What Coral Reefs Can Teach Us

On many coral reefs, the living corals have died, the reef has turned to rubble, and diverse algae have overgrown the rubble. So far, about 80% of coral cover on Caribbean reefs has been lost, and about 50% has been lost on the reefs in the tropical Pacific. Ecologists call this shift in ecosystem structure a phase shift, or ‘regime change’.

This global coral reef disaster is not a new and sudden response to some new stress. The shift to algae has been coming for 3 or 4 decades, and the stresses responsible include overfishing of both predators and herbivores, pollution, demolition, hurricanes, diseases of both corals and sea urchins, along with ocean warming and coral bleaching. Sea level rise and ocean acidification pose ever greater threats in the decades ahead.

Surviving coral reefs around Indonesia are still fished illegally with dynamite (solcomhouse.com)

Surviving coral reefs around Indonesia are still fished illegally with dynamite (solcomhouse.com)

If we could stop the fishing, the pollution, and the habitat destruction, as we do in no-take Marine Protected Areas, and assuming for the moment that the ocean is not going to get too warm, too high, or too acidic too quickly, what kind of coral reef recovery is then possible?

If herbivores like parrot fish and sea urchins return to a reef, they can clear the algae off pieces of the substrate, and coral larvae have a chance to colonize. Whether they succeed depends on many factors: light, current, predators, competition, chance, and even the ‘taste’ of the reef. But recovery is at least possible.

To help coral reefs recovery, corals are grown for a year or two and then transplanted to a damaged reef (digitaljournal.com)

To help coral reefs recovery, corals are grown for a year or two and then transplanted to a damaged reef (digitaljournal.com)

Of course we cannot pretend that climate change will not devastate coral reefs, no matter how resilient they might be now. Even under ideal conditions, recovery would take decades, and time is something we don’t have much of.

But coral reefs may still have a lot to teach us. We know now that shifts from one stable phase to another stable phase of an ecosystem can take decades, and is likely to be the result of accumulating and interacting stresses. Such a shift may start without our recognizing it for decades, and once we finally recognize it, there may then be little we can do about it. As the climate warms, we are likely to see this play out repeatedly in both marine and terrestrial ecosystems.

Can it also occur at a planetary scale, shifting us from a cool and dry planet to a hothouse planet? It has happened before. Perhaps it has already started, a result of accumulating stresses that we have caused, passing a tipping point we have not noticed.

Or perhaps we have not reached that point, and we can recover some of what we have lost, like no-take zones in MPAs. Perhaps we can still slow the process enough so that the outcome is one we and most of our co-existing species can tolerate as we too explore the limits of our resilience.

Coral reefs as we remember them (plaza.ufl.edu)

Coral reefs as we remember them (plaza.ufl.edu)

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