In the last three years, the Northeast experienced devastating floods from rainfall and urban wildfires from drought. These extremes are emblematic of changes in environmental variability worldwide – increasing fluctuations in temperature and precipitation. Environmental variability poses a particular challenge to animals that change environments during their lifetime, like insects and amphibians that live in water as juveniles and on land as adults. The best traits for surviving environmental fluctuations are different in water and on land, but individuals need to balance these conflicting pressures. One strategy is to spend less time in the environment where the risks are greatest. For example, many species mature early to escape dangerous juvenile environments, but maturing early can have consequences later in life. This research asks how maturing early in response to environmental variability affects traits of juveniles and adults, survival of each life stage, and population dynamics. Researchers will study a salamander that lives in headwater streams in New Hampshire, metamorphoses from an aquatic larva to an adult that lives on land, and shifts the timing of metamorphosis based on fluctuations in streamflow. This research will also identify headwater areas that provide the greatest services to humans. Headwater streams are the origins of freshwater resources humans rely on for survival, but with millions of kilometers of headwaters in the USA, it is difficult to identif