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    When the grass is greener than trees

    Are grasslands more resilient as carbon sinks than forests today? Findings from a new study by the University of California, Davis seem to indicate so with model simulations showing that grasslands can store more carbon than forests.

    Forests have long been considered a critical carbon sink that consumes about a quarter of the carbon dioxide produced by humans worldwide.

    However, massive wildfires are turning California's forests from carbon sinks to carbon sources. The latest findings indicate that the more resilient grasslands and rangelands should be part of the state's cap-and-trade portfolio, which is designed to reduce California's greenhouse gas emissions to 40 percent below 1990 levels by 2030.

    These findings could also serve as guidance for similar carbon offset efforts around the globe, particularly in semi-arid environments, which cover about 40 percent of the planet.

    According to lead author Pawlok Dass, a postdoctoral scholar in professor Benjamin Houlton's lab at UC Davis, grasslands store more carbon than forests because they are impacted less by droughts and wildfires. Good land management, he adds, will also help boost soil health and increase carbon stocks in rangelands.

    This resilience comes from grasslands sequestering most of their carbon underground unlike forests, which store it mostly in woody biomass and leaves.

    During wildfires when trees go up in flames, the sequestered carbon is released back into the atmosphere.

    A similar fire can consume entire grasslands but since the carbon is sequestered underground, it tends to stay in the roots and soil.

    Co-author Houlton, director of the John Muir Institute of the Environment at UC Davis states that trees in a stable climate store more carbon than grasslands but these carbon sinks could be lost in a vulnerable environment. It’s therefore important to use this information to reduce the risk to the carbon investment and conservation strategies in the 21st century.

    Ranchers in California have begun employing innovative land management techniques to improve carbon storage, which can further boost the ability of grasslands to store carbon in the future.

    While the study does not suggest that grasslands should replace forests, it underlines the importance of conserving grasslands and encouraging rangeland practices that promote reliable rates of carbon sequestration, which could help the state meet its emission-reduction goals.

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