Aerial drops of fire retardant on wildfires are one of the most dramatic images of firefighting. But critics cite high cost, limited effectiveness and potential harm to fish.

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Hundreds of thousands of gallons of chemical fire retardant were dumped from planes all over wildlands in Washington last fire season, more than almost anywhere in the West. And this summer’s even bigger fire season could see just as much of the crimson chemical slurry dumped on the landscape, if not more.

Retardant can save human lives, property and wildland habitat.

“It is a very important tool in the toolbox, for sure,” said Beth Lund, an incident commander with the U.S. Forest Service and veteran of 40 fire seasons, including the 110,000-acre Canyon Creek wildfire near John Day, Ore., this past summer. But fire retardant, she cautioned, is not a silver bullet.

“You always have to follow up with boots on the ground,” Lund said. “It doesn’t put the fire out. If you don’t follow it up, and just drop retardant, that is when it is not effective.” Aerial retardants are wasted in fires too big to quickly get crews into, or on terrain too rugged, or in winds too high and hot for the chemicals to even hit the ground, Lund said. “You get a fine mist.”

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It also is a mistake to rely on aircraft, she cautioned, which can be fickle. “If the winds are too swift they can’t really fly, it’s not effective and it’s dangerous.”

Michael Medler, an associate professor in the department of environmental science at Western Washington University, says the environmental damage and the inappropriate use and overuse of aerial retardants concern him.

Medler recently testified before the U.S. Senate that the better approach to fighting fire is to create defensible space around towns adjacent to wildlands, rather than attacking every fire with every tool firefighters can throw at it — including copious use of aerial fire retardants.

“I am not anti-tanker,” said Medler, a former firefighter. Fire retardant can be “magic,” he said. But it has to be used strategically and carefully, he said.

“Sometimes it’s a great tactic. Sometimes, you are just painting stuff red.”

Often too late

An analysis of the use of aerial retardant, led by David Calkin, a research forester in the Rocky Mountain Research Station of the U.S. Forest Service in Missoula, Mont., found the agency lacks the data to assess the cost-effectiveness of aerial firefighting tactics, which accounted for $1.6 billion, or more than a quarter of the total $6.1 billion cost of firefighting for the Forest Service nationwide, from 2007 to 2011.

The team, which published its results in the International Journal of Wildland Fire last year, also found that despite agency guidance to use the airdrops of retardant primarily in initial attack, about half the time the retardants were used in larger fires. Further analysis showed that most of those fires escaped anyway.

Yet the escape rate was as low as only 2 to 5 percent when aerial retardant was not used. That indicates airdrops are possibly happening when the fire is already beyond the capacity to control.

“We are arriving at a time when our ability to stop it has crossed a threshold,” Calkin said in an interview. “We are using them for the most challenging fires, and frequently the fires, despite our best efforts, escape.”

The Forest Service is in the midst of a multiyear study to analyze the use and effectiveness of the retardants, Calkin said. “We need to use them where their use is most effective and reduce the uses when the conditions aren’t right.”

Aerial fire retardant is an alphabet soup of chemicals, comprised mostly of water, ammonium phosphate fertilizers, colorants, corrosion inhibitors, thickeners, stabilizers and bactericides.

Retardant is meant to be dropped on the edge of whatever firefighters are trying to protect, or in front of an advancing fire, to slow and calm it. The dramatic red color is used to help pilots see where they have already dropped the chemicals.

A risk to fish

After years of legal battles, the Forest Service in 2011 completed stiffer guidelines for use of the retardant, outlawing spraying the chemicals within 300 feet of water bodies, except when human lives or public safety were at risk and aerially delivered retardant could be reasonably expected to alleviate the threat.

As fires raged in North Central Washington this summer, some tributaries of the Twisp River — home to endangered and threatened chinook salmon — ran red with retardant. While the effect on those runs is not yet known, fire retardant can kill fish.

“It has been shown to be lethally toxic to chinook in our studies at concentrations less than what the manufacturer recommends,” said Joseph Dietrich of the National Oceanic and Atmospheric Administration Fisheries’ Newport, Ore., office.

In lab tests, some chinook died within 96 hours of exposure. Others died later, when their ability to transition from fresh water to salt in their migration to the sea was damaged by exposure to the retardant. In each case, ammonia was the problem, damaging the animals’ gills and disabling their ability to absorb oxygen.

“How do we translate what we see in the lab to what we see in real life, that is the big unknown,” noted Shirley Zylstra, program leader for wildland fire chemicals for the Forest Service in Missoula. Toxicity would depend on the actual field conditions, the life stage of the fish, and dilution from stream flow, she said.

Over the past four years, the Forest Service has dumped an average of 9 million gallons (approximately 5,111 aerial drops) of fire retardant on National Forest System lands, according to Jennifer Jones, agency spokeswoman.

Of those, less than one-half of 1 percent — or 25 per year — occurred within or partially within a waterway. Many of those consisted of a light mist or drift of retardant as aircraft completed their drops, Jones said.

On two occasions in the past four years, dead fish were documented, but only a few. It was unknown if there were more dead fish not documented, or if the cause of death of those seen was fire retardant, elevated water temperatures or other fire-related causes.

None of the deaths involved a threatened or endangered species, Jones said.

Pressure to fly

If anything, says Lund, the incident commander, she is usually under pressure to use more retardant, not less. Communities with fire threatening homes want desperately to see a response — and planes in the air is what they can see.

“They think we are not doing anything if we don’t have stuff buzzing around in the air; they don’t see the 600 people on the ground. There is huge pressure in those communities. Are we doing it just to appease those folks? I am mindful that I am in charge of taxpayers’ dollars and we use retardants when it helps the strategy to keep it from getting to the next subdivision.”

In her 40 years fighting fires, defending homes in the backcountry is a new and sometimes impossible challenge. “People have built out in the wildlands that have no defensible space. They still have firewood on a wooden deck creating a ladder right to the eaves, and pine needles on shingle roofs,” Lund said.

Better, however, Lund said, would be people seeing to the safety of their homes. “People are not taking responsibility. They want to live in nature, but fire is part of nature. I would change the way people and county commissioners allow people to build with nonfire-wise material, with no regard for defensible space.”