Firing Up Nature

How prescribed burns can increase public safety, improve habitat, and help restore the landscape.

Both instinct and education make us fear the destructive potential of flames. And our culture’s prevailing sense of what nature “should” look like – green and undisturbed – encourages us to see fire as the worst fate that can befall a natural area. So the idea of deliberately setting fire to the Vineyard’s iconic landscape takes a little getting used to.

Yet in recent years, columns of smoke from so-called prescribed burns, deliberately set for ecological purposes, have grown increasingly familiar to Vineyarders. The Martha’s Vineyard Prescribed Fire Partnership, a union of Island conservation organizations, conducts about a dozen burns annually, a number likely to grow in coming years. Conservation through combustion? One might reasonably ask what’s going on.

Perhaps surprisingly, the historical record, the existing vegetation, and multiple scientific studies all corroborate that fire has swept portions of the Vineyard repeatedly over the centuries – sometimes benign, sometimes horrific in scale and speed. One legendary fire in West Tisbury and Edgartown in May 1916 burned about a fourth of the Island’s land area in a single frightening day. (Evidence suggests that the hilly, up-Island moraine, with wetter soil types, has burned much less often.) Natural causes such as lightning strikes rarely start fires on the Vineyard, so human activity has presumably been responsible for most Island fires. But in any event, it is the relatively fire-free last seven or eight decades that are the aberration. And today’s deliberate burns reflect a growing consensus that the disappearance of fire from our landscape was a mixed blessing.

A fire-prone landscape

The southern and central portions of the Island occupy a geographical formation known as a sandplain: Formed by debris washing downhill as the glaciers that formed the Vineyard melted, our sandplain features dry mineral soils that offer little nutrition for plants. These conditions naturally foster hardy, drought-resistant vegetation.

This region is also prone to disturbances that influence plant life. Rugged, low-growing plant species are able to exploit opportunities in the wake of destruction, such as grazing, plowing, cutting of firewood, and high winds and salt spray from storms. All of these landscape disturbances produce many of the same effects, such as depriving woody plants of their investment in top growth, allowing more sunlight to reach low-growing plants, and releasing nutrients through the decomposition of downed vegetation.

But fire is a disturbance that produces unique effects though intense heat, the formation of chemical compounds, and a massive pulse of nutrients released through the burning process. Even a mild fire has a strong ecological impact, and some Vineyard habitats burn in ways that are far from mild. Over time, repeated burns give species that can tolerate fire an enormous competitive advantage; after centuries of recurring fire, unusual natural communities emerge, rich in organisms that have evolved the knack for turning a destructive force to their favor. The frequency and intensity of fire has varied widely from place to place, but across virtually the entire Vineyard sandplain, flames have left their mark.

Specifics of our fire history are harder to recover than this general picture. But the Island’s earliest residents likely knew, as commercial growers know today, that lowbush blueberries produce most heavily if burned every few years. Periodic fires would have enhanced the Island’s blueberry barrens, stimulating production of a food used by humans and game animals alike. Fire may have been used to clear underbrush to facilitate hunting. As agriculture grew more prominent in the culture of the Vineyard’s native population, fire was likely used to prepare or rejuvenate fields used for growing corn, squash, and beans – a technique that European settlers employed as well. And open fire used for any of a range of purposes surely sometimes ignited the sandplain’s flammable vegetation accidentally.

On the Vineyard, fire-adapted natural communities include grasslands along the southern shore (likely shaped by the combined influence of agriculture and frequent, low-intensity fires) and “barrens” communities farther inland, dominated by species such as pitch pine, scrub oak, and blueberry and derived from less frequent but more severe burns. Barrens communities dominate much of Manuel F. Correllus State Forest and Long Point Wildlife Refuge in West Tisbury. Associated with – and often eating – these characteristic plants are equally specialized insects, which, like fire-adapted plants, have evolved traits that help the species, if not always the individual, persist in the face of recurring fire. In particular, the Vineyard is renowned among biologists for its rare, specialized, barrens-dwelling moths, especially moths that associate with scrub oak, a rugged, bush-like relative of the better-known tree oaks.

