Flooding and rising sea levels are causing saltwater to intrude into coastal lowlands, damaging farmland and forests. This increases soil salinity, kills trees, and creates “ghost forests.” As trees die, their roots shrink and decay, forming channels in the soil that allow more water to flow through, which may speed up further damage. There is limited data supporting this process, so this study tested geophysical methods to monitor water movement between trees and soil in healthy and dying trees on the upper Delmarva Peninsula, USA. Researchers used ground-penetrating radar to image large roots, 3D resistivity surveys to track soil moisture changes during rain, and self-potential electrodes inside tree trunks to monitor water movement, supported by sap flow sensors. These methods help study how saltwater affects tree health and underground water flow in threatened coastal ecosystems.