Just hangin' out

G'day,

I feel that it would be helpful (and perhaps I should have posted this earlier on) to provide a global distribution map of coral reefs so that you can see where they are. Introducing ArcGIS' very own...

The purple denotes the global distribution of coral reefs (2003) whilst the pink denotes the global distribution of cold coral reefs (2005). 

I have been scanning the net trying to find a useful map depicting the coral distribution of the past but I have come up with nothing (or nothing that is good). Therefore, I will use some brief examples of selected areas that have undergone change. 

The Coral Reefs of Eilat by Yossi Loya (2000)

Eilat is a coastal town located in the Gulf of Eliat, nestled between Egypt and Saudi Arabia. This paper by Yossi Loya provides a brief review of the past 35 years of study related to coral species diversity and structure at Eilat. The changes observed have been due to many reasons including natural disturbances (extreme midday low tides), man made perturbations (oil spills) and man's destructive activities (eutrophication). For example, monitoring of the coral community structure at the 'Japanese Gardens' site has revealed that the percentage living cover of stony corals decreased by 75% over the past 15 years and the number of coral colonies by 73%. This has been a direct result of eutrophication only. With the addition of all other known impacts, both natural and anthropogenic, the situation in this location is deeply concerning, as over recent years coral mortality has increased markedly and diversity has drastically decreased. 

Coral Reefs of Indonesia: Past, Present and Future by Anugerah Nontji (1999)

The location and nature of Indonesia makes it a prime spot for coral reefs to grow. There has been a long history of coral reef studies in this region, initially by Rumphius (1705) and then later on by Dutch scientists in the early 1900s with a second wave in the 1960s. This continued research over the centuries shows the importance of coral reefs to this nation. According to Tomascik et al. (1997) the coral reef area of Indonesia is approximately 85,700 km² (14% of the world's total) and the reef biodiversity is the greatest in the world (Rosen, 1971). The Indonesian reefs are susceptible to a number of natural and anthropogenic impacts. This is reflected by the decay in the current conditions of the reefs. Data taken from a paper by Moosa and Suharsono (1997) highlights the significant changes that have occurred over time. The 324 sites indicate that more than 70% of the reefs are either fair or badly damaged whilst only 6.48% are regarded as being in excellent condition. This means that coral coverage is worrying as categories bad to fair denote cover of 0-50% whilst excellent equates to 75-100%. 

So what!?

So, the big picture is worrying. Despite each example being thousands of miles apart, the issues they have faced and continue to face are extremely similar. Furthermore, as a result of these issues, the impact on reef abundance and diversity follow a similar trend. Therefore, it can be assumed (but not with 100% certainty) that the majority of other coral reefs have been impacted in the same way. Thus, if one had the opportunity to work in reverse and create a map of coral distribution for the past based on the information in the papers, then the distribution would most probably be greater. 

Until next time,

Seb