Ghost Reefs

[Image: 18th-century nautical chart by George Gauld, via Geographical].

A theme that has near-universal appeal for me is when old maps reveal the presence of something in the landscape that people have otherwise overlooked or forgotten. It could be a lost road deep in the mountain forests of Vermont, for example, or it could a whole series of missing reefs off the coast of Florida.

Earlier this year, a team of researchers led by Loren McClenachan at Colby College in Maine found what they called “ghost reefs” in old nautical charts drawn by an 18th-century British surveyor named George Gauld. When the team compared Gauld’s maps with modern satellite images of the same landscape, “a stark picture of shrinking coral emerged: Half of the reefs recorded in the 1770s are missing from the satellite data,” the Washington Post reported.

There are limitations to the approach, of course: “It’s impossible to tell whether the [18th-century] surveyors distinguished between living and dead coral, for example, or how long the reefs had persisted,” the Post writes, but the idea of finding ghost geographic forms in old maps is too evocative not to mention here.

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