Happy New Year! I hope everyone had restful and enjoyable holidays. In addition to looking back over the year that just past, a common New Year’s tradition is to make predictions for the coming year. Without going too far out on a limb, one of my predictions for the upcoming year is that the debate over invasive plants will continue to intensify, especially as it relates to Landscape Horticulture. Along these lines, a couple of recent articles by Gregorio Gavier-Pizarro and his colleagues at the University of Wisconsin and the USDA Forest Service caught my eye.
In both studies; “Housing is positively associated with invasive exotic plant species richness in New England, USA” (Ecological Applications 20:7, 1913-1925) and “Rural housing is related to plant invasions in forests of southern Wisconsin, USA” (Landscape Ecology 25:10, 1505-1518), the investigators conducted on-ground assessments of species richness and density of commonly listed invasive plants (e.g., Japanese barberry, Autumn olive, Honeysuckle, Common buckthorn, Multiflora rose) in conjunction with spatial analysis of remote sensing data to examine patterns of invasive spread in the urban/wildland interface. As one would expect, the presence and species richness of the invasives increased with development. An important ‘take home’ message, however, is that disturbance associated with rural housing development and the creation of edges appears to be the biggest driver of invasive species encroachment. That is, land clearing, road-building and other development activities create habitats that are more susceptible colonization – a condition referred to as ‘invasibility’. So whether a particular homeowner plants natives or non-invasive exotics they may still contribute to the expansion of invasive exotic plants in their region by increasing its invisibility.
The other thing that makes this work and related studies significant is that I think we will see a continued shift in the efforts to curtail the expansion of invasive exotic plants. In particular, rural housing development and associated landscape practices will become and increasingly intense front-line in the invasive battle.
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Gotts love it. Back in the 80s I was phone interviewed (as a state forester) by a local yuppy type magazine about threats to our local forest ecosystems. I vaguely knew the reporter and where she lived… in one of those forest encroaching sub-divisions. Her primary question was…’In your opinion, what is the largest threat facing our forests in the S Valley. My response was a very affirative ‘I believe the biggest threat our forests face is human encroachment… some such’ She was obviously expecting something like acid rain (that was big back then) or maybe the impending gypsy moth invasion. A
nyway, there was a long pregnant pause…. and the a drawn out ‘ohhhh? And what do you mean by that?’ I proceded to outline how human developments were fragmenting the forest mass and opening up avenues for invasive species and breaking up wild life habitat and creating conditions conducive to invasion by Ailanthus, mulberry etc. At the time I think I also used the brown cowbird as an invasive example… Anyway the effect of cowbird nest invasion on neo-tropicals was fresh in my mind, so… Well, my interview never got into the article which was mostly about the threat of acid rain and the dirty industrial mid-west dumpin on us here in the east. Meanwhile the edges of our Allegheny and Blue Ridge forest cohorts continue to be fragmented by housing developments. I have no doubt if the same type of study were run here in Virginia, we would see pretty much the same correlation.
It seems to me that the best way to minimize the impact of already in place developments is to educate people on how to best limit exotics and invasives, a tough nut to crack when so many of these plants are for sale at big box stores and many nurseries.