What Goes Into Controlled Burn?

The fires now ravaging North California have been particularly bad this year because years of drought have left the area much like a tinderbox.

Without sufficient rain for years, many plants have been left dry or dead, and brief periods of precipitation brought on a boom of growth then dried out again as summer wore on, according to a recent story by The New York Times.

One way to combat this build-up of “fuel load” is a controlled burn.

Stephen Mason, a graduate research associate and PhD candidate at the Academy of Natural Sciences of Drexel University, studies controlled burns and how they affect the environments where they’re performed. He explained how they generally work, what goes into deciding where they happen, and what happens afterward.

What are the benefits of a controlled burn?

Controlled burns are done for a lot of different reasons. One example is to reduce the forest fuel load to minimize the wildfire hazard. Fuel load, essentially, is the accumulation of leaf litter in a forest. Over time, the fuel load will build up, so when a wildfire does happen, the fire will be more intense since there is a lot of “fuel” to burn.

So, ironically, to prevent these intense wildfires from happening, trained forest fire professionals will set a controlled fire to purposely reduce the fuel load.

There are also different ecological reasons to do this. One example is that there are a lot of fire-dependent plant species that only will set seed and flower when a fire comes through. These plants have evolved to do this because there will be less competition and soils will be more nutrient-rich after a fire.

Another ecological purpose to do a controlled burn is to create different habitats, such as an open field for different species. Furthermore, that open field could be occupied by a non-native plant species and the best way to exterminate it is to set a controlled fire.

Are controlled burns done everywhere? Are there any spots locally that are good candidates for one?

Controlled burns are done in many places around the world for different reasons. There really isn’t a “best candidate” location for them. It really depends on who owns and/or manages the property and what goals they have.

Locally, Valley Forge National Historic Park is planning to do some controlled burns in the next couple of years for ecological purposes. Also, in the New Jersey Pine Barrens, controlled burns are frequently done to reduce the fuel load since they have historically been susceptible to wildfires due to its unique ecosystem.

How are spots chosen for controlled burns?

Spots are chosen depending on the goal of the owner or land manager. An example would be if a grassy field started to become a forest, but the land manager wanted to maintain the grassy field because different, rare species live in it. The manager’s goal might be to set a controlled burn every two or three years to make sure it maintains its current ecosystem for the rare species.

For different state forest fire services, the goal might be to do a controlled burn in an area over a regular time interval to keep the fuel loads at a certain level. If fuel loads exceed that level, a wildfire potentially could be harder to manage.

What happens to animals living in these areas during controlled burns?

The largest percentage of animals in these habitats would be insects. There are currently more than a million insect species known worldwide and a predicted 5 to 30 million to be discovered. Overall, we do not know how these animals are affected by fires at all since they are so diverse and have different roles in the ecosystem.

As an example, a mosquito will respond differently than a butterfly to a fire.

Animals that are large and charismatic, like mammals and birds will also behave differently When any disturbance occurs — like a controlled burn — it is assumed there will be “winners and losers” in that disturbance.

That might sound upsetting, but, on the flipside, there are many animals that would die without the fire. Thus, winners and losers in any circumstance.

How do areas where the controlled burns are performed recover afterward?

Depending on the perspective, the areas that had these burns did recover. There are numerous species that prefer dead wood, open habitats and the chance to live with less competition.

Having said that, every area will recover differently. It all depends on how intense the fire was, the habitat type, where you are in the world — say a rainforest versus the Canadian Arctic — the time of year during the fire, and a lot of other biotic and non-biotic factors.

Keep in mind, the land manager might not ever want the habitat to “recover” — assuming recovery means a mature forest. Many land managers actually burn different areas of their property at different frequencies. The idea behind this is to keep a mosaic landscape with different fire histories so different species can move around to a more favorable habitat.

Post by Frank Otto

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