A Moment of Silence for Our Native Forests?
By Chris Williams on December 16, 2016.
This blog is about a pest problem that an exterminator normally doesn’t face but that we all should be concerned about. Unprecedented damage is being done to our native forest trees by pest invasions that are further encouraged by climate changes.
Being hit the hardest are forests in California, Colorado, North Carolina, Florida, parts of the Midwest and in the Northeast. Forests here in New Hampshire, Massachusetts, and Maine are being devastated in large part due to record warm temperatures that put trees under stress and leave them less able to fight off pests and disease.
Why Invasive Pests Are Calling the Shots
Most of our major pest issues in the U.S. can be attributed to “invasive species” (see What is an Invasive Species?). These are pests that are not native and are relatively new to this country, often entering on ships or planes in packing materials or on garden plants. In their native countries, these insects are kept in balance by native predators and diseases that have evolved along with them. Once here, these new species have no native predators or diseases, they are free to run amok. They outcompete similar native insect species for the same territory and resources.
Weather is a Factor
The same increasingly warm temperatures that put our native trees at a new disadvantage are an advantage for many pests, especially new invasive pests that are used to more tropical environs. The recently introduced emerald ash borer is quickly destroying ash forests. It was first found in the U.S. in 2002, is now present in 30 states, and has killed hundreds of millions of trees. The invasive hemlock woolly adelgids suck sap from conifer needles and are expected to put 63% of the country’s forests at risk through 2027.
Even native pests, though, are warming to higher temperatures and resulting dry conditions. Exploding populations of native bark beetles are wiping out entire forests in drought-stricken Colorado and California. Drought weakens the trees and higher temperatures speed up development time for the insects.
It’s not just huge forest stands that are affected, the devastation can hit close to home. In Worcester, Massachusetts, 31,000 trees had to be removed in 2008 as a result of an Asian longhorned beetle infestation. And, the emerald ash borer is just as likely to infest that ash tree in your backyard. When it hits home, you pay attention.
Can We Save Our Forests?
The death of a forest has long-ranging effects that go beyond just economic losses to the timber industry. The impact on birds, animals and other species that depend on the forest can’t be calculated. Fire hazards increase across millions of acres of dead trees.
Scientists, of course, are rapidly working on cures. Pesticides are not usually a practical choice because of the vast forest areas involved. Some of the cures require the release of yet another foreign species to control those already present. Parasitic wasp species are being released in 24 states in an attempt to stop the emerald ash borer (see There Might Yet Be Hope for Our Ash Trees). Genetic modifications of the pests to prevent development or successful reproduction are also being used, and the trees themselves are being genetically modified to resist attack by pests and diseases.
It probably comes down to whether native trees will be able to adapt to weather changes and drought quickly enough to fight back against those insects that want to do them in. Eventually, even invasive species are attacked and controlled by other organisms. Fortunately, Mother Nature abhors a vacuum. Many trees will die, some species may largely disappear, but some trees will become resistant to the drought and the pests…and those trees will reproduce and hopefully repopulate devastated areas.