• Human activity on rivers outpaces, compo

    From ScienceDaily@1337:3/111 to All on Fri Jun 19 21:30:30 2020
    Human activity on rivers outpaces, compounds effects of climate change


    Date:
    June 19, 2020
    Source:
    University of Illinois at Urbana-Champaign, News Bureau
    Summary:
    The livelihoods of millions of people living along the world's
    biggest river systems are under threat by a range of stressors
    caused by the daily economic, societal and political activity of
    humans -- in addition to the long-term effects of climate change,
    researchers report.



    FULL STORY ==========================================================================
    The livelihoods of millions of people living along the world's biggest
    river systems are under threat by a range of stressors caused by the
    daily economic, societal and political activity of humans -- in addition
    to the long-term effects of climate change, researchers report.


    ==========================================================================
    A new paper by University of Illinois at Urbana-Champaign geology and
    geography professor Jim Best and University of Southampton professor
    Stephen Darby takes a big-picture approach to review the health and
    resiliency of the world's large river systems, their deltas and their vulnerability to extreme events.

    The article is published in the journal One Earth.

    Rivers respond to changes in the environment through self-adjusting
    processes of erosion and sedimentation, the researchers said. When not
    stressed by extreme events like flooding or drought, these responses
    typically allow rivers to absorb change. However, data from many new
    studies now suggest that the world's great waterways are becoming more vulnerable as the effects of human activity and climate change combine
    and compound.

    "Climate change is of huge importance in terms of changing flood or
    drought frequency and intensity," Best said. "However, there is a range
    of other stressors affecting big rivers such as damming, sediment mining, pollution, water diversions, groundwater extraction and the introduction
    of nonnative species -- all of which affect rivers on a timescale that
    has much more immediate consequences." For example, the team reviewed
    past research on the drivers of flooding in the Mekong River Delta in
    Southeast Asia, which supports about 18 million people and a vast rice agricultural area. These studies suggest that delta subsidence -- or
    sinking -- because of groundwater extraction beneath the delta is now
    more of a problem, as the region receives far less sediment because of
    sediment trapping behind upstream dams and large-scale mining of sand
    from the bed of the delta's channels.

    "The scale of the effects of sediment starvation and subsidence in
    driving increased flood risk is currently far greater than sea-level rise generated by global climate change," Best said. "But when all of these pressures are combined, there is now a real risk that we could cross
    a major tipping point in the next 10-20 years." Politics also play
    a significant role in the health and resiliency of the world's major
    river systems, the paper reports. For example, the current COVID- 19
    pandemic is influencing regulatory enforcement of pollution monitoring
    in the United States, enabling polluters to avoid penalties if they
    argue violations are a result of the pandemic.

    "We have seen evidence of the effect of these types of political and
    societal shocks on river systems in the past, too," Best said. "The
    stresses from the Gulf War led to increased river pollution in the Tigris-Euphrates River Basin, a situation that was also compounded by
    upstream damming in Turkey." The researchers stress an urgent need
    for governance at the local level across to the international level to
    confront these issues effectively.

    "There are some things we as scientists can do on the monitoring end of
    this issue, but it will demand collaboration and trust between nations
    for it to make a difference," Best said. "We can't take our eye off the
    ball -- we've just got to devote more attention to these more frequent, shorter-timescale stressors. It's far from being just about climate
    change."

    ========================================================================== Story Source: Materials provided by University_of_Illinois_at_Urbana-Champaign,_News_Bureau.

    Original written by Lois Yoksoulian. Note: Content may be edited for
    style and length.


    ========================================================================== Journal Reference:
    1. Jim Best, Stephen E. Darby. The Pace of Human-Induced Change
    in Large
    Rivers: Stresses, Resilience, and Vulnerability to
    Extreme Events. One Earth, 2020; 2 (6): 510 DOI:
    10.1016/j.oneear.2020.05.021 ==========================================================================

    Link to news story: https://www.sciencedaily.com/releases/2020/06/200619115723.htm

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