Adaptation to fire can take many forms in plants. Some simply shrug off any kind of disturbance, fire included. A massive root system, for instance, allows little bluestem grass to bounce back in the wake of burning, grazing, or mowing. Some plants resist the direct effects of fire. The thick bark of many oak species, for example, insulates the tender underlying tissues that transport water and sap. Other plants may lose their top growth to a burn but retain the ability to regrow. Pitch pine and scrub oak – and other fire-adapted trees of dry, sandy soils – burn violently but re-sprout almost immediately. Other plants rely on fire to promote the release or germination of seeds; heat can scarify thick seed coats, or chemicals in smoke can stimulate the development of plant embryos. And for some other native plants, like wild indigo and New England blazing star, fire helps control insects that would otherwise prey heavily on their seeds.

Whatever the mechanism, a burn leaves fire-adapted plants poised for quick regrowth, amid suppressed competition and a bounty of nutrients released by the fire. Indeed, these plants typically don’t just tolerate burning, they encourage it, often producing flammable oils or growing in a bushy form that effectively mixes fuel and air. The evolutionary logic is simple: If fire hurts you less than it hurts your competitors, more fire is better.

Reducing wildfires

The historical record of the early twentieth century shows that fires of a thousand acres or more swept the sandplain every few years. But as mid-century neared, fires grew less frequent, with agriculture making less use of deliberate fire and the human community relying less on open flame as a source of energy. During and after World War II, when the Island hosted a substantial military presence, more organized and better-equipped fire departments quickly suppressed most wildfires. Moreover, as more and more of the Vineyard succumbed to development, the incentive for fire suppression increased: Letting a fire run its course on an expanse of wasteland ceased to be an option.

No doubt the decreasing frequency of major fires registered as progress to Islanders of the mid-twentieth century. But unanticipated drawbacks began to emerge. One change was a decline in the Island’s characteristic wildlife. In an elegant study conducted in 2000, Adam Mouw, then a biology graduate student at the University of Massachusetts, compared aerial photographs taken of the center of Martha’s Vineyard in 1938 with a similar set of photos from 1985. Identifying the vegetation types shown by the photos and measuring the areas covered by each type, he demonstrated a fifteen-fold increase in the amount of mature woodland over the intervening years, at the expense of acreage covered by scrub oak and young woodland. In essence, large sections of the state forest lost their distinctiveness, coming to resemble ordinary woodlands elsewhere in the region that lack a significant fire history.

A half-century of fire suppression, in other words, dramatically reduced the habitat available for the Vineyard’s specialized, fire-adapted wildlife, rendering already scarce species even more rare. Restoring these populations was the original motive for prescribed fire here. “It’s hard to state how important the Vineyard is to the state’s overall biodiversity,” says Tim Simmons, a restoration ecologist with the state’s Natural Heritage and Endangered Species program and one of the earliest proponents of fire management on the Vineyard. “And it is largely fire that accounts for that importance.”

But the disappearance of fire on the landscape also had implications for the Vineyard’s humans. As the Island’s history of fire faded from the communal memory, hundreds of houses were built in barrens habitat, areas that had burned repeatedly over past centuries. As decades passed without major fires in those areas, vegetation continued to grow, with each season’s increase in plant material representing more material that could burn if a fire ever got out of control. On a dry, windy day, the concern is that a small fire in an overgrown area could spread explosively, sprinting downwind as embers blow ahead of the flames. As such a fire expands, it produces strong updrafts that suck more air into the flames, launching a spiral of intensification.

The notion of wildfire ripping through a residential subdivision may call to mind California canyons rather than our homey little sandbar. But a major fire here probably only requires a little bad luck: a warm, windy day, say, in spring before the vegetation greens up, a fire that starts in a remote area, and perhaps an untimely miscommunication or equipment failure. Siting extensive residential development among highly flammable vegetation was, to put it bluntly, a bad idea. But the Island’s pattern of development is unlikely to change, and hence fire practitioners are looking for ways to help reduce the hazard posed by overgrown vegetation. Ironically, fire itself – applied carefully, under controlled conditions – has emerged as one strategy to reduce the risk of random, possibly catastrophic burns.

