Coral Bleaching and Climate Change

Coral Bleaching and Climate Change

• Coral bleaching is becoming more common due to increasingly severe and frequent marine heatwaves.
• Four global mass bleaching events have occurred since 1998, with two happening in the past decade.
• Unless greenhouse gas emissions are reduced, coral bleaching will start in spring rather than late summer by 2080.

Impact of Marine Heatwaves

• Marine heatwaves stress corals, causing them to expel symbiotic algae and turn white and weakened.
• Prolonged heat stress harms coral health and reproduction.
• Coral reefs cover only 1% of the oceans but host at least 25% of all marine species.

Importance of Coral Reefs

• More than half a billion people worldwide depend on coral reefs for food.
• Coral reefs are vital for the health of the ocean and people.
• They are also among the ecosystems most at risk from climate change.

Predicting Coral Bleaching Risk

• Recent improvements in climate modeling allow for predicting coral bleaching risks with high accuracy.
• Daily projections of heat stress from global climate models show the severity and duration of coral bleaching will soon reach uncharted territory.

Region-Specific Risks

• The greatest risk of coral bleaching is along the equator, where the most biodiverse coral reefs are found.
• Equatorial regions are home to conservation hotspots such as the Coral Triangle.
• Many equatorial species are already living at temperatures near their upper tolerance and have low abilities to move to track shifting climates.

Impact on Coral Spawning

• By 2040, coral spawning events could coincide with severe bleaching risk, reducing reproductive success and causing large-scale coral loss.

Identifying Lower-Risk Regions

• Regions such as the northern coasts of Venezuela and Colombia, Socotra Island, and Alor Kecil in Indonesia are predicted to have lower risks of coral bleaching due to seasonal upwellings.
• Identifying these regions can help conservation managers and policymakers prioritize efforts to limit loss of coral reef biodiversity.

Conservation Strategies

• Curbing greenhouse gas emissions is the main solution to reduce future climate impacts on corals.
• Other strategies such as assisted evolution, coral restoration, or transplantation can help maintain healthy coral populations at local scales.
• A user-friendly web-based tool for mapping future coral bleaching can help pinpoint locations for effective management interventions.