Large-scale protection could be the key to saving reefs

By Danielle Moloney 

Edited by Sofia Perez


Millions of people around the globe rely on coral reefs for food, income, recreation, and a host of other services (including protection from storms and erosion along coastlines). Reefs are under heightened stress around the globe due to increasing global temperatures, a significant driver in both coral bleaching as well as mortality. Carbon emissions play a significant role in increasing temperatures and carbon emission reductions would greatly benefit the outlook for reefs. As climate change and other anthropogenically influenced factors continue to batter sensitive coral reefs, environmentalists strive to prevent and undo damage by conserving these natural ecosystems. For decades, scientists have called for actions that will protect reefs from their fastest growing threat, climate change. Conservation strategies often focus on increasing both coral growth and coral cover, but environmental policy decisions can also significantly impact reef survival. A recent paper by van Woesik et. al assessed how corals across many biological scales respond to stress. They found that international marine sanctuaries may spell success for the future of reefs. 


In order to test many scales of coral responses, van Woesik et. al chose several factors that contribute to reef health and wellbeing- such as environmental drivers of bleaching, thermal tolerance, and responses to bleaching- to make a wide range prediction about how reefs may best be conserved. This included data from many scientific publications as well as some long-term global reef assessments. They also included a variety of sampling methods in their research in order to address different biological/ecological scales. Furthermore, they used literature reviews to determine current trends in conservation successes. 

Figure 1. A global map depicting coral bleaching (as a percent bleached out of total coral colonies) between 1980 and 2020. (Figure courtesy of van Woesik et. al 2022). 
Figure 2. A diagram showing the different tools that can be used to assess a reef at various biological-scale levels. Here, the authors address how they were able to synthesize data from diverse sampling tools in order to determine their wide scale findings for reef success in the future. (Figure courtesy of van Woesik et. al 2022). 

What did they find? 

Many insights were garnered from this research, including steps that the scientific and conservation communities can take to aid ailing reefs in the coming years. One of the main takeaways that van Woesik et. al drive home is the need for mesoscale (very large scale) marine sanctuaries. This type of sanctuary spans thousands of kilometers and likely passes through international borders. Though the researchers highlight many of the gaps in our knowledge that are still needed, such as spatial variability of thermal tolerance or a better understanding of post-bleaching recovery, they feel that large marine sanctuaries may ameliorate some of the pressing stressors that reefs face today. One of the draws of these large sanctuaries is that they help conserve reef behaviors that span spatial boundaries, such as larval settlement. To reproduce, corals release egg and sperm cells into the water column. These cells join together and form an embryo known as a larva. In order to begin to grow, these free-floating larvae need to find a place to “settle”, or attach to a surface, where they will become immobile and live the rest of their life in that exact spot. They note that this is one of the factors that should be considered when forming these sanctuaries. Allowing for proper larval dispersal (in other words, that the larvae settle in a location with optimized conditions for growth and survival) increases the genetic variability of a population, which in turn makes it more resilient to stress events. Mesoscale sanctuaries also address the need to protect both reef habitat and diversity by spanning wide areas, up to thousands of kilometers of ocean space, and both of these components are important to the future success of coral reefs. 

A possible barrier to implementation of these mesocosm scale sanctuaries is the need for international cooperation that transcends borders. There is currently little coordination between different countries when it comes to reef conservation efforts, though this is contrary to the interconnected nature of coral reef environments. Often, higher income countries conduct research in lower income nations where reefs are abundant. Without engaging local communities with vast knowledge of their own homes, the scientific community as a whole misses out on important opportunities for progress and equity. In addition, there has been a historic disconnect between scientists who conduct research and policy makers who decide how research findings are translated into action. Strengthened connections between these two entities would increase success of mesoscale sanctuaries by ensuring that research is accurately incorporated into decisions about size, location, regulations, and other governing factors of marine sanctuaries. The authors suggest not only an increase in reef conservation efforts within counties, but also augmented international efforts that would support the implementation of mesoscale sanctuaries. 


A small number of mesoscale marine sanctuaries already exist, but more are needed in order to affect change. While the global population struggles to reign in carbon emissions, an optimistic alternative is the use of environmental policy decisions such as large sanctuaries to address reef stressors now. Reducing carbon emissions is a timely endeavor, and while implementation of sanctuaries is not instantaneous, it may be a speedier alternative. Ultimately, significant action is needed on many levels, from local to international, and research-based to policy-based, in order to expect a positive outlook for reefs in the future. Though global reef health continues to decline, important research continues to highlight paths forward that can save some of the diversity and prosperity of coral reefs.

Read the full study from van Woesik here

Please contact the author with any questions:

Cover Photo courtesy of Allen Coral Atlas.

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