By Danielle Moloney
Edited by Sara Gagliardi
In the past, reef resilience has been thought to be (in part) linked to remoteness. In other words, the farther from human activities a reef is located, the better the reef is thought to recover after disturbances. This hypothesis stems from the idea that when reefs are not exposed to local stressors such as fishing and pollution, they are more able to devote themselves to surviving global stressors, such as climate change. A recent study (Baumann et. al 2021) examined the relationship between a reef’s proximity to human activity and its ability to recover from disturbances- and surprisingly found no correlation.
The researchers used a variety of characteristics to measure disturbances from climate change, including bleaching, storm damage, disease outbreaks, and increased predation. Armed with these measures, the authors set out to examine previously published data showing changes in scleractinian coral coverage following wide-scale disturbances. Scleractinian corals (hard, reef-building corals) were used as the research subject because they often live near their thermal limit, suggesting that if temperatures increase much more, they will deteriorate and widespread mortality may be observed. Data analysis was performed on studies that met a list of criteria for their own research in order to determine whether reefs located near human activity were more or less resilient to disturbances.
What did they find?
The results of this study concluded that reefs were not more resilient if they were isolated from human activity, but in fact just the opposite. Reefs living near human impacts were somewhat more resilient to disturbance than isolated reefs. Some scientists hoped that remote reefs would survive the drastic temperature changes predicted in the coming decades, and be able to serve as a source of repopulation for other destroyed reefs in the future. However, if remote reefs are equally threatened by climate change, this avenue for conservation is much less likely to be a possibility. Overall, these results suggest that climate change needs to be stopped in its tracks in order for reefs to survive in the future.
On the bright side, the researchers noted that some reefs living close to human disturbances may in fact be quicker to recover from stress. As the human population continues to grow and invade the few remaining remote corners of the planet, more and more reefs are exposed to anthropogenic disturbances. One theory as to why these highly impacted reefs may be more resilient is that it’s possible that they have been selected for over time in the past during prior disturbance events, ending with an overall more resilient reef each time a disturbance occurs and the less resilient corals die off. Since isolated reefs are not exposed to as many disturbances, it may take them longer to select for more tolerant corals, and that may explain the finding that they are generally less resilient to stress.
The findings of this research have important implications for how coral reef conservation should proceed in the coming years and decades. While some may have planned to rely on isolated reefs to repopulate following die off events in high impacted areas, this plan is unlikely to succeed considering the sensitivity of isolated reefs to stress events. The authors end with a call to action and a warning- if greenhouse gas emissions are not reduced imminently, corals will not survive in the future. If the preservation of biologically important ecosystems is not enough of a reason to invest in conservation, wide-scale death of reefs will have an economic toll, including reduction in food availability, income, and coastal protection. The onus is on humanity to change our behavior if we want to preserve reefs; continuing on with business as usual and expecting reefs to keep up will not be an option.
All hope is not lost- a recent study showed that some corals can adapt in time to keep up with current rates of climate change. Furthermore, we can all do our parts individually to reduce our impact on the environment and help protect reefs. With effective actions, the future trajectory for coral reefs can be bright.
Read the full study from Baumann et. al here.
Featured Photo courtesy of CNN.
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