Ghost Forests Are Not All Bad

by SC Guest Contributor Barbara Joy Cooley

A snag on Silver Key, decorated with shells.

A ghost forest is an area of dead or dying trees. Ghost forests that are appearing in coastal Florida these days are generally caused by rising sea level — the increasing intrusion of salt water into a habitat that once supported trees that were not so salt- or water-tolerant. The trees die, leaving only their upright, dead skeletons — called snags — and eroded roots behind.

A snag on Silver Key, decorated with shells.

But there is a ghost forest area on Silver Key in Sanibel that was caused more directly by humans. Years ago, the City of Sanibel killed the invasive exotic Casuarina (Australian Pine) trees on Silver Key. Many of the snags have now fallen, but some remain, and a few of them support osprey nests.

The remaining salt marsh on Silver Key appears to be thriving. Much of it is savanna-like. Part of it is wooded with sea grapes and buttonwoods. And then there’s the beach side of Silver Key, which is in a constant state of change.

Where the beach meets the wooded area is a bit of the other kind of ghost forest — the kind caused by intruding salt waters. Some of this is evidence of sea level rise, and some is evidence of the naturally alternating erosion and accretion of sand along the shoreline. And some of that sand accretion is not natural; it results from Captiva beach renourishment projects to the north of Silver Key.

Regardless of how the trees died, they leave behind intriguingly beautiful dead wood in the form of twisted limbs and entwined, curly roots. Big old stumps still rooted in the sand are so wet that velvety, luxuriant, bright green moss clings to them.

When I’m tired of looking at sand and shells, the dead wood fascinates me. When I ponder the dead wood, I think about an article I read a few years ago, by Lyndsey Gilpin. She wrote that ghost forests are a sign of nature’s resilience to sea level rise; nature sacrifices the trees to form new marshland which helps to protect inland areas from storm surges.

Old Casuarina roots, covered in moss.

The study of ghost forests is something that has been happening mostly since the 1980s, according to Gilpin. In places like Silver Key, what was once a forest of taller trees is now mangrove forest — a type of forest that sequesters far more carbon than rainforests do.

But where taller forests are replaced by perennial grasses, there is less carbon sequestration happening. More research is needed to understand the net effect.

Gilpin writes that one of those who are researching ghost forests, Matthew Kirwan at the Virginia Institute of Marine Science, says that if you look at ghost forests and see dead trees, “you’re a pessimist; and if you see marsh, you’re an optimist.”

Maybe we need to be both.

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