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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