EXPERT REACTION: Is the reef resilient enough to regenerate?

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 fertilized 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.

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.