ReportWire

Tag: Carnegie Institution for Science

  • Climate elevates toxin risk in Northern US lakes.

    Climate elevates toxin risk in Northern US lakes.

    [ad_1]

    Newswise — Washington, DC— As climate change warms the Earth, higher-latitude regions will be at greater risk for toxins produced by algal blooms, according to new research led by Carnegie’s Anna Michalak, Julian Merder, and Gang Zhao. Their findings, published in Nature Water, identify water temperatures of 20 to 25 degrees Celsius (68 to 77 degrees Fahrenheit) as being at the greatest risk for developing dangerous levels of a common algae-produced toxin called microcystin.  

    Harmful algal blooms result when bodies of water get overloaded with nitrogen and phosphorus runoff from agriculture and other human activities. These excess nutrients can allow blue-green algae populations to grow at an out-of-control rate.

    Some blue-green algal species produce a toxin called microcystin, which can pose a serious health hazard to people and the environment, as well as pose economic risks for fishing and tourism. Microcystin affects liver function and can cause death in wild and domestic animals, including humans in rare instances. It is also classified as a potential carcinogen in cases of chronic exposure.

    “In 2014 an algal bloom in Lake Erie led to high levels of microcystin in water intakes, and residents in Ohio and Ontario were instructed not to drink tap water due to risk of exposure,” Merder cautioned.

    Merder, Michalak, and their colleagues—Carnegie’s Gang Zhao, University of Kansas’s Ted Harris, and Dimitrios Stasinopoulos and Robert Rigby of the University of Greenwich—analyzed samples taken from 2,804 U.S. lakes between 2007 and 2017. They assessed how water temperature affects the occurrence and concentration of microcystin as part of an effort to better understand the risks to water quality posed by climate change.

    Michalak’s lab has taken a leading role in understanding the intersection of climate change and water quality impairments for more than a decade. Previous work has shown that lakes worldwide are already experiencing more severe algal blooms and that nutrient pollution is being exacerbated by changes in rainfall patterns.

    “Lakes are sentinels of climate change,” Michalak said. “They hold the vast majority, 87 percent, of the liquid freshwater on the Earth’s surface, and the warming and precipitation shifts associated with climate change pose some of the greatest threats to water quality around the world and to the health of aquatic ecosystems.”

    The surface temperatures of lakes have already been warming at 0.34 degrees Celsius (0.61 degrees Fahrenheit) per decade and Merder and Michalak set out to determine what this, as well as future warming, would mean in terms of risk for elevated toxin concentrations.

    “The abundance of blue-green algae is predicted to increase due to climate change as they outcompete other species,” Merder explained. “But previous field studies came to various conclusions about what this means for microcystin concentrations.”

    To inform land and water management strategies, it was important to quantitatively tie toxin levels to water temperature, which Merder and Michalak were able to accomplish through their extensive analysis of lake water samples, revealing that water temperatures in the 20 to 25 degrees Celsius (68 to 77 degrees Fahrenheit) range were most dangerous in terms of elevated microcystin concentrations. They also found that the impact of temperature is amplified when nutrient concentrations are high.

    By incorporating information from climate models, they were able to demonstrate that areas most susceptible to high toxin concentrations will continue to move northward. In some areas, the relative risk of exceeding water quality guidelines will increase by up to 50 percent in the coming decades. Additionally, they showed that toxin hazards will decrease in a small number of regions further south, as water temperatures begin to exceed those associated with the highest risk.

    “These findings should help demonstrate the serious risk to safe water for drinking, fishing, recreation, and other societal needs in many parts of the United States and the urgency for developing management strategies to prepare,” Michalak concluded. “When we think about water sustainability in the context of global change, we need to focus on the quality of the water as much as we focus on the amount of water.”

    [ad_2]

    Carnegie Institution for Science

    Source link

  • Climate Change Exacerbates Complexity of Nitrogen Runoff Mitigation Approaches

    Climate Change Exacerbates Complexity of Nitrogen Runoff Mitigation Approaches

    [ad_1]

    Newswise — Washington, DC— As climate change progresses, rising temperatures may impact nitrogen runoff from land to lakes and streams more than projected increases in total and extreme precipitation for most of the continental United States, according to new research from a team of Carnegie climate scientists led by Gang Zhao and Anna Michalak published in the Proceedings of the National Academy of Sciences.

    The conditions predicted by these findings are opposite to recent decades, when increasing precipitation has outpaced warming and led to more aquatic nitrogen pollution. Understanding the relative roles of changes in temperature and rainfall is critical for designing water quality management strategies that are robust to climate change while ensuring sustainable food and water supplies.

    Human activity has completely altered how nitrogen moves through the planet’s aquatic, terrestrial, and atmospheric systems. Nitrogen from fertilizer washes into waterways and, in excess, can lead to toxin-producing algal blooms or low-oxygen dead zones called hypoxia. Over the past several summers, large algal blooms in lake and coastal regions across the United States have received extensive news coverage.

    Carnegie’s Anna Michalak and her team have spent the last decade studying how climate change will affect nitrogen runoff and the subsequent risks posed to water quality. One of the biggest questions for those working to understand and prevent serious water quality impairments is the balance between how changes in temperature and changes in precipitation will affect nitrogen pollution’s ability to get into at-risk waterways.

    “The complex soil and aquatic systems through which nitrogen travels, the chemical transformations it undergoes along the way, and the various ways in which changes in temperature and precipitation will affect these processes make nutrient management a big challenge,” Zhao explained.

