In the news this week . . .

A report published this week by the World Resources Initiative has caught the attention of news agencies around the world. Reefs at Risk Revisited (Burke et al, 2011) updates a 1998 report which assessed the main threats to the global coral reef resource. This time the study includes climate related threats, which contribute to the mounting pressures on coral reefs. The report estimates that 75% of coral reefs are currently at high to critical threat levels, a figure that could exceed 90% by 2030.  The Reefs at Risk research initiative aims to advance understanding regarding the spatial distribution of threats to coral reefs worldwide, providing essential information for the development of conservation strategies. 




The Encyclopaedia of Modern Coral Reefs; Structure, Form and Process will be launched today at the James Cook University in Townsville, Australia. The encyclopaedia is an extensive collection of knowledge regarding coral reefs and weighs four kilos! 




A research expedition investigating coral reefs in Semporna, Malaysia has claimed to have found the most biologically diverse coral reef in the world. 43 species of mushroom corals, which act as a proxy for species richness, were identified (the previous record was 40) as well as 844 species of fish. This study indicates the biological wealth of coral reefs and proves that some coral reef ecosystems are still in fantastic condition. Hopefully papers like this will inspire conservation initiatives and help to preserve this globally important marine resource.

Overview of Coral Reefs and the Threats Posed by a Changing Climate

Coral reefs have a high ecological importance, due to their biodiversity and the provision of a wide range of ecosystem services that are required by humans. They are often referred to as the 'Rainforests of the Sea', home to around 25% of marine species, while occupying only 1% of the ocean floor (Mulhall, 2009). Benefits to humans include: the provision of fish; coastal protection from storms; the potential successful tourism industry; source of medicines. These ecosystem services are under threat from a combination of stressors that stem from both human exploitation and anthropogenic climate change.



The formation of corals is best explained by this informative video:



The threats to coral reefs from climate change result from a combination of stresses including: increasing sea surface temperatures; sea level rise; ocean acidification due to increased atmospheric carbon dioxide concentration; changing salinity; altered ocean currents; more intense storms through ENSO variation. The impact of ENSO variation has been highlighted by recent tropical storms in north-east Australia, causing damage and sedimentation. The vast size of this cyclone is portrayed here, indicating the area of reef that was affected.



Over the next few weeks each of these threats will be discussed in detail, they are outlined in this video featuring Ove Hoegh-Guldberg, whose paper was discussed in the post below and who runs a blog that contains a wealth of information regarding climate change:

Understanding and predicting the impacts of climate change is a necessity in order to mitigate the impacts and attempt to preserve these important resources. Dr Barrie Pittock’s 1999 paper attempts to estimate changes to the environmental factors that affect coral reef ecosystems. Predicted changes include a 2-3°C increase in sea surface temperatures by the end of this century, sea level rise at a rate of 1-10mm per year and tropical cyclone intensity is expected to increase by 10-20% by 2070. These changes must then be translated into direct ecosystem consequences, such as potential species extinction. A recent attempt at predicting coral reef fish vulnerability from multiple stressors (including both climate driven habitat loss and the effects of fishing) was undertaken by Graham et al (2011). This study predicts that around a third of all coral reef fish species in the Indian Ocean are at risk from localised extinctions. Interestingly those species most at risk from one factor are not vulnerable to the other. This is worrying, as areas where both stressors are present will suffer greatly.

Figure 1  Vulnerability of coral reef fish species to fishing and climate driven habitat disturbances in Indian Ocean (Source: Graham et al, 2011). 




It is evident that anthropogenic climate change affects coral reef ecosystems significantly, through a variety of stressors. In order to be able to mitigate the impacts of a changing climate on coral reefs, preserving their biodiveristy and the provision of vital ecosystem services, the effective modelling of future changes is required.

Climate Change and Coral Reefs: An Introduction

This blog will attempt to cover the main impacts of a changing climate on coral reefs, through a discussion of key academic papers and a look at issues that hit the headlines and social media. Whilst many would perceive climate change to be a contemporary issue, coral reefs have been affected by the impact of a changing climate throughout their history. Not only does this allow the investigation of past changes to sea surface temperatures and sea levels, but will enable the simulation of future changes.

My own experience of coral reefs is fairly classic of anyone who has been to Australia! In the time I was there I spent the odd day snorkelling off the coast of Queensland, exploring reefs by boat on organised trips and under my own steam at the many islands scattered across the Great Barrier Reef. Although I'm told the best reefs are far out to sea, and many are protected from the likes of people on their gap year, the areas I went to were fairly disappointing. Especially having seen other traveller's photos of the Ningaloo Reef in Western Australia, where the coral seemed to incorporate every colour of the rainbow, reef sharks and loggerheads were plentiful and shoals of fish were vast. It appeared evident that the dual blow being dealt to these fragile ecosystems by tourism and, more significantly, climate change was having a severe impact.

Ove Hoegh-Guldberg's (1999) paper is a good place to start, as it considers the primary impact of a warming climate on coral reefs - coral bleaching. Rising sea temperatures result in the required temperature for corals, and the photosynthetic single celled organisms (zooxanthellae) that have a symbiotic relationship with them, to be exceeded. This can cause mass coral bleaching events due to the zooxanthellae, that give the coral its colour, being expelled or dying. As well as allowing the development of coral bleaching knowledge, this paper also models future changes, unfortunately painting a fairly grim picture. It suggests that mass coral bleaching events will become much more commonplace and that current warming cannot continue without the global loss and degradation of coral reef. Although sea surface temperatures have increased in the past, the speed at which change is currently occurring prevents the marine ecosystem from adapting to change.
DOI: 10.1071/MF99078