In a recent study by North Carolina State University and the U.S. Geological Survey (USGS), researchers explored how satellite imagery could help conservationists identify forested areas at risk of becoming marshes or open water due to sea-level rise, a transformation known as "regime change." Marcelo Ardon, an associate professor at NC State and study co-author, emphasized that this modeling tool could support targeted conservation strategies.

"We know that these coastal ecosystems are changing, and it's hard to predict where and when the change is going to happen. What we found is that through remote sensing, you can get a trajectory of where an area is going," Ardon said.

"That way you can identify which areas might be better to put funding into; if an area might not need help, or if it is just too far into the regime change to pull it back. That in turn can help allocate those limited conservation dollars where they will make the most difference."

The research initially aimed to assess whether satellite data could detect early-warning signals of regime changes in coastal wetlands, similar to signals found in other ecosystems. However, these attempts yielded inconsistent results, as data often produced false positives and negatives. Instead, the researchers used the satellite data to measure vegetation health using the Normalized Difference Vegetation Index (NDVI).

The NDVI uses various wavelengths collected by satellite sensors to analyze the amount of red and near-infrared light plants absorb and reflect, respectively. Higher NDVI values generally indicate a healthy, green forest, while lower values correspond to marsh or open water, allowing researchers to monitor shifts in vegetation health over time.

Melinda Martinez, a research ecologist with the USGS and lead author of the study, noted significant variations in the pace of regime changes across sites, even in areas that were geographically close.

"In some areas where regime change was happening quickly, the transitions from forest to marsh or even open water happened within the span of five to six years," Martinez said. "But then in other areas, sometimes places within the same site, it would happen over much longer periods of time. We knew there would be variation, but we didn't expect that level of difference between areas in such proximity."

Research Report:Detecting trajectories of regime shifts and loss of resilience in coastal wetlands using remote sensing

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