• Earth's coldest forests are shifting nor

    From ScienceDaily@1:317/3 to All on Thu Feb 24 21:30:42 2022
    Earth's coldest forests are shifting northward with climate change


    Date:
    February 24, 2022
    Source:
    Northern Arizona University
    Summary:
    New research shows rising temperatures are causing Earth's coldest
    forests to shift northward, raising concerns about biodiversity,
    an increased risk of wildfires and mounting impacts of climate
    change on northern communities.



    FULL STORY ==========================================================================
    New research from Northern Arizona University shows rising temperatures
    are causing Earth's coldest forests to shift northward, raising concerns
    about biodiversity, an increased risk of wildfires and mounting impacts
    of climate change on northern communities.


    ========================================================================== Logan Berner, assistant research professor in the School of Informatics, Computing, and Cyber Systems (SICCS) and Scott Goetz, Regents' professor
    and director of the GEODE Lab, authored the article, "Satellite
    observations document trends consistent with a boreal forest biome
    shift," which was published Thursday in Global Change Biology. The boreal forest is a belt of cold-tolerant conifer trees that stretches nearly
    9,000 miles across northern North American and Eurasia; it accounts
    for almost a quarter of the Earth's forest area and is the coldest --
    though mostly rapidly warming -- forest biome.

    For this study, the researchers used 40 years of moderately fine (30m) resolution satellite observations and various geospatial climate-related datasets of the boreal forest and assessed where and why vegetation
    greened and browned during recent decades. "Greening" indicates higher
    rates of vegetation growth, which can happen when climate warming promotes growth of trees and shrubs, as was observed near the arctic and alpine
    tree lines. "Browning" indicates lower rates of vegetation growth and potentially vegetation death, such as when hotter and drier conditions
    suppress tree growth and kill trees.

    "There is emerging evidence that climate change is causing boreal trees
    and shrubs to expand into arctic and alpine tundra, while at the same
    time causing trees to become more stressed and die along the warm southern margins of the boreal forest," Berner said. "These dynamics could lead to
    a gradual northward shift in the geographic extent of the boreal forest
    biome, but the extent to which such changes are already underway has
    remained unclear." What they found wasn't exactly a surprise. Vegetation became greener across much of the cold northern margins of the boreal
    forest; warmer conditions led to increased vegetation growth and enabled
    trees and shrubs to expand into arctic and alpine tundra. Conversely, vegetation became browner along parts of the warm southern margins
    of this biome as a result of hotter, drier conditions increasing tree
    stress and death. Intriguingly, Berner said, vegetation was more likely
    to become greener in areas with high soil nitrogen, indicating that
    soil nutrient availability is an important constraint on the response
    of boreal vegetation to climate change.

    "The boreal forest ecosystem is changing in many ways over recent decades,
    and those changes are often linked with increasing fire disturbance,"
    Goetz said.

    "Here we intentionally focused on areas that were not recently disturbed
    by fire so we could tease out the effect of climate change. Our
    hypotheses about what would happen were verified by this analysis --
    forests are getting more productive in the cooler northern and higher
    elevation areas, and they're getting less productive as a result of hot
    air masses and drying in the warmer and more southerly areas. We fully
    expect that will continue and probably intensify in the years to come."
    What a changing biome means for the forest Changes in vegetation could
    affect both plant and animal biodiversity, especially species like caribou
    and moose, which have specific foraging preferences (e.g. deciduous
    shrubs and trees). These wildlife species are critical sources of food
    for subsistence communities in the boreal- tundra ecotone. Changes in vegetation along both the northern and southern margins of the boreal
    forest will impact wildfire regimes, likely increasing the risk of
    more and severe fires. Changes in vegetation also impact the stability
    of carbon-rich permafrost soils and absorption of solar energy by the
    land surface in ways that could accelerate climate warming. Moreover, increasing tree mortality could have widespread implications for forest products while also leading to further degradation of semi-continuous
    and sporadic permafrost.

    These future effects are not limited to the geographical area around
    the forest.

    "Fundamentally, greenhouse gas emissions from human activities are causing Earth's climate to warm, which in turn is leading the boreal forest to
    shift northward, as well as impacting other ecosystems across the planet" Berner said. "To minimize adverse impacts of climate change, efforts
    are needed to dramatically reduce greenhouse gas emissions, especially
    related to fossil fuel consumption and deforestation. Furthermore,
    northern communities need to plan for potential changes in vegetation
    that could impact resource availability (e.g. wildlife, timber) and
    wildfire risk." This study is part of a larger initiative funded by
    NASA's Arctic-Boreal Vulnerability Experiment (ABoVE) that will include
    further efforts to understand the extent, nature, cause and consequence
    of an emerging boreal biome shift. Goetz is the science lead for ABoVE.

    ========================================================================== Story Source: Materials provided by Northern_Arizona_University. Note:
    Content may be edited for style and length.


    ========================================================================== Journal Reference:
    1. Logan T. Berner, Scott J. Goetz. Satellite observations document
    trends
    consistent with a boreal forest biome shift. Global Change Biology,
    2022; DOI: 10.1111/gcb.16121 ==========================================================================

    Link to news story: https://www.sciencedaily.com/releases/2022/02/220224091126.htm

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