Three of Four Parts
Bleaching is not always fatal for corals. If water temperatures cool quickly enough the animals can recover.
The problem: bleachings are lasting longer and coming in rapid-fire succession. This year’s is the fourth since 1998 and second in the last decade. It follows a devastating bleaching that stretched from 2014 to 2017 that left about 9 percent of the world’s corals dead.
Repeated bleaching has contributed to an unmistakeable trend: corals are disappearing. Between 2009 and 2018, the world lost 14 percent of its coral cover, according to a 2020 study from the Global Coral Reef Monitoring Network, which is supported by UNEP.
It remains to be seen just how deadly this year’s bleaching will be. But a large-scale die-off would have far-reaching consequences for sea life and humans. Corals underpin coastal fisheries, which support 1 billion people.
The long-term outlook for most warm water corals is grim. Humanity continues to churn out the greenhouse gases that have warmed the planet about 1.2°C since pre-industrial times. The vast majority of that heat is being swallowed by the ocean.
In recent years, four key climate change indicators–greenhouse gas concentrations, sea level rise, ocean heat and ocean acidification–set new records.
Even if the world manages to reach the most ambitious goal of the Paris Agreement on climate change –limiting global temperature rise to 1.5°C–70 percent to 90 percent of reef-building corals are expected to die. If temperatures rise 2°C, 99 percent will perish.
Researchers have found pockets of water off the coasts of Australia, Egypt, Indonesia, Kenya, Malaysia Saudi Arabia, Tanzania and where corals are resisting the ravages of climate change. In some of these safe havens, known as refugia, the upwelling of cold water from the ocean depths is keeping corals cool. In others, corals themselves have a higher tolerance for heat.
Conservationists are focused on protecting refugia and other coral hotspots from stressors like pollution, over-fishing and coastal development. The hope: give corals the best chance possible to survive climate change. (To be continued)
