As global warming devastates coral reefs, a controversial proposal to replace native coral species with heat-resistant ones from other regions is stirring debate. 

New York University’s Michael Webster and the University of Washington’s Daniel Schindler argue that “ecological replacement” may be essential for preserving reef ecosystems.

While this approach raises concerns, its supporters believe it might be the only realistic solution as ocean temperatures continue to rise.

The promise of “ecological replacement”

Coral reefs are crucial for supporting marine biodiversity, shielding coastlines, and producing sand for beaches. However, as oceans warm, mass coral bleaching is killing reefs around the world. Bleaching forces corals to expel the algae living within their tissues, losing vital nutrients and often resulting in coral death.

Traditional restoration efforts, such as replanting native coral fragments, have had limited success. Hence, Webster and Schindler propose introducing heat-tolerant coral species from warmer regions that could survive higher temperatures. 

This idea, though extreme, offers hope for areas where native species struggle to survive. For instance, branching corals in the Caribbean are in serious decline, but similar species from other parts of the world could be introduced to sustain these ecosystems. 

“They’re not going to necessarily be the same colour or anything like that,” said Webster, “but they’re similar, ecologically.”

Serious risks and criticisms

Despite its potential, this proposal has stirred concerns among scientists and conservationists. Introducing non-native species could lead to unforeseen problems, such as disease outbreaks or competition with local species. 

In the 1980s, a disease near the Panama Canal wiped out algae-eating sea urchins in the Caribbean, leading to uncontrolled algae growth that killed many corals. Critics fear similar disruptions if alien corals are introduced.

Additionally, non-native corals could hybridise with or outcompete local species, causing shifts in the ecosystem that might have lasting consequences. 

Professor Terry Hughes of James Cook University in Queensland, Australia, calls the concept of “ecological replacement” naïve and dangerous, noting that previous introductions of non-native species have often resulted in severe ecological damage. 

“The authors fail to acknowledge the huge ecological damage already inflicted by accidental and deliberate introductions of exotic species,” Hughes warns.

Exploring other approaches

While “ecological replacement” is divisive, it is only one among many ideas being explored. Some scientists advocate for genetically engineering native corals to withstand higher temperatures. Others focus on selective breeding, a slower approach that could eventually yield more resilient coral populations. 

However, these methods are still experimental and costly, and it is uncertain if they can be implemented quickly enough to match the rate of coral loss.

Webster and Schindler argue that, for now, relying on existing coral diversity may be more practical than genetic interventions. “Our best bet for coral reefs is the existing diversity that’s out there,” says Webster, suggesting that heat-tolerant corals already adapted to warmer waters may be the key to preserving reefs.

A complex decision

With coral reefs in decline, conservationists face a challenging choice: take a risk with “ecological replacement” or wait for other methods that might not deliver results soon enough. Proponents stress the urgency, while critics warn of unintended ecological consequences.

This debate raises critical questions for the future of coral reefs and how best to preserve them. As scientists continue to seek sustainable solutions, the prospect of introducing heat-tolerant corals remains both hopeful and fraught, underscoring the complexity of conserving these vital ecosystems in a warming world.