Teaming with life, coral reefs are some of the most diverse ecosystems on earth. Countless numbers of marine species depend on these reefs, and humans do as well. With so much dependent on the tiny animals that construct these reefs, scientists are trying to understand environmental factors that may affect the complex relationship between these marine ecosystems and the people who depend on them.
Linwood Pendleton is the international chair of marine ecosystem services at the European Institute of Marine Science and senior scholar of Duke University’s Nicholas Institute for Environmental Policy Solutions. He has always been fascinated with the intertwined relationship between marine ecosystems and people. To unlock this relationship, Pendleton has focused on understanding the impact of global environmental stressors on reefs and human populations.
Rising carbon dioxide levels amplify the risk of elevated sea surface temperatures and ocean acidification, and these two global stressors may severely harm warm-water coral reef ecosystems and the people who depend on them. In his most recent study, Pendleton and his team used an indicator approach to identify where coral reef-dependent people were most likely to be affected by rising CO2 levels by 2050. They scored and mapped the two indicators of CO2-driven coral reef stress – ocean acidification and rising sea surface temperatures – along with two indicators of human dependence on coral reefs.
Combining these maps of indicator scores revealed that most of the world’s coral reefs will likely be affected by either warmer seas or more acidic oceans, with coastal communities in Western Mexico, Indonesia, parts of Australia and Southeast Asia being the most impacted.
To tell us more about his study, Pendleton agreed to answer a few of my questions by email.
Let’s start off with a bit of background. What made you interested in pursuing work focused on environmental policy and coral reef ecosystems?
LP: As a doctoral student in the 1990s, I began studying the way people use and depend on coral reefs. One of my fellow students from those days, Lisa Suatoni, approached me four years ago and asked me how I would scientifically identify what places and which people might be harmed by ocean acidification (OA).This led us to work with Dr. Sarah Cooley, then at the Woods Hole Oceanographic Institution, to apply for a Venture Research Project at the National Social Environmental Synthesis Center. We got that grant, and it allowed us to assemble an interdisciplinary team to look at the effects of OA on both shellfish in the U.S. and corals worldwide. Because of my experience working with coral reef social-ecological systems, I led the coral team.
In your recent study, you used an indicator approach to identify where key environmental factors driven by high CO2 levels may put coral reef-dependent people at risk. Why did you choose this approach, and how does it allow you to understand characteristics of a social-ecological system?
LP: One of the most challenging aspects of interdisciplinary research, especially on socio-ecological systems, is managing complicatedness and complexity. Scientists have the tools to create extremely complicated models, but additional complexity does not always make for better applied research. Sometimes the science is not there to support this increased complexity. Furthermore, it can be difficult to explain your science when it is overly complex. Our goal was to create an analysis that was scientifically rigorous and would inform policy. We have science about many of the important elements that link climate change, OA, coral reefs and people, but not enough for a reasonable model of the whole system. An indicator approach allowed us to focus our analysis on settled science, without having to create complex and complicated models that may have been filled with uncertainty. In the end, we have an analysis that is understandable, transparent and yields clear conclusions that are substantive but not over-reaching.
Elevated sea surface temperature and ocean acidification were the two key global environmental stressors you researched. Why focus on these?
LP: We focused on these two stresses because they were largely out of the control of local coral reef communities and managers. We wanted to show where “exogenous” stresses were likely to create serious ecological and human challenges for people that depend on coral reefs. At the same time, we pushed to have our research published in time for the COP 22 U.N. climate meetings. Part of the responsibility of the carbon emitting nations, through the Green Climate Fund, is to help offset the inevitable impacts of climate change. Our research helps to identify those places that will be harmed by the effects of climate change and OA on coral reefs.
You mention that most of the countries in the study that are the most dependent on coral reefs also have the least robust data on ocean acidification. How did you overcome this limitation in data availability to find out which coastal communities are most threatened?
LP: We have reasonably good data on human dependence on coral reefs and projected sea surface temperature for most countries. This helps us identify whether these countries have the preconditions to be among the places most impacted by the combined effects of climate change and OA. Then we used the best available data and projections on OA to show what the current science says about the risks these countries face. Clearly, if a country has high human dependence and a projected future threat from sea surface temperature, it is in its best interest to do all it can to understand whether it will also face a threat from future ocean acidification.
Now that you have identified countries most at risk, such as Mexico, Indonesia and parts of Australia, what can these countries do to protect their coral reefs and communities?
LP: Many of the big countries we identified as “at risk,” like Indonesia and Australia, are also major carbon emitters. They could begin by reducing carbon emissions. Otherwise, countries need to take immediate action to reduce local environmental factors that make the combined stresses of coral bleaching and OA even worse – overfishing and damaging fishing practices, pollution, eutrophication, coral mining and destruction.
What’s next for your research? Where would you like to go from here?
LP: We are now drilling down to understand how these threats, and the ecological context of specific coral-reef communities, affects the ways people in French Polynesia deal with changing reef conditions.
Research Article: Pendleton L, Comte A, Langdon C, Ekstrom JA, Cooley SR, Suatoni L, et al. (2016) Coral Reefs and People in a High-CO2 World: Where Can Science Make a Difference to People? PLoS ONE 11(11): e0164699
Image Credits: Expl0601 Coral (Montastrea cavernosa) by NOAA via Flickr, Dr. Linwood Pendleton profile shot, Fig 1. A conceptual diagram linking stresses related to increased atmospheric CO2 by Pendleton et al.