Can the Great Barrier Reef regenerate?

The Great Barrier Reef’s health could be boosted by just 3 per cent of its reefs, according to an Australian-led study.

The authors found around 100 reefs that should have healthy adult corals, and be well connected enough to supply larvae to almost half of the Great Barrier Reef in a single year.

By simulating the dispersal of larvae, the researchers could pinpoint which smaller reefs were best connected by ocean currents to the rest of the Great Barrier Reef and could top it up.

They then used ocean and climate system models to show which reefs were less likely to be exposed to coral bleaching and the crown-of-thorns starfish – a pest that eats coral – and crosschecked that list against the first to come up with a ‘robust’ 3% of reefs.

The authors of the PLOS Biology paper say these 100 reefs could help desirable species recover – suggesting a level of widespread resilience for the Great Barrier Reef – and that these reefs are unlikely to spread crown-of-thorns starfish.

“Finding these 100 reefs is a little like revealing the cardiovascular system of the Great Barrier Reef,” explained study author Professor Peter Mumby of the University of Queensland.

“These refugia are critical as they maintain the healthy populations and diversity required to rebuild coral populations, and have the ability to repopulate other reefs,” Dr Andrew Lenton of CSIRO Oceans and Atmosphere told the Australian Science Media Centre.

However, there’s reason to be sceptical, according to Associate Professor John Alroy of Macquarie University: “I think [the paper] makes a good case that corals will persist for a while on a fair number of reefs. But I think it’s optimistic.”

Given the paper shows most of the robust reefs are in the south, Alroy said it made him wonder “whether reefs in the far north can really be kept alive by being replenished from the south.”

He also pointed out that many of the species of animals living on the Great Barrier Reef are likely to be absent from the ‘robust’ reefs.

Dr Karlo Hock, of the University of Queensland and also an author of the paper, suggested more does need to be done at different scales to rescue the reef.

“Identifying only 100 reefs with this potential across the length of the entire 2300 km Great Barrier Reef emphasises the need for effective local protection of critical locations, and carbon emission reductions to support this ecosystem,” Hock said.

Lenton explained that just protecting these robust reefs likely isn’t enough to ensure the long-term survival of the whole Great Barrier Reef.

“[This] will need to be coupled with climate mitigation, local management and active management such as coral re-seeding,” he suggested.

However, Alroy warned “the paper doesn’t really address the fact that global warming is just going to get worse and worse over the next few decades and centuries.”

“So, even the ‘robust reefs’ might be wiped out in the not-too-distant future – unless we really get serious right now about mitigating global warming.” 

Prepared by the Australian Science Media Centre and used here with permission.