Reigniting a process

Following a multi-year campaign to improve the fire lanes in the state forest, the Massachusetts Department of Conservation and Recreation (DCR, which manages the forest) has teamed up with Island fire departments and the Vineyard Prescribed Fire Partnership in a program of brush cutting and prescribed burning along the northern and eastern edges of the forest. (Historically, these have been the downwind sides when major wildfires have occurred.) Drawing on federal grant programs for controlling wildfire hazards, DCR and its partners seek to reduce the amount and volatility of fuels on hundreds of acres per year in the state forest, reports Aaron Whiddon, an acting district fire warden with DCR. He says the treated areas would “provide a buffer zone [to fight] any fire coming out of the state forest,” reducing the fire’s intensity and creating safer conditions for firefighters to work in if necessary. Most of the prescribed fire that DCR initiates throughout the state is aimed primarily at enhancing public safety, but Aaron stresses that such burns also represent sound ecological management, “accomplishing two objectives in one operation.”

Fire-adapted landscapes are common across the world, and the Vineyard is by no means the first where burns suddenly grew less frequent. Accordingly, over the last fifty years or so, the science of safely returning fire to those areas has steadily developed. Today, literally millions of acres of land are deliberately burned each year across the United States, mostly in western and southern states, for reasons including fuel reduction to reduce wildfire risk, suppression of harmful insects, and habitat improvement. Fire-related research is a burgeoning discipline within the field of ecology, and the training of burn crews and the development of plans for prescribed burning have become professionalized.

The process of prescribed burning begins with the identification of areas where vegetation shows the influence of past fires and a burn can be conducted with acceptable levels of risk and inconvenience. On the Vineyard, grassland and shrubland along the south shore have been the main focus of prescribed burning: Katama Air Park in Edgartown has seen burns almost annually since the site was protected for conservation in the 1980s, extending decades of less formal burning that kept vegetation low around the runways. In recent years, prescribed fire has also been applied to wooded habitat on the sandplain in the Island’s interior, with burns often preceded by brush cutting in order to reduce the volatility of the woody fuels.

In the first years of prescribed fire on the Vineyard, burns were alarmingly casual affairs; veteran land managers recall early ecological burns at Katama at which the crew, largely untrained, showed up in jeans and tennis shoes. Current methods are much more rigorous. Burn crew members undergo extensive training and use flame-resistant clothing, radios, and specialized equipment. Burns are meticulously planned, supervised by experienced “burn bosses,” and limited to times when temperature, humidity, and moderate wind minimize the chances of intense fire. Small fire engines stand ready on-site, and close coordination with Island emergency services keeps the public informed and backup available.

As alarming as fire can be, ultimately it obeys the laws of physics. Deprived of fuel or oxygen, it goes out; deprived of an ignition source, it never starts. Fire practitioners exploit these basic truths to control a prescribed fire. Typically, a fire crew begins a burn by carefully setting fire to the downwind side of the chosen area. Spraying water or raking away any flammable plant material on the downwind edge, crew members prevent the fire from moving outside the area but allow it to creep upwind.

When a sufficiently broad strip has been burned along the downwind edge, the crew can move into the area and light a “head fire,” which moves downwind until it hits the previously burned area, where all the fuel has been exhausted. This description is oversimplified, of course: Numerous precautions are taken to keep the fire from escaping, and a crew can vary the process to achieve particular effects (minimizing smoke production, for example, or producing a slow-moving fire to maximize ecological effects). But this basic idea – using carefully pre-burned areas to limit where the main fire can go – is a key tactic.

The likelihood of a catastrophic wildfire on the Vineyard may be low in any given year; our last truly major example was a 1,200-acre fire in Edgartown in 1965. Sources of ignition that could start a wildfire are not numerous on the Island today. Moreover, we are protected by proficient and closely cooperating fire departments. Still, unintentional fires continue to occur almost annually. And our soil types, weather patterns, and vegetation all ensure that the tendency of our sandplain to burn – and hence the possibility of a major wildfire – will never entirely fade. Meanwhile, an important part of the Island’s heritage is our rare wildlife, much of it established by and dependent on a regime of repeated fire.

Deliberate fire is not without risk. Effects like smoke and blackened vegetation challenge the community’s aesthetic sense. Fire can be expensive to apply, and ideally it must be applied repeatedly, at intervals of several years, in perpetuity. But despite these challenges, a strong case can be made that fire, carefully used on a large scale at appropriate frequency, is what the Island’s sandplain really wants – an ancient process that renews distinctive habitats, encourages rare species, and limits the accumulation of fuel. As strange as it may sound, the Vineyard’s fiery past may provide a road map to a future that is both ecologically sustainable and safer for the human community.