    For example, average and extreme precipitation affects how much nitrogen runs off the land and into waterways, as well as how long it takes for the nitrogen to reach lakes or coastal zones, where it can eventually create dangerous conditions. Temperature also indirectly impacts how much nitrogen ends up in waterways, because warming temperatures increase evaporation, preventing it from going into streams. Temperature also affects how nitrogen interacts with microbial life in the soil and sediment, potentially trapping it there or altering its course.  

    “Although the impacts of climate change-induced shifts in precipitation patterns have been explored, the effect of temperature increases on the movement of nitrogen into rivers has not been quantified at continental scales until now due to a lack of available data,” Zhao added.

    Zhao, Michalak, and their Carnegie colleagues Julian Merder and Tristan Ballard analyzed several decades of data tracking nitrogen’s movement through river systems across the continental United States and used it to project future trajectories for nitrogen movement under climate change scenarios. They determined that rising temperatures will likely offset, or even decrease, the amount of excess nitrogen flushed into rivers for the majority of the U.S., despite a predicted uptick in precipitation.

    These findings are counter to recent decades, when precipitation was the dominant factor over temperature in determining the amount of nitrogen that built up in U.S. waterways. Zhao, Michalak, and their colleagues say that this work forms a critical baseline for future research on the interplay between the nitrogen cycle and climate change.  

    “Our research illustrates the complex, and sometimes surprising, ways that climate change affects our planet’s dynamic systems,” Michalak concluded. “Untangling the various factors that are altering the climate change impacts on water quality will help farmers, land managers, and policymakers to pursue the best possible strategies for ensuring that we safeguard water quality, while simultaneously ensuring sustainable food production and water supply.”

    [ad_2]

    Carnegie Institution for Science

    Source link

  • Carbon Emissions: How Will a Warmer World Affect Us?

    Carbon Emissions: How Will a Warmer World Affect Us?

    [ad_1]

    Newswise — Washington, DC—As the world heats up due to climate change, how much can we continue to depend on plants and soils to help alleviate some of our self-inflicted damage by removing carbon pollution from the atmosphere?

    New work led by Carnegie’s Wu Sun and Anna Michalak tackles this key question by deploying a bold new approach for inferring the temperature sensitivity of ecosystem respiration—which represents one side of the equation balancing carbon dioxide uptake and carbon dioxide output in terrestrial environments. Their findings are published in Nature Ecology & Evolution.

    “Right now, plants in the terrestrial biosphere perform a ‘free service’ to us, by taking between a quarter and a third of humanity’s carbon emissions out of the atmosphere,” Michalak explained. “As the world warms, will they be able to keep up this rate of carbon dioxide removal? Answering this is critical for understanding the future of our climate and devising sound climate mitigation and adaptation strategies.”

    Photosynthesis, the process by which plants, algae, and some bacteria convert the Sun’s energy into sugars for food, requires the uptake of atmospheric carbon dioxide. This occurs during daylight hours. But through day and night, these same organisms also perform respiration, just like us, “breathing” out carbon dioxide.

    Being able to better quantify the balance of these two processes across all the components of land-based ecosystems—from soil microbes to trees and everything in between—and to understand their sensitivity to warming, will improve scientists’ models for climate change scenarios.

    In recent years, researchers—including Carnegie’s Joe Berry—have developed groundbreaking approaches for measuring the amount of carbon dioxide taken up by plants through photosynthesis, such as using satellites to monitor global photosynthetic activity and measuring the concentration of the atmospheric trace gas carbonyl sulfide.

    But, until now, developing similar tools to track respiration at the scale of entire biomes or continents has not been possible. As a result, respiration is often indirectly estimated as the difference between photosynthesis and the overall uptake of carbon dioxide.

    “We set out to develop a new way to infer how respiration is affected by changes in temperature over various ecosystems in North America,” said Sun. “This is absolutely crucial for refining our climate change projections and for informing mitigation strategies.”

    Michalak, Sun, and their colleagues developed a new way to infer at large scales how much respiration increases when temperatures warm using measurements of atmospheric carbon dioxide concentrations. These measurements were taken by a network of dozens of monitoring stations across North America.

    The team revealed that atmospheric observations suggest lower temperature sensitivities of respiration than represented in most state-of-the-art models. They also found that this sensitivity differs between forests and croplands. Temperature sensitivities of respiration have not been constrained using observational data at this scale until now, as previous work has focused on sensitivities for much smaller plots of land.

    “The beauty of our approach is that measurements of atmospheric carbon dioxide concentrations from a few dozen well-placed stations can inform carbon fluxes at the scale of entire biomes over North America,” Sun explained. “This enables a more comprehensive understanding of respiration at the continental scale, which will help us assess how future warming affects the biosphere’s ability to retain carbon,” Sun emphasized.

    To their surprise, the researchers found that respiration is less sensitive to warming than previously thought, when viewed at the biome or continental scale. But they caution that this temperature sensitivity is just one piece of a complex puzzle.

    “Although our work indicates that North American ecosystems may be more resilient to warming than plot-scale studies had implied, hitting the brakes on climate change ultimately depends on us ceasing to inject more and more carbon into the atmosphere as quickly as possible. We cannot rely on the natural components of the global carbon cycle to do the heavy lifting for us,” Michalak cautioned. “It is up to us to stop the runaway train.”

    Other members of the research team include: Xiangzhong Luo, Yao Zhang, and Trevor Keenan of University of California Berkeley and Lawrence Berkeley National Laboratory; Yuanyuan Fang of the Bay Area Air Quality Management District; Yoichi P. Shiga of the Universities Space Research Association; and Joshua Fisher of Chapman University.

    [ad_2]

    Carnegie Institution for Science

    Source link