Degradation affects up to 100 million hectares of forest every year, which is nearly 10 times greater than the area impacted by deforestation. However there is very little guidance on how to detect, measure and monitor forest degradation. The Forest Degradation Guidance and Decision Support Tool fills this gap by providing guidance on how and when to monitor and measure forest degradation, and how to incorporate forest degradation into national REDD+ frameworks. This document summarizes the key methods currently being used, offers guidance on critical decisions and provides a framework for the development of a degradation measurement and monitoring plan. This document is part of USAID LEAF’s technical guidance series on developing national and subnational forest monitoring systems for REDD+.