The creation of ghost forests is driven by physical, ecological, and disturbance factors but remains a rare phenomenon

Abstract

Marine transgression and the landward migration of coastlines in response to sea-level rise will determine the future of coastal ecosystems and species worldwide, yet no complete model of these processes exist. Ghost forests, areas where coastal forest has been killed by saltwater inundation, are an attention-grabbing early indicator of marine transgression. Research on marine transgression to date has largely been limited to place-based studies that, due to logistical constraints and foci of expertise, investigate subsets of the potential drivers of marine transgression. Here I take advantage of new open source datasets to provide the first systematic analysis of marine transgression across large scales, focusing on the creation of ghost forests across a region of ecological and scientific importance, the northeast U.S. My analysis provides the first synthesis of the physical, ecological, and disturbance factors that influence marine transgression. It also provides crucial regional context for more intensive studies that have a limited geographic scope. I found that ghost forests are a rare phenomenon in the landscape context: 95% of recent forest loss is concentrated in less than 3.86% of marshes, and between 2000 and 2018, only 0.88% of the entire forested area of the transgression zone experienced loss. As a result of this rarity, regional variation in marine transgression is largely driven by opportunities for rare events, which are more numerous when suitable conditions, such as shallow slopes, cover extensive areas. Quantifying recent trends in the rate of forest loss found little evidence of acceleration, with evidence instead suggesting that fewer ghost forests are being created. I also found that physical, ecological, and disturbance factors, including hurricane impacts, were all important for understanding recent trends in forest loss, suggesting that an interdisciplinary approach is warranted for future analyses and modeling of marine transgression. Such interdisciplinary research is urgently needed, as the current rate of marine transgression points to the likelihood of near-term losses of coastal wetlands, with dire implications for the species that depend on them.