander[at]un.org