Invasive plants are a side-effect of human activity: in the last couple of centuries the ease and speed with which humans can transport plants has outstripped the ability of the plant’s natural biological controls to keep up. Some plant species brought in by humans, typically for agricultural or horticultural purposes, are able to invade minimally managed wild areas and out-compete the native species. Problematic species tend to form dense monocultural stands.
Acton is in a ‘hot zone’ for the invasive plants of New England. This is because most of our land was cleared and stayed clear for much of the 18th and 19th century, when many currently-problematic invasive plants were brought in or were already present. Then, we had the return of forest with the abandonment of agriculture, and where that forest has been preserved against the press of development, many invasive plants have had a lot of time to spread.
And spread they have.
The Acton Land Stewardship Committee was chartered by the conservation commission in 1995 with looking out after Acton's 1600+ acres of town conservation lands. Our first few years were focused primarily on bringing parcels up to a common set of access standards: trails, blazes, signs, kiosks, bridges, boardwalks, and maps. As this big absorbing work has started to enter a maintenance phase, we are beginning to take on projects that include a wider view of what ‘stewardship’ means, including understanding the threats to biodiversity represented by invasive plants, and considering what to do about them.
One of our first steps in this direction was an invasive plants workshop we sponsored led by Chris Mattrick, then of the New England Wildflower Society (NEWFS) , in 2002. NEWFS has been an invaluable source of advice, information and encouragement since then.
This report is part of ongoing project to create a comprehensive prioritized plan for dealing with invasive plants on Acton’s conservation lands, species-by-species and parcel-by-parcel.
I spent some of 2005 walking the Acton conservation lands, marking up maps of where I’ve been able to see invasive plants. I am not a botanist, and I have only had minimal training, so I’m sure I have missed a lot. But the largest invasions are hard to miss, and the most common and problematic invasive species are easy to recognize after a small amount of training – their habit of forming dense masses makes them easy to spot.
These rough maps, with some extraneous notes on them, are here:
http://www.snyder-grant.org/Jim/Plants/invasives/ActonInvasivesMaps/index.html
The results are summarized in a chart in the next section
I plan to make the next version of these maps much more usable – as I resurvey I will be collecting GPS data so nicer maps can be generated automatically.
I also took some courses on making plans for dealing with invasives species, including specific treatments and over-all priority setting. This report is my first attempt to bring all of this information together – to describe what invasive plant species are where, and how we might prioritize a plan of attack against some of them.