The Heat is On: El Niño Heralds the Future of the World’s Corals

These corals in Kealakekua Bay, Hawai'i, aren't doing so well, and in coming years, more of the world's reefs may look this way.
These corals in Kealakekua Bay, Hawai’i, aren’t doing so well, and in coming years, more of the world’s reefs may look this way.

Last January was the hottest one on record, chasing the heels of the hottest year on record. This heat is impacting our coral reefs—the lifeblood of our oceans—and despite the promises of geoengineering and local conservation efforts, there’s no quick fix for these impacts.

These shattered records result from climate change fingerprinted onto a powerful El Niño, which warms the tropical Pacific Ocean and releases an unusual amount of heat into the atmosphere. This El Niño has changed patterns of temperature, drought, and floods across the world. It’s even been linked to the spread of mosquitoes that carry the Zika virus.

But, one of the biggest and most far-reaching impacts of El Niño lurks beneath the surface of our oceans: coral bleaching.

Coral bleaching often results from extreme ocean temperatures. Tiny algae live inside the tissue of the coral itself, generating nutrients from sunlight for its host. When the coral is “stressed” by high temperatures, it expels these algae, which turns the coral bone-white. While a coral can survive this bleaching for a few months, it’s starving, deprived of nutrients provided by its algae.

A bleached coral is more prone to disease and death. For example, heating of the tropical Atlantic in 2005 led to a bleaching event that killed nearly half of the Caribbean’s corals. Reefs are the foundation for healthy marine ecosystems. For example, they provide nurseries and breeding grounds for a quarter of the ocean’s fish, so the loss of these corals can decimate marine biodiversity.

Coral bleaching impacts humans as well. Reefs attract tourists, provide livelihoods for fishermen, and form living sea walls against erosion, generating an estimated $30 billion per year.

They’re also the sole subsistence for hundreds of thousands of Pacific Islanders. In the Marshall Islands of the western Pacific, reefs provide not only food, but also supply the coral sand that forms the islands themselves. Without its reefs, the entire nation will literally disappear. Researchers on a recent ecological survey of the Marshalls discovered the worst bleaching of its corals ever seen. It’s a foreboding finding for this fragile nation.

In short, the stakes are high.

The National Oceanic and Atmospheric Administration (NOAA) uses satellite measurements of ocean temperatures to predict bleaching. In 2014, it began monitoring an outbreak that escalated to the third-ever global coral bleaching event in October 2015. Reefs from Australia to Hawai’i to Florida turned white. El Niño is worsening and prolonging this problem. In fact, NOAA scientists just announced that this bleaching event is the longest one ever observed.

In the coming decades, ocean warming will usher in frequent, longer, and more severe bleaching, increasing coral death rates worldwide. This trend has led the Australian government to declare climate change the single biggest threat to its iconic Great Barrier Reef. That assessment likely holds for reefs worldwide.

So, what can we do to conserve our corals?

First, we have to recognize that temperature is not a reef’s only stressor. Runoff, chemical pollution, and invasive species can all decrease a coral’s ability to beat the heat. Maintaining clean oceans and limiting the spread of invasive species can encourage the growth of healthy corals. That’s been the management policy for the Great Barrier Reef, and it could work elsewhere.

While these actions could buy time for our reefs, they’re stop-gap solutions at best. Any attempt to minimize global coral bleaching has to address climate change. Because carbon dioxide also acidifies our oceans, solutions that cool the planet without cutting our carbon emissions won’t spare our reefs.

The Paris Climate Agreement is a step in the right direction. Now, it’s up to each nation to fulfill its commitment. As citizens, we must hold our government accountable to its promise to curb carbon emissions. It’s easy to fall into an “out of sight, out of mind” mentality, but ignoring the issue will only worsen it.

The solution won’t be easy, but without it, the future of our coral reefs will be far less colorful.

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