‘Warming’ is often the focus of concerns regarding global change, but it is frequently a shift in water balance that will be the driver of major ecosystem changes. The Nature Conservancy is linking four conservation projects in China, Alaska, Bolivia and North Carolina to create a sensitive detector of global climate change. The focus in each location is on possible dramatic changes in water balance that could threaten native ecosystems, such as shifting monsoon patterns in China, permafrost thaws in Alaska, a rise in sea level around North Carolina and lengthened dry seasons in Amazonian Bolivia.