I have been working as a volunteer trail steward for the Lake George Land Conservancy for over six weeks now and I love it! One of my responsibilities is to keep an eye out and destroy any invasive plant species that may invade the preserve. The LGLC has compiled a list of the top five most invasive plant species in our area and the list is at:
http://www.lglc.org/media/Terr-inv-chart.pdfRight now purple loosestrife and shrubby honeysuckle are the two that I have seen and have had to deal with the most. The LGLC prints the brochure that I have linked to above and distributes them in their trail kiosks and also is making a concerted effort to educate homeowners as to the benefits of removing invasive plants and planting native plants on their properties.
You should read the brochure that I have linked to see the problems and issues regarding these plants and most importantly what you can do about them. Also, these are the top five most invasive plant species in my area. You should look to see what plants or animals for that matter are invasive problems specific to your region. One of the main problems with invasive species is they tend to out compete native plants or animal and can have an impact on other parts of the ecosystems. For instance, the fruit of shrubby honeysuckles tend not to have enough protein for migratory birds that feed on them and may impact their migratory success rate.
I know that many of us letterboxers and geogachers like to do things that shine a favorable light on our hobby. I think that if you educate yourself on this problem and then find a way to take some action in your area. Being out in the parks and nature trails as we are we can be the eyes for those who would like to remove and mediate the impact of these plants and animals. Do not cut or remove any plants on public or private property unless you have permission. One thing that you can do is contact those in charge of the property and tell them where the infestation is and if you could help in any way. Make sure you obtain permission first before you act on the ground.