Ghost Reefs

A research article published last month in the journal Science Advances details coral losses that are greater than previously imagined. These findings shed new light on the impact of human development on our oceans, a particularly hot topic today as documentaries like Netflix’s Chasing Coral reveal an all too grim story. Led by author Loren McClenachan at Colby College in Maine, the study reports an overall loss exceeding 50% of the area historically covered by coral reef in the Florida Keys, with losses of over 80% in some inshore areas.

Treasure Maps

Chart comparion of coral loss

Example of nearshore coral loss near Key West, Florida. Science Advances 06 Sep 2017: Vol. 3, no. 9, e1603155 DOI: 10.1126/sciadv.1603155

Most modern assessments of coral reef health are typically based on areas with existing coral reef coverage. This method can provide important information of present-day coral decline, but may overestimate long term losses. In this study, the authors sourced 18th century British nautical charts to assess coral declines over the last 240 years. The authors detail coral losses by overlaying modern satellite imagery with these historic charts to provide a more accurate representation of long-term decline.

Human Impact

In 1906 construction began on a railway linking the islands of the Keys, coinciding with abrupt changes in coral coverage during the early 20th century. This development, coupled with land-conversion and drainage of the Everglades, likely altered the surrounding ecosystem, creating the high inshore coral losses. Samples from the same time period show an increase in salt content and carbon levels, and a decrease in freshwater input; both culprits to coral decay.

Protecting Coral

Reef habitats are important sanctuaries for many marine species throughout the world. South Africa aims to protect 15% of it’s coastline by 2028 by proposing 22 new Marine Protected Areas (MPAs). These areas will help to protect and maintain the biodiversity of underwater resources by regulating and reducing the impact of human activities within them. Our research projects at Cape RADD aim to provide long-term monitoring of the diversity and abundance of life within some of these areas to ensure the health of our oceans into the future.


Ghost reefs: Nautical charts document large spatial scale of coral reef loss over 240 years
By Loren McClenachan, Grace O’Connor, Benjamin P. Neal, John M. Pandolfi, Jeremy B. C. Jackson
Science Advances : e1603155

Categories: News

Dylan Irion

Dylan is a marine scientist and Save Our Seas Foundation project leader, working towards a PhD that aims to unravel the drivers of white shark population dynamics in South Africa. He is a passionate freediver and SCUBA diver, and volunteers as a Sea Rescue crew member.


Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.