• Nature-based solutions in mountains can

    From ScienceDaily@1:317/3 to All on Wed Mar 9 21:30:50 2022
    Nature-based solutions in mountains can reduce climate change impact on drought

    Date:
    March 9, 2022
    Source:
    University of Cape Town
    Summary:
    New research has shown how catchment restoration -- through the
    management of alien tree infestation in the mountains of the
    southwestern Cape -- could have lessened the impact of climate
    change on low river flows during the Cape Town 'Day Zero' drought.



    FULL STORY ==========================================================================
    New research, led by Dr Petra Holden from the African Climate and
    Development Initiative (ACDI) at the University of Cape Town (UCT),
    has shown how catchment restoration -- through the management of alien
    tree infestation in the mountains of the southwestern Cape -- could have lessened the impact of climate change on low river flows during the Cape
    Town "Day Zero" drought.


    ========================================================================== Climate change is impacting extreme weather events such as droughts
    and floods.

    Nature-based solutions, such as catchment restoration, involve working
    with ecosystems and landscapes to address societal challenges. These
    challenges include the impacts of climate change on water resources. Up
    to now, studies have not separated the role of nature-based solutions
    in reducing the human- driven climate change impacts of extreme events
    on water availability from that of natural climate variability.

    Wanting to inform water resource adaptation planning, this new study
    by an all- southern African based research team published in a Nature
    portfolio journal, Earth Communications & Environment,set out to do this
    using the Cape Town Day Zero drought as an example. Their focus was on a typical type of catchment restoration in South Africa -- invasive alien
    tree management.

    "Invasive alien trees have higher transpiration rates, compared to the
    native vegetation of the Cape mountains, and thus reduce streamflow,"
    Holden explained.

    The research team linked climate models and a hydrological model to
    simulate streamflow during the "Day Zero" drought. They then tested how
    severe the hydrological drought would have been if there had been no human-driven climate change. Their focus was specifically on the impacts
    of climate change and alien tree management on streamflow from mountainous catchments that supply dams critical for water supply to Cape Town.

    Holden shared: "Existing studies do not isolate the effect of nature-based solutions on the anthropogenically derived (i.e., human-derived) portion
    of climate change, especially for drought events that have already
    occurred. Few studies attribute biophysical impacts to human-caused
    climate change impact on drought events while simultaneously investigating
    the role of nature-based solutions in modulating this impact." This new analysis shows that climate change reduced streamflow during the drought
    by 12-29% relative to a world without human-influence on the climate.

    Furthermore, it shows that clearing alien trees that were present in the catchments before the drought hit could have reduced the anthropogenic
    climate change impact on streamflow, but the effect was dependent on
    the extent of invasion.

    Clearing moderate levels of invasion (such as 40% coverages seen in
    some catchments) would have resulted in a 3-16% amelioration of the human-derived climate change impact on streamflow. Preventing the spread
    of alien trees from current levels to full catchment invasion avoided additional reductions of 10- 27% in streamflow due to anthropogenic
    climate change.

    The researchers also found that the impact of climate change was amplified
    due to catchment hydrological processes. For example, the reductions
    in streamflow (12-29%) were larger than the reductions in rainfall
    caused by anthropogenic climate change (7-15%). Despite the role that evapotranspiration can play in drought events, the researchers found some
    but not a large impact of climate change on reference evapotranspiration.

    This is an important study for highlighting the power of quantitative assessments for informing climate change adaptation planning. The
    researchers were able to show that catchment restoration reduced the
    impact of anthropogenic climate change but was not able to remove the
    full signal of human-driven climate change completely, even under current levels of warmings.

    Given this, the researchers highlight that it is critical to combine
    nature- based solutions with other adaptation strategies and options
    for water resource planning to combat accelerated climate change impacts.

    "Teasing out the contribution of adaptation strategies -- be they
    nature-based or not -- for buffering society from human-driven versus
    natural variability in climate can be challenging. However, it is
    important to inform adaptation planning so that climate risk management strategies can be combined in ways that consider thresholds and limits
    to change," concluded Holden.


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


    ========================================================================== Journal Reference:
    1. Petra B. Holden, Alanna J. Rebelo, Piotr Wolski, Romaric
    C. Odoulami,
    Kamoru A. Lawal, Joyce Kimutai, Tiro Nkemelang, Mark
    G. New. Nature-based solutions in mountain catchments
    reduce impact of anthropogenic climate change on drought
    streamflow. Communications Earth & Environment, 2022; 3 (1) DOI:
    10.1038/s43247-022-00379-9 ==========================================================================

    Link to news story: https://www.sciencedaily.com/releases/2022/03/220309103748.htm

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