Tourists aren’t the only ones who love the Massachusetts coast. Overabundant deer on sand dunes and salt marshes can have surprising and serious effects on these unique habitats.
When most people think about ideal white-tailed deer habitat, they think of forests and fields. However, deer can thrive in coastal areas with few trees in sight, living comfortably among beach dunes and salt marshes. Deer are even fantastic swimmers, often seen swimming among the Boston Harbor Islands, within the Cape Cod Canal, and along the Elizabeth Islands, Martha's Vineyard, and Nantucket.
When deer populations grow too large in coastal habitats, it can come at a significant cost to the local ecosystems. In areas like Nantucket and Martha's Vineyard where there are no natural predators and limits on hunting, densities can exceed 100 deer per square mile.
Adding to coastal erosion
According to the Massachusetts Office of Coastal Zone Management and the U.S. Geological Survey, approximately 68% of the Massachusetts shoreline is currently experiencing long-term erosion driven by climate change, with some vulnerable areas losing up to 12 feet of coastline per year. Erosion leads to habitat loss and immense economic consequences for coastal communities. Unfortunately, deer activity can also exacerbate coastal erosion.
Coastlines are dynamic, but they rely on vegetation to stabilize them. Overabundant deer strip away beach grasses through browsing, bedding along the beaches, and movement along deer trails. These coastal plants are critical for slowing erosion by stabilizing sand dunes. Without the stabilizing roots, winter storms, high tides, and powerful winds can quickly blow the sand away. Natural deer behavior further compounds these issues along cliff-side edges, where compressed deer trails become new cleave points for whole sections to collapse onto the beaches below.
Changing hydrology in salt marshes
Salt marshes act as a natural buffer against coastal erosion with interwoven root systems locking fragile sediment in place while thick surface vegetation absorbs and dissipates waves and storm surges. Each salt marsh maintains a local hydrologic cycle of flooding and draining during tides and storms as ocean waters come in and out. These hydrology cycles are critical for delivering essential sediment for building/maintaining elevation, flushing toxic soil byproducts, and maintaining salinity balance that native, soil stabilizing grasses require to survive.
Along Martha's Vineyard and many southeastern Massachusetts coastal communities, high deer abundance is changing the local hydrology. Heavily used deer trails compact marsh soil and lead to a loss of critical vegetation and its roots. This compaction reduces the marsh's capacity for water absorption during daily tide cycles and exposes sediment to erosion, allowing it to wash away with receding tides and storms.
Impacting local biodiversity
The fragile maritime ecosystems of the Massachusetts coast provide an irreplaceable refuge for rare flora and act as a vital corridor for migratory birds. However, overabundant deer threaten the resilience of these habitats, causing cascading harm to the wildlife they contain.
Beyond habitat loss due to coastal erosion, deer directly affect vulnerable plants and animals. Deer are browsers and tend to prefer native plants, including the endangered lion's foot plant, a favorite food of deer found on both Martha's Vineyard and Nantucket. Intense grazing and soil mixing from deer movement can prevent native marsh grasses from recolonizing disturbed areas, locking the ecosystem in a damaged state that favors the Eastern mud snail, a nuisance species that thrives in degraded habitat. Excessive deer activity along beaches and in salt marsh areas can also threaten birds, like endangered roseate terns and saltmarsh sparrows, by trampling nests, exposing nests to predators, or even predating on the nests themselves while opportunistically browsing.
Taking action
Addressing overabundant deer in coastal communities is a complex issue that requires collaboration to increase the harvest of deer through legal, regulated hunting.
Increasing the donation of harvested deer to MassWildlife's Hunters Share the Harvest program has been one successful approach to reaching new record deer harvests while also addressing local food insecurity. Through partnerships with the Martha's Vineyard Island Grown Initiative, MV Hunt Club, Nantucket Land Bank, Nantucket Food Pantry, and Nourish Nantucket, an astounding 14,000 meals were distributed during the last hunting season to local families in need. Martha's Vineyard led the state, with more than 11% of all harvested deer being donated.
Expanding hunting opportunities can also increase the deer harvest. Through recent regulatory changes, MassWildlife expanded deer hunting seasons in many coastal wildlife management zones.
Local communities can also play a role by opening more municipal land to hunting, removing bylaws for written permission or implement restrictions, and welcoming hunters onto private property. Increasing hunting access is the most efficient tool to manage deer populations and restore ecological balance.