Will insects be responsible for the death of trees in the future? Well, a new study estimates that 1.4 million street trees will be killed by invasive insects over the next 30 years.
The Researchers from McGill University, the USDA Forest Service Southern Research Station and North Carolina State University came up with the estimates. The British Ecological Society’s Journal of Applied Ecology published the findings.
WILL ASH BORER BE DESTRUCTIVE?
The researchers used data from roughly 30,000 urban areas across the United States. The study found that 90 per cent of the 1.4 million trees deaths would be caused by emerald ash borer. It is expected to kill virtually all ash trees in more than 6000 urban areas.
HOW EVEN WILL BE THE EFFCET?
The researchers predict that the impact of invasive insects will not be evenly spread across the country. Less than a quarter of US communities are set to experience 95 per cent of all street tree mortality. New York, Chicago and Milwaukee are the hotspots identified . These are areas with very high numbers of ash trees. These are in the recent or near-future paths of the emerald ash borer. Large human populations are also predicted to increase the influx of invasive insects to an area.
WILL OUTSIDE INSECTS CAUSE DESTRUCTION?
The study also talks about the risks of insects that have not yet arrived in the US. Asian wood boring insects such as citrus longhorned beetle (Anoplophora chinensis), were seen to pose the highest threat. The researchers say that the 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.
Lead Author Dr Emma Hudgins (McGill University) said pointed out that the findings provided 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,” Emma Hudgins said.
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 Montréal 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.