Since the devastating coral bleaching event in 1998, scientists and managers have been working hard to understand why coral reefs have varying abilities to recover from bleaching. Now, reef managers have a powerful tool to predict which reefs are likely to recover, thanks to new research published yesterday in the journal Nature.
I talked with coral expert Stephanie Wear to discuss this breakthrough research. Wear is the lead scientist, spokesperson and NatureNet Science Fellow for coral reef conservation at The Nature Conservancy. She specializes in developing new strategies to reduce threats to coral reefs.
Q: Do we know why some reefs survive bleaching and others don’t?
In 1998 there was a devastating bleaching event — the biggest event that the world has seen yet. Up to 90 percent of the reefs in the Seychelles, where this study was conducted, died as a result. Across the tropics, some reefs survived, some died, and others didn’t bleach at all. Since then, scientists have been trying to figure out why coral reefs respond differently, and what characteristics make them resilient. This is really important for conservationists trying to figure out how they should focus their conservation and management efforts.
We’ve learned that fish play a really important role in the reef, especially herbivorous fish that eat seaweed. We also know that it’s important to have good water quality for a reef to recover. And we know that having space for baby corals is critical to support long-term recovery on a reef.
Q: So what does this paper reveal about recovery?
What this particular paper does that’s so important is point out four factors that predict which reefs will recover, with great accuracy. And two of these factors — water depth and structural complexity — are easily and cheaply identifiable by somebody managing a reef. One of the biggest challenges that reef conservationists face is where to invest their limited resources — they have to make difficult choices. What this study does is provide a big leap forward by identifying factors that are easy to measure that can be used to predict recovery.
Q: What does a structurally complex reef look like?
A structurally complex reef is like a mountain, with lots of nooks, crannies, caves, holes, and pathways going through it — a rugged-looking mountain. A structurally complex reef has lots of space and surface, with variations in the shape of the reef — bumpy, lumpy, sharp or jagged, with overhangs, cliffs, and lots of different variety. All of that variety creates habitat for creatures on the reef, from tiny crabs to big grouper. A less complex system is like a flat plain with some rolling hills, but no nooks and crannies or places to hide and avoid a predator. Structurally complex reefs are more productive and they’re generally more diverse, simply because there’s more space.
Q: So were these results surprising?
Not exactly. There are many factors that have been proposed or identified as being important for reef health. What is surprising is how accurate the factors identified in this study are in predicting recovery to a major bleaching event. The study found that, when combined, water depth and structural complexity predicted recovery 98 percent of the time. It’s insane to have that level of predictive power. That’s what’s surprising, and I think that is what’s going to make this research very useful to coral reef practitioners. This paper gives reef managers an easily measurable tool that can be used to predict recovery and resilience.
Q: Can these findings be applied to reefs elsewhere, outside of the Seychelles?
That’s the big question. The results of this study are pretty powerful, and the study design was ideal, because they had solid before and after data for a major bleaching event, which is pretty unusual. What happens next is that scientists studying other regions will be looking to see if these factors can also predict reef trajectory in other parts of the world. It’s hard to know how broadly these findings can be applied, but I think it’s likely that they will be applicable beyond the Seychelles.
Q: Is The Nature Conservancy going to do anything differently based on the findings of this paper?
At the Conservancy, we work quickly to get the latest science into the hands of the people that need it most, the people that are tasked with managing coral reefs and protecting natural resources around the world. The first thing we’ll do is share this paper with our Reef Resilience Network, our global network of coral reef practitioners in more than 75 countries. Since this is a really important new finding, we will adapt our recommendations to coral reef practitioners to incorporate these results.
Q: Will this research change the way conservationists protect and manage coral reefs?
I imagine that this paper will be very helpful to coral reef practitioners. With two simple factors that require very little under-water study and monitoring, reef practitioners are going to be able to better prioritize their efforts. In a world where resources are limited and prioritization is key — it is going to make a big difference.