A recent study reveals how climate change is altering coastal wetlands in North Carolina, transitioning them from forested areas to marshes or even open water. It also highlights the potential role of satellite imagery in guiding conservation efforts to safeguard these ecosystems.
The rise in sea levels due to climate change presents a significant and often unpredictable threat to coastal forests, necessitating the development of new tools to reduce damage and effectively allocate conservation resources.
A collaborative study between North Carolina State University and the United States Geological Survey (USGS) explores how satellite imagery can assist in recognizing forested regions that are transitioning into marshlands and open water as a result of rising sea levels, a phenomenon termed regime change. Marcelo Ardón, an associate professor at NC State and co-author of the study, explained that this new modeling tool can help conservationists allocate their limited funding towards areas that require the most urgent attention.
“We understand that these coastal ecosystems are evolving, and predicting the timing and location of these changes can be challenging. Our findings indicate that remote sensing can reveal the trajectory of land changes,” Ardón stated. “This allows for better targeting of funding; we can assess whether an area may not require intervention or if it is too far along in the transition to be recoverable. This approach ultimately aids in directing limited conservation resources where they will have the greatest impact.”
Initially, the researchers aimed to discover if satellite imagery could proactively identify regime changes in coastal wetlands by detecting early-warning signals observed in other ecosystems. However, Ardón noted that the results were inconsistent, at times yielding false positives and false negatives.
As a result, the researchers employed the same satellite data tool—a metric called the Normalized Difference Vegetation Index (NDVI)—to evaluate changes in vegetation health. The NDVI utilizes various wavelengths from satellite sensors that monitor the Earth at different intervals, gathering information on how much red light plants absorb versus how much near-infrared light they reflect. With these measurements, researchers can calculate the NDVI, which is an effective indicator of plant health and greenness. Forest areas typically show higher NDVI values compared to marshes or open water, making it possible to track environmental changes.
Melinda Martinez, the lead author and a research ecologist at the USGS, initially worked on the study during her Ph.D. at NC State. She observed significant variations in regime changes among nearby locations.
“In certain areas, regime change was rapid, with shifts from forest to marsh or even open water occurring within five to six years,” Martinez explained. “Conversely, in other nearby locations, transitions unfolded over much longer periods. We anticipated some variation, but we were surprised by the degree of difference between areas in such close proximity.”
