• Scientists estimate invasive insects wil

    From ScienceDaily@1:317/3 to All on Monday, March 14, 2022 22:30:38
    Scientists estimate invasive insects will kill 1.4 million US street
    trees by 2050

    Date:
    March 14, 2022
    Source:
    British Ecological Society
    Summary:
    A new study estimates that over the next 30 years, 1.4 million
    street trees will be killed by invasive insects, costing over 900
    million dollars to replace.



    FULL STORY ==========================================================================
    A new study estimates that over the next 30 years, 1.4 million street
    trees will be killed by invasive insects, costing over 900 million dollars
    to replace. The findings are published in the British Ecological Society's Journal of Applied Ecology.


    ========================================================================== Researchers from McGill University, the USDA Forest Service Southern
    Research Station and North Carolina State University have made the
    first nationwide spatial forecast of street tree mortality from invasive insects, using data from roughly 30,000 urban areas across the United
    States.

    90% of the 1.4 million trees deaths forecasted in the study are predicted
    to be caused by the emerald ash borer (Agrilus planipennis), which is
    expected to kill virtually all ash trees in more than 6000 urban areas.

    The researchers predict that the impact of invasive insects will not
    be evenly spread across the country, with less than a quarter of US
    communities set to experience 95% of all street tree mortality resulting
    from invasive insects.

    Hotspots identified in the study include New York, Chicago and
    Milwaukee. These are areas with very high numbers of ash trees and are
    in the recent or near- future path of the emerald ash borer. Large human populations are also predicted to increase the influx of invasive insects
    to an area.

    The researchers also forecasted the risks of insect species that have
    not yet arrived in the US. Asian wood boring insects, like the citrus longhorned beetle (Anoplophora chinensis), were seen to pose the highest threat, with new establishments of these species potentially costing
    4.9 billion dollars over the next 30 years.



    ==========================================================================
    The researchers say that their findings can also help urban tree managers
    to know which tree species, in which areas, will be at the greatest
    risk from invasive insects. This information can be used to prioritise management efforts such as quarantining wood products.

    Dr Emma Hudgins at McGill University and lead author of the research
    said: "These results can hopefully provide a cautionary tale against
    planting a single species of tree throughout entire cities, as has been
    done with ash trees in North America. Increasing urban tree diversity
    provides resilience against pest infestations. While we know this more intuitively for monocultures of crops, many cities continue to plant
    what are essentially monoculture urban forests." Professor Jane Memmott
    at the University of Bristol, who was not involved in the study said:
    "Urban trees do a variety of wonderful things -- they keep cities cool,
    they take the sting out of heavy downpours, they are good for biodiversity
    and they even make people happier.

    "This paper shows that unless we plant a variety of tree species in our
    cities, urban trees are seriously at risk from invasive pests. The take
    home message to urban planners, is to plant multiple species in cities
    rather than focus on just a few familiar species; It'll keep trees
    wonderful, and it will keep them in our cities." While the findings
    of this study specifically relate to the US, the same invasive insect
    species can impact urban trees in neighbouring countries.



    ==========================================================================
    Dr Hudgins said: "We can see a similar situation in Canada, since emerald
    ash borer arrived here by spreading across the border with the United
    States, and cities like Montre'al are in the process of losing all of
    their ash trees.

    Colder cities like Winnipeg appear to be seeing delayed impacts of
    emerald ash borer due to its need to complete a longer life cycle at low temperatures." Trees form an important part of our urban environments
    and provide a host of benefits including improving air quality, cooling streets, carbon capture, habitat provision for wildlife and improving
    citizens' mental and physical health.

    However, human activity such as trade and travel expose urban trees
    to higher numbers of invasive species. Urban environments also create conditions that allow invasive species to easily spread.

    Dr Koch explains: "Many urban areas are dominated by a single tree species
    or genus, which means that a newly arrived insect for which those trees
    are a host can spread easily. On top of this, there are usually fewer
    natural predators and warmer temperatures compared to nearby natural
    forests, which can benefit invasive insect development." To forecast the impacts of invasive insects on US street trees over the next 30 years,
    the researchers combined a series of four models. These included models
    of street tree populations in 30,000 communities, the predicted spread
    of 57 invasive insect species, how deadly these insects are to different
    tree species, and the cost of removing and replacing dead trees.

    Due to the availability of accurate data, the study focussed specifically
    on street trees, which represent a small fraction of all urban trees. The
    study also only forecasted the economic costs to municipalities
    dealing with street trees being killed and not wider the ecological
    impacts. Dr Koch said: "The ecological impacts of losing urban trees or
    an invasive species moving from urban to natural forests would both be considerable. However, these impacts were beyond the scope of our study."

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


    ========================================================================== Related Multimedia:
    * Emerald_ash_borer ========================================================================== Journal Reference:
    1. Emma J. Hudgins, Frank H. Koch, Mark J. Ambrose, Brian
    Leung. Hotspots of
    pest‐induced US urban tree death, 2020-2050. Journal of
    Applied Ecology, 2022; DOI: 10.1111/1365-2664.14141 ==========================================================================

    Link to news story: https://www.sciencedaily.com/releases/2022/03/220314095722.htm

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