From the canopy to the understory, healthy forest ecosystems are made up of trees and plants of multiple species and age classes and the diversity of vegetation provides suitable and sustainable habitat for a rich and varied wildlife community. Forests that contain significantly high deer populations are vulnerable to excessive over-browse of young trees, shrubs, plants and other ground-cover. This excessive over-browse results in considerable negative impacts to overall forest health; including:
- reduced diversity in native plant and tree species (as deer leave behind only those species they prefer not to eat);
- increased spread of invasive plants that are resistant to deer browse;
- loss of tree species that serve as the next generation of tree canopy;
- increased susceptibility to environmental stresses, such as insect pests, severe weather-related disturbances, and climate change; and
- the destruction of vital habitat for insects, ground-nesting birds, and other wildlife.
Forests in Massachusetts are able to sustain deer densities below 20 deer/mi2. The Massachusetts Division of Fisheries and Wildlife (MassWildlife) also promotes a statewide deer management goal of 6 to 18 deer/mi2. Several deer abundance surveys conducted over the last seven years by DCR and MassWildlife found that the Blue Hills Reservation contains deer densities in excess of this sustainable threshold. While some areas of the Blue Hills have higher densities than others, the overall density estimate for the Reservation based on 2023 pellet count surveys exceeds 26 deer/mi2. Details and results of deer abundance surveying in the Blue Hills can be found below.