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A controlled burn or prescribed burn ( Rx burn) is the practice of intentionally setting a fire to change the assemblage of vegetation and decaying material in a landscape. The purpose could be for forest management, ecological restoration, land clearing or wildfire fuel management. Controlled burns may also be referred to as hazard reduction burning , backfire , swailing or a burn-off.
Controlled burns are conducted during the cooler months to reduce fuel buildup and decrease the likelihood of more dangerous, hotter fires. Guidelines for Low Intensity Bushfire Hazard Reduction Burning Retrieved on 11-3-2009 Controlled burning stimulates the germination of some and reveals soil mineral layers which increases seedling vitality. In , controlled burns shift the species assemblage to primarily native grassland species. Some , such as those of lodgepole pine, sequoia and many chaparral shrubs are Serotiny, meaning heat from fire causes the cone or woody husk to open and disperse seeds.
Fire is a natural part of both forest and grassland ecology, and cultural burning has been used by indigenous people across the world for millennia to promote biodiversity and cultivate wild crops, such as fire-stick farming by aboriginal Australians. Colonial law in North America and Australia displaced indigenous people from lands that were controlled with fire and prohibited from conducting traditional controlled burns. After wildfires began increasing in scale and intensity in the 20th century, fire control authorities began reintroducing controlled burns and indigenous leadership into land management.
Furthermore, controlled fire can be used for site preparation when mechanized treatments are not possible because of terrain that prevents equipment access. Species variation and competition can drastically increase a few years after fuel treatments because of the increase in soil nutrients and availability of space and sunlight.
Many trees depend on fire as a way to clear out other plant species and release their seeds. The giant sequoia, among other fire-adapted conifer species, depends on fire to reproduce. The cones are pyriscent so they will only open after exposure to a certain temperature. This reduces competition for the giant sequoia seedlings because the fire has cleared non-fire-adapted, competing species. Pyriscent species benefit from moderate-intensity fires in older stands; however, climate change is causing more frequent high intensity fires in North America. Controlled burns can manage the fire cycle and the intensity of regenerate fires in forests with pyriscent species like the boreal forest in Canada.
Eucalyptus regnans or mountain ash of Australia also shows a unique evolution with fire, quickly replacing damaged buds or stems in the case of danger. They also carry their seeds in capsules which can be deposited at any time of the year . During a wildfire, the capsules drop nearly all of their seeds and the fire consumes the eucalypt adults, but most of the seeds survive using the ash as a source of nutrients. At their rate of growth, they quickly dominate the land and a new, like-aged eucalyptus forest grows. Other tree species like poplar can easily regenerate after a fire into a like-aged stand from a vast root system that is protected from fires because it is underground.
Prescribed fires are broadly used in the context of woody plant encroachment, with the aim of improving the balance of woody plants and grasses in shrublands and grasslands.
In Northern-India, especially in Punjab, Haryana, and Uttar Pradesh, unregulated burning of agricultural waste is a major problem. Smoke from these fires leads to degradation in environmental quality in these states and the surrounded area.
This review cites this research.
In East Africa, bird densities increased months after controlled burning had occurred.
To minimize the impact of smoke, burning should be restricted to daylight hours whenever possible.Guidelines for Low Intensity Brush Fire Hazard Reduction http://www.hillside.rfsa.org.au/lowintensityhrburn.pdf Retrieved on May 8, 2016 Furthermore, in temperate climates, it is important to burn grasslands and prairies before native species begin growing for the season so that only non-native species, which send up shoots earlier in the spring, are affected by the fire.
Head fires, that burn with the prevailing wind, are used between two firebreaks because head fires will burn more intensely and move faster than a back burn. Head fires are used when a back burn would move too slowly through the fuel either because the fuel moisture is high or the wind speed is low. Another method to increase the speed of a back burn is to use a flank fire which is lit at right angles to the prevailing wind and spreads in the same direction.
