Removing Invasive Plants Makes a Difference

Many of us have worked on invasive plant removal projects from time to time. It’s a satisfying experience to see a choked woodland opened up to opportunities for native plants to return and thrive. We don’t often get the opportunity to see the benefits of the removal, particularly on insect populations, but we hope and trust that nature will rebound. Recently, a friend shared a link about a study completed in 2013 in four areas “within the Oconee River watershed in Northeast Georgia that were heavily infested with Chinese privet.” The results were just what you hoped they would be: “These findings provide justification for allocating resources for invasive shrub species removal to support long term conservation of these important insect groups and the ecological services they provide.”

Privet (Ligustrum sinense) thicket at a stream

Privet (Ligustrum sp.) is a serious invasive pest in the Southeast, with large populations in forest land (over 1 million hectares in 2008) as well private land and roadsides. Another upcoming invasive shrub in my area is Elaeagnus sp., and I’m starting to see very dense thickets of it forming where humans take no action to control it. Both of these affect the amount of light and open ground (for nesting bees) in an area and reduce the amount of sunlight available to native herbaceous plants, reducing the diversity of plants and pollinators.  There are some who would argue that privet flowers themselves support bees, but “Although privet may be an abundant floral resource in late spring, heavy infestations with dense shrub canopies severely limit abundance and richness of pollinators by decreasing availability of sunlight.”

I am including some of the interesting parts of the study; feel free to read it directly at the source here. The detail, resources, and references are worth exploring.

The study measured pollinator populations 5 years after removal of the privet in the study areas (completed by 2007 after cutting in 2005 and treating sprouts in December 2006); the study was completed in 2012. The study areas differed on how the privet was removed: by either mechanical mulching or hand-felling. The sampling method for this study is described as: “Bees and butterflies were sampled for one week out of each month from March to October 2012 on mulched, hand-felling, control, and desired future condition plots.”  The information collected in 2012 was compared to a previous study in 2007 on the same plots. “This is the first study showing that these immediate responses of the pollinator communities to disturbance continue for at least five years despite secondary plant succession.”

So for those of you out fighting the good fight – keep fighting. It’s worth it to the creatures that need us the most.