On a screen, wildfire ecologist Bob Gray showed his audience a pair of before-and-after photos.
One was taken from a fire lookout tower in Washington in 1938. It showed a varied forest landscape, with recent burns, older burns, logged areas, and different stages of regeneration, along with some old-growth forest and areas of deciduous trees.
"When fires occurred in that landscape, they were small," Gray said during a presentation June 26 in Taghum. "They didn't get big because there wasn't contiguous fuels. There was vegetation there that acted as speed bumps for the fire.They basically impeded fire flow."
The later photo, taken of the same area more than 80 years later, shows a mass of coniferous green.
"That will burn very differently," Gray said. "That will burn wall-to-wall as a continuous crown fire and a very vigorous surface fire. Fire is a contagion. It acts no different than the COVID virus. It will go wherever there's a susceptible host."
What we should do, he said, is "inoculate the landscape against that kind of spread behaviour."
He said those "carpets of green" are the perfect hosts for large "mega-fires" that are becoming more common, larger, hotter, and harder to fight because of increased temperatures and drought, more extreme wind events, longer fire seasons, and more persistent high pressure weather systems.
Gray is an internationally recognized wildfire ecologist with 40 years of experience in Canada and the U.S. He is the president of R.W. Gray Consulting Ltd. in Chilliwack. His talk in Taghum was organized by the West Kootenay Watershed Collaborative.
He focused on how wildfires affect watersheds, but he also discussed trends in weather and drought that are making wildfires more dangerous. And he discussed policy changes that are needed to protect watersheds and forests from a wildfire future he says is more ominous than governments and industry seem to believe.
The 1938 forest landscape in the photo contained a number of what Gray called "fences," or barriers that slow the progress of a fire.
"The fire is going to hit something. And when it hits something, it has to flank its way around, and in the process, it reduces intensity and severity. It buys time for the weather to change. It buys time for suppression to get there."
Fences on a forest landscape can include recent wildfires, hardwood forests (deciduous forests such as aspen that are less flammable than conifers), re-burns (areas that burned once and then burned again), timber harvests that have then been slash-burned, and other intentional burns. The landscape needs this kind of mix, Gray said.
He explained that he has worked with Indigenous people who have "an extremely sophisticated understanding of fire. I've worked with tribes from Arizona through B.C., and they knew when to burn, how to burn, how often to burn, where to burn, sometimes for individual plant species, but fire was how they survived on this landscape."
Gray said he is currently working with the Ktunaxa Nation on a fire risk and impact assessment across its entire territory.
Watersheds and wildfire
Much of Gray's talk focused on watersheds and water supply.
He said the well-known short-term effects of wildfires on water include severe floods, excessive erosion, and decreased water quality due to increased sediments.
But he also discussed some longer-term effects that are just starting to be noticed. To illustrate this, he showed a photo of an old car, rusted out and abandoned in the woods. He said that car was analyzed to show that it contains a number of toxins including chromium, lead, copper, Iron and zinc, all of which could be reintroduced to the soil and groundwater by a fire.
"So if you're in an area where there was industrial activity such as mining, historically, all of those emissions are in the soils. They haven't gone away. They bio-accumulated in some places, but once you have a fire, it basically remobilizes those."
He added that the McDougall Creek wildfire in West Kelowna in 2023 burned more than 200 structures plus cars, boats, RVs and industrial sites, all made of many toxic substances that will all make their way to Okanagan Lake.
With larger, more numerous, and hotter fires, Gray said, we will see water supply issues because of changes in the timing and flow of water from the mountain snowpacks, including increased peak flows in the spring and decreased late summer flows, with both becoming less predictable.
Gray said a high-severity fire affects not only vegetation and water but soils.
"Fires smouldering at high temperatures, it kills soil biota, it volatilizes nutrients, it changes soil structure."
Some of these so-called "zombie fires" smoulder underground for months or all winter, he said.
"You're not going to get plant growth back there very quickly, because it's hard to grow in sterilized soil. In addition to that, the tree roots have decayed and there's nothing to hold the soil in place."
Policy and political will
Gray said it has been shown that clearcuts should be slash-burned before they are replanted, to get rid of downed branches and small trees that supply fuel to the next wildfire. But this is not current practice.
He said he and other ecologists are trying to convince industry to return to post-harvest slash burning but with higher utilization of the wood, so that all they are burning is the branches and other fine debris.
And they are trying to convince them of the need for a different kind of landscape, one with fences against fires.
The problem, Gray said, is not lack of solid ecological information but of leadership.
"Right now, there doesn't seem to be a lot of that. We should be in crisis mode."
He said the forest industry is aware of the need for change but the government needs to take the uncertainty out of it and provide incentives to the industry.
Governments and business, Gray said, have a habit of focusing on an issue and then bringing in fire as a side-issue that also needs to be addressed. But fire has become the main issue.
"This is probably going to come across a really quite cavalier, but fire is driving the bus. Everything else is going to take a backseat to it ... Fire cleans the plate. We have to create conditions so that fire still provides for biodiversity and clean water and is not a threat to our communities and old growth."
