Three Island towns — Chilmark, Edgartown, and West Tisbury — are at especially extreme risk of wildfire, according to a recent and long-awaited report by the Martha’s Vineyard Commission on wildfire risks and remedies for Dukes County.
Rife with maps, tables, and modeling, the 254-page “Dukes County Wildfire Protection Plan” illustrates where wildfire hazard areas are across the six towns of the Vineyard and on the Elizabeth Islands. A major component of the plan is a Vineyard map that paints large areas of Chilmark. Edgartown, and West Tisbury red to denote “extreme” wildfire risk. Conversely, Vineyard Haven and Oak Bluffs sport some of the largest concentrations of green on the map, denoting low wildfire risk. The composite map takes into account fuel loads, weather, past wildfires, the anticipated rate of fire spread, community proximity to vegetation (wildland urban interface), topography, and the potential for treetop fires, known as crown fires.
The overall plan recommends a number of actions be taken to offset the risk of wildfire. These include the reduction of fuel loads and the increase of fire breaks, roadway improvements, new bylaws to ensure safety zones or “defensible space” around properties, more water storage tanks, acquisition of smaller firefighting vehicles, community education, and the recruitment of new firefighters.
The plan warns that wildfires in the county should not be underestimated based on their historical infrequency, nor should they be discounted in scale when compared with wildfires that beset the Western U.S.
“Fire history within Dukes County is limited, but that does not mean fires are not severe,” the plan states. “Sixteen fires occurred between 1867 and 1929, each burning more than 1,000 acres.” Nearby on the Cape, in similar habitat to the Vineyard, the plan mentions the 1957 Carver fire that consumed 18,000 acres before Cape Cod Bay snuffed it out. It was estimated to have burned at 53 acres per minute.
The “most recent” county fire (1967) burned 1,200 acres, according to the plan.
“While these fires may seem small compared with fire activity in the Western U.S., it is important to consider these fire sizes in relation to the size of Dukes County at 66,080 acres. While the Northeast experiences decreased fire frequency, fires can be equally as destructive as the more well-known Western fire occurrences. Most of these historic fires in the county have occurred on Martha’s Vineyard in close proximity to roadways, the Manuel F. Correllus State Forest, and more populated areas such as Vineyard Haven. Less populated areas, the Elizabeth Islands and western Martha’s Vineyard, in contrast, have received very low numbers of fires over the past century.”
Rate of fire spread analysis and estimation was conducted for all six Vineyard towns. This rate is presented through units called “chains” at one-hour intervals. One chain equals 66 feet. Chilmark was calculated to have the most extreme spread potential. The town was estimated to have 52.16 percent risk of wildfire moving at 50 or more chains per hour (3,300 feet plus per hour). Edgartown had the second most extreme risk for a 50-plus chain rate — 51.16 percent. Oak Bluffs presented the lowest potential for extreme spread at 18.71 percent.
The most probable direction of wildfire movement is anticipated eastward, based on wind patterns. “The county lies within the prevailing westerlies,” the plan states, “with the predominant wind direction from west to east.”
The plan notes that the types of fuels inherent to the county are at times susceptible to “extreme fire behavior.” The dry or “xeric” nature of the vegetation contributes to this susceptibility. The different heights certain Island vegetation grows to can create the potential for a ladder effect, whereby flames climb up to the treetops, creating crown fires. These fires are very difficult to suppress.
Edgartown Fire Chief Alex Schaeffer, one of the contributors to the Dukes County Wildfire Protection Plan, told The Times aircraft such as Canadian air tankers would be required to fight a crown fire.
“All of Dukes County is classified as Atlantic Coastal Pine Barrens,” the plan states. “Because soils in this ecoregion are sandy, acidic, and extremely porous, the soil loses moisture rapidly. Under certain conditions, these vegetation communities can support extreme fire behavior. Within pine barren systems, the overstory is dominated by pitch pine (Pinus rigida), while the understory is composed of scrub oak (Quercus ilicifolia) woodlands, shrublands, and heath species. Other common species within this ecoregion include ericaceous shrubs such as huckleberry (Gaylussacia spp.) and blueberry (Vaccinium spp.), which produce volatile substances from leaves and stems. This increases flammability and contributes to fire spread. The combination of xeric vegetation and ladder fuels, such as scrub oak, can lead to crown fires.”
