Could the Great Barrier Reef regenerate?

  Last updated December 1, 2017 at 5:08 pm

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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.


Colorful underwater scene of a tropical reef and fish. Go pro camera shot


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 coral-eating pest, the crown-of-thorns starfish, and crosschecked that list against the first to come up with a ‘robust’ 3 per cent of reefs.


The authors of the PLOS Biology paper say these 100 reefs could help desirable species recover – suggesting a level of wide-spread 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 AusSMC.


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, of many of the species of animals living on the Great Barrier Reef, it’s likely many of them would 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 2300km 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.”


What experts say


Dr Andrew Lenton – Principal Research Scientist at CSIRO Oceans and Atmosphere and is from the Centre for Southern Hemisphere Oceans Research, and Antarctic Climate and Ecosystems CRC


“This new study highlights the biological richness and complexity of the Great Barrier Reef (GBR), which is under threat from a range of factors including climate change, water quality, coastal development and fishing.


“The GBR has been significantly impacted over the last two summers, with up to 50 per cent coral mortality occurring in the Northern GBR; and while this has been very significant, corals do have a capacity to recover from such events.


“This new and exciting research identifies the factors that need to be in place to maximise the capacity of corals to recover from such environmental stresses. In this study scientists bring together multiple datasets, collected over more than 3 decades, to identify those reefs which have both experienced lower environmental stresses and play a critical role in supplying fertilised larvae to other reefs.


“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; and this paper highlights the importance of protecting and managing these refugia.


“However, it also recognises that this alone is not likely to be sufficient to ensure the longer-term viability of the Great Barrier as a whole; and will need to be coupled with climate mitigation, local management and active management such as coral re-seeding.”


Associate Professor John Alroy – the Department of Biological Sciences in the Faculty of Science and Engineering at Macquarie University


“This new paper is really thorough and interesting. It brings together several very different kinds of information with sophisticated modelling, and I think it makes a good case that corals will persist for a while on a fair number of reefs. But I think it’s optimistic.


“First off, the paper shows that almost all of the reefs most likely to survive are concentrated in the southernmost one-third of the GBR. That makes me wonder whether reefs in the far north can really be kept alive by being replenished from the south.


“Second, there are so many species of animals living on the GBR –including some 1500 species of fishes – that many of them must be absent from the ‘robust reefs’. Some of those species may already be gone, and others won’t last long.


“Third, 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.”


This article was first published by the Australian Science Media Centre and is reprinted here with permission.



About the Author

Anna Kosmynina

Anna Kosmynina is a media officer at the Australian Science Media Centre.


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