Coastal Review Online: Study Finds Alarming Rate of Expansion of ‘Ghost’ Forests
By Lena Beck, Coastal Review Online
Encountering a ghost forest is a decidedly strange experience. Large, stripped tree skeletons remain standing inside long after their death. The other deeply visceral part of the image is the expanse of ghost forests along the North Carolina coast, says Dr. Emily Ury, an ecologist at Duke University who studies ecosystem responses to rapid environmental change. .
“Not just one or two dead trees, but hundreds of dead trees in an area,” Ury said. “You know just by looking at him that it’s not normal.”
Ury is the lead author of a study published this month in the journal Ecological Applications titled “Rapid Deforestation of a Coastal Landscape Driven By Sea Level Rise and Extreme Events”. The purpose of the study was to map the rates of vegetation change in the Alligator River National Wildlife Area on the Outer Banks using remote sensing techniques. Ury and his team analyzed data to measure the evolution of these coastal forests over a period of 35 years. They found that more and more coastal forest land was moving away from the freshwater forest cover, and quickly.
“The speed at which this is happening is fast, even for me, someone who studies climate change and ecological change,” Ury said.
Ury and his team found that 32% of the refuge had changed the land cover classification in the past 35 years, whether due to land loss, forest loss, or brush expansion. This occurs despite the protected status of the study area as a National Wildlife Refuge.
About 19,300 hectares, or nearly 47,000 acres, have been converted to swamp or scrub, while 1,151 hectares have been completely lost in the sea. In addition, about 11% of the forest cover has become what the commonly referred to as a “ghost forest”.
Ghost forests are not a random phenomenon. Most scientists accept the hypothesis that they are caused by increased exposure to salinity. Too much salt can cause widespread tree death, ultimately completely altering the ecosystem. This results in loss of habitat for wildlife and is capable of wiping out entire coastal forests.
Rising sea levels are one of the causes of saltwater infiltration into coastal forests. Data compiled by the Virginia Institute of Marine Science shows that sea levels have been rising every year along the North Carolina coast for decades. While sea level follows a linear curve, Ury’s study shows that ghost forests do not quite follow the same pattern. Instead, ghost forests appear to largely expand after extreme weather events. For example, the refuge saw 4,500 – more or less 990 – hectares of ghost forest form between 2011 and 2012. Ury attributes this highlight of the conversion to the end of a five-year drought and the impact of Hurricane Irene which hit the coast at the end of August 2011.
But in any case, Ury said, the rising tide and extreme weather events are both linked to climate change. In addition, ghost forests are also an indicator of other environmental consequences.
Coastal forests are known to sequester carbon at high rates both in their soil and in their flora, especially trees. When these areas start to convert, some of this carbon is released into the atmosphere.
North Carolina State University’s Dr. Lindsey Smart published a study in 2020 on mapping ghost forests on the Carolina coast. His study looked specifically at the loss of above-ground carbon during habitat conversion. According to Smart, Ury’s study confirms what she and her team of interdisciplinary scientists have also found.
“The Duke study identified the potential role of severe storms and droughts in the proliferation of ghost forests, giving us a better understanding of why these ghost forests can appear in a much shorter time than expected or expected,” said Smart.
Ury’s study was the first mapping effort to use comprehensive remote sensing data, like NASA’s Landsat satellite imagery at 430 miles high. Smart’s work also used this technology in part. According to Smart, the technological capabilities to perform these measurements have grown exponentially over the past decade, as has access to this technology.
“With the increasing availability of remote sensing technologies and access to big data, like this voluntary geographic information and drone imagery, we are truly able to more fully reconstruct the stories of the landscape in time and space. “said Smart.
This evolving technology will allow for further research to better understand why ghost forests appear and what they mean to coastal communities. Additionally, Smart said research is needed to determine how coastal residents perceive ghost forests and what steps they are willing to take to adapt to them. The coast is a mix of public and private land, and any further conversation about ghost forests should take into account the communities affected by them.
“Different landowners have different values for their landscapes,” Smart said. “And it shows how essential it is to involve landowners in the conversation.”
This information would provide a more complete picture of the problem and its consequences, and help scientists like Ury and Smart to more fully reconstruct the stories of these coastal forests.