The plan pays close attention to the “wildland urban interface” (WUI). This is described as areas “where human habitation and development meet or intermix with wildland fuels.” Interface areas are defined as places where development abuts or is near to “continuous vegetation.” Intermix areas are defined as places where development is spread through wildland, and covers less area than the surrounding wildland. Dukes County is described as a combination of the two types.
“The WUI creates an environment in which fire can move readily between structural and vegetative fuels, increasing the potential for wildland fire ignitions and the corresponding potential loss of life and property,” the plan states.
West Tisbury was found to be the leader in land classified as wildland urban interface, with 82.57 percent. Tisbury had the second most at 70.24 percent. The other four towns all came in at over 50 percent: Edgartown 69.80 percent, Aquinnah 68.64 percent, Oak Bluffs 66.44 percent, and Chilmark 64.93 percent.
The plan outlines steps homeowners can take — steps officials can recommend as part of outreach efforts — to diminish the dangers posed by wildfire. Ranking high among those steps are measures to create “defensible space” at a 30-foot minimum protective zone around a dwelling. Creation of such a zone includes removal of heavy foliage immediately around the structure, and pruning work further out.
“Within the minimum 30-foot safety zone, plants should be limited to fire-resistant trees and shrubs,” the plan states. “Focus on fuel breaks such as concrete patios, walkways, rock gardens, and irrigated garden or grass areas within this zone. Use mulch sparingly within the safety zone, and focus use in areas that will be watered regularly. In areas such as turnarounds and driveways, nonflammable materials such as gravel are much better than wood chips or pine needles.”
The plan recommends eliminating ladder fuels. “All trees within the safety zone should have lower limbs removed to a height of 6-10 feet,” the plan states. “Remove any branches within 15 feet of your chimney or overhanging any part of your roof. Ladder fuels are short shrubs or trees growing under the eaves of the house or under larger trees. Ladder fuels carry fire from the ground level onto the house or into the tree canopy. Be sure to remove all ladder fuels within the safety zone first. The removal of ladder fuels within about 100 feet of the house will help to limit the risk of crown fire around your home.”
For firefighter and apparatus access, the plan also recommends driveways be “uncluttered and at least 12 feet wide” and sloped under 10 percent grade.
“Trim any overhanging branches to allow at least 13.5 feet of overhead clearance,” the plan states. “Also make sure that any overhead lines are at least 14 feet above the ground. If any lines are hanging too low, contact the appropriate phone, cable, or power company to find out how to address the situation. If possible, consider a turnaround within your property at least 45 feet wide. This is especially important if your driveway is more than 300 feet in length. Even small fire engines have a hard time turning around, and cannot safely enter areas where the only means of escape is by backing out. Any bridges must be designed with the capacity to hold the weight of a fire engine.”
Plan project manager Dan Doyle told The Times fire protective steps outlined in the plan have value for most everyone, not just for folks who live in WUI areas. However, he said there are “higher stakes” for those who do live in WUI areas.
Chief Schaeffer described the overall plan as an effort to make wildfire mitigation and response manageable given the “very limited means” available on-Island.
Doyle said the plan was made possible by a Federal Emergency Management grant administered through the Massachusetts Emergency Management Agency. Doyle tipped his hat to former MVC staffer Jo-Ann Taylor, who secured the grant. The MVC also contributed funding, Doyle said, as did a number of Vineyard land conservation organizations. The MVC will host a community input session Friday at noon regarding the plan. Another session is slated for Sept. 30 at 5 pm. The Zoom information will be available later this week at the commission’s website.
“I’m hoping to hear people weigh in,” Doyle said.