Most coral reefs in the Atlantic are headed for collapse

The coral reefs in the western Atlantic are in serious trouble. Scientists now say that most of these reefs are not just slowing down their growth – they’re starting to erode.

If the planet warms by just 2 degrees Celsius (3.6°F) above pre-industrial levels, which is likely this century if emissions don’t drop fast, nearly every coral reef in this part of the world could stop growing altogether. Some will actually shrink.

A study based on 400 reef sites around Florida, Mexico, and Bonaire found that more than 70% of the region’s reefs will stop growing by 2040. By 2100, over 99% will be affected if global temperatures keep rising.

When coral reefs can’t keep up

Coral reefs grow when the organisms that build them, mainly hard corals, are healthy and multiplying. But reefs aren’t invincible.

When water gets too warm or polluted, corals bleach – they lose the algae they rely on for food – and many die. Coral disease and declining water quality also weaken reef systems.

In the Atlantic, this damage has already shifted which corals are surviving. The key reef-building species are becoming rare, and what’s left often can’t keep up. Fewer corals means less growth, and that leaves reefs falling behind rising sea levels.

The researchers combined data from fossil reefs with current ecological data from hundreds of modern reef sites.

They looked at how different types of coral contribute to reef building and used that to figure out how fast today’s reefs are growing – and how that will change if the climate keeps warming.

Coral reefs sink as seas rise

“Under current CO2 emission scenarios most Atlantic coral reefs will not only stop growing but many will actually be eroding by mid-century,” said Professor Chris Perry from the University of Exeter.

“At the same time, rates of sea-level rise will increase – and our analysis suggests the growth of reefs will lag behind.”

That mismatch could lead to an average of 2.3 feet of additional water above reefs by 2100 if global warming reaches 2°C – and up to 4 feet if it gets worse. For coastal communities, that means greater risk of flooding, erosion, and habitat loss.

Coral diversity is collapsing

The types of coral that make up a reef matter just as much as how many are there. Some species are better builders than others. But high temperatures and disease outbreaks are hitting those key species the hardest.

“We are witnessing an alarming decline in both the abundance and diversity of corals across Atlantic coral reefs,” said Dr. Lorenzo Alvarez-Filip from the Universidad Nacional Autonoma de México.

“Climate change is not only accelerating this decline but also worsening the cascading ecological and socio-economic consequences of their loss.”

It’s not just about the reefs themselves. Seagrass beds, fish nurseries, and entire marine ecosystems that depend on reefs are at risk. And people who rely on tourism, fisheries, and shoreline protection will feel the impacts too.

Can restoration save Atlantic corals?

There is some hope. Coral restoration is one strategy scientists and conservationists are using to try to bring reefs back. This includes growing corals in nurseries and transplanting them to damaged areas. But the scale of the problem is massive.

“The scale of action required to reverse current coral losses is significant,” said Dr. Alice Webb from the University of Exeter.

“To have meaningful effects on limiting water depth increases, any restoration will need to occur in tandem with effective land and water management, and rapid climate mitigation actions. Actions to keep warming below 2°C are critical.”

In other words, local restoration can help, but it won’t be enough without global action to cut emissions.

What happens if we don’t act?

If nothing changes, the natural relationship between coral reef growth and sea-level rise is going to break down. That has consequences we can’t ignore.

“We are moving into a period where the two factors that control water depths above coral reefs – vertical reef growth rate and sea level rise rate – are starting to operate in increasingly divergent directions,” said Professor Perry.

“Limiting climate warming is critical if we are to try to mitigate this and to avoid the worst impacts for coastlines and coastal ecosystems.”

The full study was published in the journal Nature.

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