My work as a quantitative ecologist examines how ecosystems respond to external factors such as adding nitrogen. In a recently published study, I worked with colleagues to quantify nitrogen runoff from land into rivers and streams. We found that infrequent but heavy rainfall events account for one-third of annual total runoff and nitrogen leaching from soils across the Mississippi Basin. This tells us that managing nitrogen is likely to be more challenging if climate change continues to make heavy rains more frequent.