Invasive plant species, species that spread beyond a desired area having a harmful impact on the ecosystem, pose a growing threat towards the natural flora of national parks. Lack of disease and natural predators allow these species to thrive, especially in disturbed habitats such as roadways. At Weir Farm National Historic Site we are concerned with preserving the historical integrity of the property, specifically the natural landscape. Numerous management projects have been started to eradicate these invaders. Mechanical removal of plants is primarily done (hand pulling and use of weed wrenches) so as to impact the surrounding vegetation as little as possible. Roadsides are a prime location of invasives and these areas are frequently monitored and removal projects are done accordingly. There are also some well established invasive populations on the property and removals are done regularly, focusing on the outskirts of the infestation so as to try to stop further spreading throughout the park.
Preservation of natural resources condition is important to Weir Farm National Historic Site's managers. Through a partnership with the Northeast Temperate Network Inventory and Monitoring staff, park water quality, breeding bird abundance, and forest health are monitored on a regular basis. These three vital signs help the park to gauge any changes in environmental condition, and can alert managers of threats to the resources.