By David Wood
Palaeontologists tell us that the earth’s biosphere has undergone five catastrophic collapses in the 3.1 billion years of its existence. during the most recent of these, the cretaceous extinction, about 65 million years ago, it is believed that 75% of species on earth disappeared. Many scientist now believe that the earth could be entering its sixth mass extinction known as the Anthropocene, meaning that it is caused by humanity.
It is clear that the disappearance of megafauna from Europe, Asia, Australia and the Americas coincides with the migration of humans into each area, suggesting that we caused their extinction. Many additional species were affected as the expansion of agriculture altered preexisting habitats and as man transported plants and animals around the earth. It appears that the burning of fossil fuels is exacerbating, if not causing, global warming, and acidification of the oceans by the carbon dioxide released by burning will push yet more species to, if not over, the brink of extinction. what does any of this have to do with Eastman?
Eastman may be insignificant on the planetary scale, but that is no excuse for not trying to get our own house in order. We have already set a goal of reducing our energy footprint by 25% by 2020. We have purchased substantial tracks of undeveloped land and are attempting to manage them in ways that will diversify the habitat and provide continuous wildlife corridors. Finally, we are attempting to halt and, where possible, reverse the spread of invasive species throughout the community.
What is the connection between invasive species and mass extinction? An invasive species is defined as “an alien species whose introduction does or is likely to cause economic or environmental harm or harm to human health.”1 In Eastman, the concern is the adverse effect of invasive species on habitat diversity and on the survival of the species that depend upon that diversity.
Two invasive insects, the emerald ash borer and the hemlock wooly adelgid, are of particular concern. The white ash and northern hemlock that are susceptible to these insects are among the most common trees in Eastman, and their loss would dramatically alter our woodlands. Although neither of these Asian natives has been detected in the Upper Valley, both have been reported in New Hampshire. In Eastman, the Woodlands and Wildlife Committee is establishing a monitoring program with the goal of early detection and response to any invasion. In the meantime, we can all help to mitigate the risk of invasion by using only locally produced firewood or, better yet, properly kiln-dried wood.
Invasive plants also diminish habitat diversity and reduce the health and range of native species. In Eastman, purple loosestrife, autumn olive, glossy buckthorn, bush honeysuckle, Japanese knotweed and the common reed are the most widespread and invasive of the alien land plants. These and many other plants considered locally invasive are described in detail in a publication available free on the UNH Extension Service website (extension.unh.edu) entitled “New Hampshire Guide to Upland Invasive Species” by Douglas Cygan, New Hampshire’s Invasive Species Coordinator. Similarly, a number of invasive aquatic plants thrive in ponds near us, especially sandwort and variable and Eurasian milfoil, both of which have been prevented from invading Eastman Lake through the efforts of the Lake Host and Weed Watcher programs.
Purple loosestrife (Lythrum salicaria) is a beautiful perennial flower often seen growing in the wet areas in mid-summer. A native of Europe, Asia and northwest Africa where its growth is controlled by endemic insects and pathogens, it is highly invasive in North America, where it forms monocultures that impede the flow of water and crowd out native species, such as cattail, destroying the habitat of both amphibians and algae. The biological control of purple loosestrife in Eastman, begun in 2006 with the, now, yearly release of Galerucella beetles, has made the plant uncommon here.
Glossy buckthorn (Rhamnus frangula) represents the most threatening invasive in our woodlands. Retaining its leaves late into the fall, glossy buckthorn manages to outcompete native saplings in the struggle for light in shaded areas, and, because its berries are spread by frugivorous birds, new seedlings rapidly proliferate around a single parent. Unfortunately, although birds will eat the buckthorn berries, their nutritional value is minimal,2 and they contain a purgative toxin that further diminishes caloric uptake. For birds trying to fat load in preparation for the fall migration, the combined effects can be fatal. glossy buckthorn is not widespread in Eastman, but, where the native forest has been disturbed, it has gotten a foothold and become quite common. Merely cutting the saplings down only serves to turn them into vigorous bushes, but, fortunately, even large trees can be effectively killed with no damage to nearby native plants if the stump is immediately dampened with a herbicide, such as glyphosate. Perhaps the most thoroughly studied pesticide in common use, glyphosate appears to be virtually free of toxicity to humans and animals and, when applied carefully, innocuous to neighboring plants. Using a combination of this strategy as well as hand pulling seedlings, volunteers have greatly reduced the buckthorn infestation in the Heath property, and plans are being made to expand the effort to John’s glen this summer.
The most obvious invasive in Eastman is the common reed (Phragmites australis). until recent DNA analysis clarified the story, botanists had found its invasion difficult to understand.3 The species is known to be a native of North america and was used by native americans for thatch long before Europeans arrived. It is now believed that the European subspecies arrived here in the ballast of merchant ships in the 1800s and hybridized with the native species to create a new, much more aggressive variety. Today, the native subspecies has largely disappeared from New England leaving the new hybrid dominant. adapted to wetlands, tolerant of brackish water and excreting toxins that inhibit the growth of neighboring plants, its rhizomes are capable of spreading at a rate of 10 feet a year and reaching depths of six feet. Unbroken stands of Phragmites stretch for miles along the atlantic and great Lakes’ coasts. Not only do these monocultures of tall dry reeds along roadsides present a real fire hazard, but their impact on native wetland flora and fauna has been devastating.
In Eastman, significant stands occur in several places, the largest of which, measuring approximately one acre, lies to the west of Wellfield Road just south of Buck Common. Several methods to eradicate small infestations of Phragmites are being investigated, but these methods are not practical for large stands, for which herbicide spraying is recommended. The current plan is to begin by cutting and clearing the plants in the northern half of the Wellfield stand in mid-July. In September, after the Phragmites have regrown and bloomed, reducing the energy stores in the rhizomes, selective spraying with herbicide under a permit from the NH Department of Environmental Services is anticipated to kill 90-95% of them without significantly injuring the larger native plants within the stand. In 2015 and 2016, it will probably be necessary to repeat the effort on a smaller and more selective scale in order to eliminate the last individuals. In the meantime, depending upon the success of the initial effort, further cutting and spraying may be undertaken to expand the eradication effort.
We can never erase man’s footprint from the environment, but, together, we can do a lot to make life a little easier for our fellow species.
1. Executive order 13112, Feb. 3, 1999.
2. Smith SB, deSando Sa, & pagano T, The value of native and invasive fruit-bearing shrubs for migrating songbirds, Northeastern Naturalist, 20:171-184, 2013.
3. Saltonstall K, Cryptic invasion by a non-native genotype of the common reed, Phragmites australis, into North america. Proc. Nat’l Acad. Sci. 99:2445-9, 2002.
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