b'Carnegie Science|Summer 2019 7Rainfall and Temperature Changes Impact Water QualityWe wanted to see whether we could find evidence in the historical record of changes in temperature and precipitation affecting the amount of nitrogen that gets into Stanford graduate student Tristan Ballard (left) in Anna Michalaks watersheds (right) Global Ecology lab was lead author on the Environmental Science & Technology paper.C hanges in temperature andAgriculture played a role, too, but itfields. Its also about how human action at precipitation have alreadywas more complicated than a simplea global scale is changing rainfall and impacted the amount ofone-on-one correlation.temperatures, Michalak said. Its a nitrogen introduced into U.S.For example, in the northern Greatcomplex system, but it comes down to waterways, according to newPlains, increased farming and climatebetter managing human impacts across research from a team of threeconditions compounded to put morescales, from your own backyard to the Carnegie ecologists published innitrogen in the waterways. However, inplanet as a whole. Environmental Science & Technology the Great Lakes, despite efforts to reduceThe team says their findings mean .Nitrogen from agriculture and otherthe amount of nitrogen released bythat management strategies will become human activities enters waterways, which,human activity, precipitation increased soeven more challenging over time. Simply in excess, creates a dangerous phenomenonmuch that nitrogen still overloaded thedecreasing the amount of nitrogen called eutrophication. This can lead towater system.released by industry and farming will not toxin-producing algal blooms or low-oxygenWhat we have shown is thatbe enough. The decreased usage will have dead zones. Over the past several summers,deteriorating lake and coastal waterto be enough to offset greater risk due to dead zones and algal blooms in lake andquality is not just about how we developincreased precipitation, too.coastal regions across the United Statesland and how much fertilizer we use on have received extensive news coverage.Carnegies Anna Michalak and her team have spent several years studying the effects of nitrogen runoff and how expectedTotal nitrogen flux trends Contribution of climate effectschanges in precipitation patterns due to climate change could lead to greater risks to water quality. But their efforts so far have focused on making predictions of the future. Now, with Tristan Ballard, they looked backward to analyze long-term trends in nitrogen runoff going back to the 1980s. We wanted to see whether we could1987 to 2012 1987 to 2012find evidence in the historical record of changes in temperature and precipitationImproving Degradingaffecting the amount of nitrogen that getsConditions Conditionsinto watersheds in the contiguous U.S., said-111 -75 -50 -25-5 5 25 5075 118 kg-N km -2lead author Ballard. Our findings couldyr -1 decade -1 improve our modeling of future risks and guide management efforts.They found that climate was a keyLong-term trends in total nitrogen accumulation from 1987 to 2012 are shown across the U.S. The scientists found that heavy spring precipitation and temperature drove the nitrogen runoff trends in most factor in how much nitrogen ended up inareas. They also found that rising temperatures were not sufficient to offset the nitrogen increases from the water system, with warming springtimeprecipitation. That finding suggests that temperature increases with climate change will not likely counteract nitrogen increases in the future. temperatures and accompanying stormsImage courtesy the American Chemical Society, from Environ. Sci. Technol. 2019, https://pubs.acs.org/doi/10.1021/acs.having a direct impact on nitrogen runoff.est.8b06898. For additional use contact support@services.acs.org'