A reader asked after our recent Q&A about coral reefs if coral reefs were adapting to climate change by some form of migration. Is it possible for corals to move or grow in other places that are more conducive to their needs?
We asked two experts if this was possible and if migration could help save coral reefs. Stephanie Wear is a marine scientist with The Nature Conservancy’s Global Marine Team. She said that there is little evidence that this is happening:
At this point, there is little evidence that corals are migrating. For this to happen, so many factors would have to be just right in the new location. Corals require certain levels of water clarity, sunlight, nutrients, and temperature. A migration to cooler waters is just addressing one requirement corals have. Corals also grow very slowly so this kind of adaptation is not likely to happen fast enough. There is some evidence that corals are adapting by swapping out their typical zooxanthellae for more heat tolerant zooxanthellae. The research on this is new and we are hoping that the early findings spell hope for corals for the future.
Stuart Green, director of the Philippines Program for Rare said that, while possible, migration is not going to save coral reefs:
Indeed in some isolated places that were historically colder than optimum for coral reefs to grow (some isolated parts of Africa and other locations) then perhaps this is the case. But unlike fish and other more mobile organisms, corals can only migrate through reproduction and currents. Corals are fixed to the reef. So although there are small areas that may benefit, the majority of the worlds reefs will be dying or severely stressed by the changing temperatures and other impacts of climate change.
Corals settle once and cannot move. Their only way to repopulate other areas is through passively moving through current. A coral larvae chooses to settle favorable substrates using cues: environmentally sound (i.e. intact/solid substrates), mother colonies present, and healthy reefs are favored. A decimated coral reef — due to impacts other than climate change — is unlikely to receive seeds or self seed.
Coral bleaching events have been increasing in both frequency and extent, and it looks like the current bleaching that is taking place at the moment could be the most significant ever.
Rare believes in Marine Protected Areas with no-take zones to bolster Coral Reef Resilience. We are working in the Coral Triangle to set up MPAs.