On the day of the controlled burn, personnel meet with the Burn Boss and discuss the tactics being used for ignition and suppression, health and safety precautions, fuel moisture levels and the weather (wind direction, wind speed, temperature and precipitation) for the day. On site, local fire control authorities are notified by telephone about the controlled burn while the rest of the team members fill drip torches with pre-mixed fuel, fill suppression packs with water and put up barricades and signage to prevent pedestrian access to the controlled burn. are canisters filled with fuel and a wick at the end that is used to ignite the lines of fire. Safe zones are established to ensure personnel know where the fire cannot cross either because of natural barriers like bodies of water or human-made barriers like tilled earth. , Japan]]During ignition, the Burn Boss relays information about the fire (flame length, flame height, the percent of ground that has been blackened) to the Communications Officer who documents this information. The Communications Officer relays information about the wind speed and wind direction so the Burn Boss can determine how the direction of both flames and smoke and plan their lines of fire accordingly. Once the ignition phase has ended in a section, the suppression team "mops up" by using suppression packs to suppress smoldering material. Other tools used for suppression are RTVs equipped with a water tank and a pump and hose that is installed in a nearby body of water. Finally, once the mop up has finished, the Burn Boss declares the controlled burn over and local fire authorities are notified.
The risk of fatal fires that stem from burning slash can also be reduced by proactively reducing ground fuels before they can create a fuel ladder and begin an active crown fire. Predictions show thinned forests lead to a reduction in fire intensity and flame lengths of forest fires compared to untouched or fire-proofed areas.
Fire suppression has changed the composition and ecology of North American habitats, including highly fire-dependent ecosystems such as oak savannas and canebrakes, which are now critically endangered habitats on the brink of extinction. In the Eastern United States, fire-sensitive trees such as the red maple are increasing in number, at the expense of fire-tolerant species like oaks.
In the 1970s, Parks Canada began implementing small prescribed burns however, the scale of wildfires each year outpaces the acreage of land that is intentionally burnt. In the late 1980s, the Ministry of Natural Resources in Ontario began conducting prescribed burns on forested land which led to the created of a prescribed burn program as well as training and regulation for controlled burns in Ontario.
In British Columbia, there was an increase in the intensity and scale of wildfires after local bylaws restricted the use of controlled burns. In 2017, following one of the worst years for wildfire in the province's history, indigenous leadership and public service members wrote an independent report that suggested returning to the traditional use of prescribed burns to manage understory fuel from wildfires. The government of British Columbia responded by committing to using controlled burns as a wildfire management tool.
With controlled burns, there is also a risk that the fires get out of control. For example, the Calf Canyon/Hermits Peak Fire, the largest wildfire in the history of New Mexico, was started by two distinct instances of controlled burns, which had both been set by the US Forest Service, getting out of control and merging.
The conflict of controlled burn policy in the United States has roots in historical campaigns to combat wildfires and to the eventual acceptance of fire as a necessary ecological phenomenon. Following colonization of North America, the US used fire suppression laws to eradicate the indigenous practice of prescribed fire. This was done against scientific evidence that supported prescribed burns as a natural process. At the loss to the local environment, colonies utilized fire suppression in order to benefit the logging industry.
The notion of fire as a tool had somewhat evolved by the late 1970s as the National Park Service authorized and administered controlled burns. Following prescribed fire reintroduction, the Yellowstone fires of 1988 occurred, which significantly politicized fire management. The ensuing media coverage was a spectacle that was vulnerable to misinformation. Reports drastically inflated the scale of the fires which disposed politicians in Wyoming, Idaho, and Montana to believe that all fires represented a loss of revenue from tourism. Paramount to the new action plans is the suppression of fires that threaten the loss of human life with leniency toward areas of historic, scientific, or special ecological interest.
There is still a debate amongst policy makers about how to deal with wildfires. Senators Ron Wyden and Mike Crapo of Oregon and Idaho have been moving to reduce the shifting of capital from fire prevention to fire suppression following the harsh fires of 2017 in both states.
Tensions around fire prevention continue to rise due to the increasing prevalence of climate change. As drought conditions worsen, North America has been facing an abundance of destructive wildfires. Since 1988, many states have made progress toward controlled burns. In 2021, California increased the number of trained personnel to perform controlled burns and created more accessibility for landowners.
In the north of Great Britain, large areas of grouse moors are managed by burning in a practice known as muirburn. This kills trees and grasses, preventing natural succession, and generates the mosaic of Calluna (heather) of different ages which allows very large populations of red grouse to be reared for shooting. The peat-lands are some of the largest carbon sinks in the UK, providing an immensely important ecological service. The government has restricted burning to the area but hunters have been continuing to set the moors ablaze, releasing a large amount of carbon into the atmosphere and destroying native habitat.
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