Reef State and Resilience in a Climatically Changing Environment

by Kimberly Coombs

Climate change has been impacting coral reefs all over the world, and many models have been created to predict how coral reefs are going to respond to global climate change, in particular, global warming. It has been reported that the effects of greenhouse gas emissions have reduced coral reefs resilience, causing them to be more susceptible to stressors in their environment. As a result, coral reef state, the percent of coral cover, has begun to be greatly lessened, with a noticeable shift from coral dominated environments to macroalgae environments. Continue reading

Algal Symbionts may make Corals Resistant to Rising Sea Temperatures

by Kimberly Coombs

Corals share a mutualistic relationship with algal symbionts, but with increasing sea temperatures, these symbionts become expelled from the coral. The loss of symbionts causes the corals to become bleached and there have been declines of coral cover worldwide. Recent research has shown that there may be symbionts that are thermotolerant, such as the genus Symbiodinium, which may help reduce the amount of bleaching episodes seen amongst corals. Symbiodinium is divided into nine subgeneric clades, A-I, and the Symbiodinium D1a has been documented showing thermotolerance. Continue reading

Potential Coral Reef Structure Changes from Climate Change

by Kimberly Coombs

Coral reefs vary in structural architecture, meaning that the structure can be very complex or relatively simple. The more structurally complex a coral reef is, the more species diversity may be supported. The reef building corals that create the complex coral reef structures need to have a sustainable carbonate budget in order to continue the processes of accretion and erosion to build the coral reefs. These corals have been experiencing reductions in their carbonate budget; as a result, they have declined around the world. Continue reading

Just Released! “Energy, Biology, Climate Change”

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Our newest book, published on May 6, 2015 and available at Amazon.com for $19.95.

The focus of this book is the interactions between energy, ecology, and climate change, as well as a few of the responses of humanity to these interactions. It is not a textbook, but a series of chapters discussing subtopics in which the authors were interested and wished to write about. The basic material is cutting-edge science; technical journal articles published within the last year, selected for their relevance and interest. Each author selected eight or so technical papers representing his or her view of the most interesting current research in the field, and wrote summaries of them in a journalistic style that is free of scientific jargon and understandable by lay readers. This is the sort of science writing that you might encounter in the New York Times, but concentrated in a way intended to give as broad an overview of the chapter topics as possible. None of this research will appear in textbooks for a few years, so there are not many ways that readers without access to a university library can get access to this information.

This book is intended be browsed—choose a chapter topic you like and read the individual sections in any order; each is intended to be largely stand-alone. Reading all of them will give you considerable insight into what climate scientists concerned with energy, ecology, and human effects are up to, and the challenges they face in understanding one of the most disruptive—if not very rapid—event in human history; anthropogenic climate change. The Table of Contents follows: Continue reading

The Economic Value of Coral Reefs

by Kimberly Coombs

Coral reefs are known for supporting a habitat rich in species diversity and abundance. Besides the benefit coral reefs provide to other species, they also offer a benefit to humans. Coral reefs provide a source of economic gain in terms of tourism and fisheries, usually bringing in about $30 billion each year. However, climate change is threatening to diminish this revenue as corals become bleached and experience higher rates of mortality.

Chen et al. (2015) conducted a study to estimate the global economic impact from loss of corals as a result of climate change. They identified three main factors from climate change that impact coral reefs the most: sea surface temperatures, CO2 concentrations in the water, and sea level rise. In order to assess the impact of these factors on coral reefs, Chen et al. used a threshold model in which they found that there are two temperature thresholds that may negatively impact coral reefs. When sea surface temperatures are between 22.37 and 26.85, coral cover may increase; conversely, when sea surface temperatures drop below 22.37 or rise above 26.85, coral cover decreases. Chen et al. found that increasing CO2 concentrations also cause a decrease in coral cover, while sea level fluctuations were found to have no significant effect.

In order to evaluate the value of coral reefs, Chen et al. used a meta-analysis that incorporated the percent coral cover, number of visitors to the reefs, GDP per capita, and the tourism expenditure for each visitor. They found that when coral cover decreased, reef value was reduced. The number of visitors correlates negatively with coral reef value because visitors prefer to visit uncrowded coral reefs. The GDP per capita and the tourism expenditure for each visitor were found to have positive effects on coral reef value.

Lastly, Chen et al. developed four different mitigation scenarios in response to climate change to evaluate coral reef value. The impact of these different mitigation scenarios on tourism and recreation revenue varies as coral cover varies under these scenarios. The economic loss ranges from $1.88 billion to $12.02 billion by the year 2100. Chen et al. noted that this result only represents the coral reef value from tourism and recreation and that there are many other factors that will be impacted by a decline in coral cover; therefore, they create a crude economic loss estimate under these four mitigation scenarios that ranges from $3.72 billion to $23.78 billion.

Overall, CO2 and sea surface temperatures will affect coral cover, which will reduce the coral reef value. A reduction in coral reef value reduces the recreation and tourism expenditures amongst other factors; therefore, ensuring coral cover remains high will give a higher guarantee that recreation, tourism.

Chen, P., Chen, C., Chu, L., McCarl, B., 2015. Evaluating the economic damage of climate change on global coral reefs. Global Environmental Change, 30, 12-20.

Potential for Coral Reefs to Recover after Coral Bleaching Events

by Kimberly Coombs

In 1998, a mass coral bleaching event resulted from increased water temperatures due to climate change and impacted corals world wide. This event caused much of the coral cover to be greatly reduced as many corals have a narrow set of temperature ranges that they can survive, and most live near their upper thermal maximum; therefore, slight increases in temperatures can have negative affects on coral survivorship. Not much is known about the ability of corals to recover after coral bleaching events or the likelihood of the environment switching to an algae dominated environment.

Graham et al. (2015) conducted a study in order to identify reef recovery, the amount of coral cover being greater than macroalgal cover post-disturbance, or a regime shift, the amount of macroalgal cover being greater than coral cover post-disturbance, at the Seychelles reefs. This study observed 21 reef sites from 1994 to 2011 in which about 90% of the coral cover was lost in 1998. They found that 12 of the 21 reef sites were able to recover post-disturbance, yet it took about 10 years to see any major improvements in the amount of coral cover. On the other hand, the other 9 reef sites switched to a macroalgae dominated environment. Before the mass bleaching event, the macroalgae and coral cover percent were the same between the 12 reefs and 9 reefs, suggesting that the regime shift resulted from coral bleaching. Continue reading