It is rather amazing how often well-intentioned human activities have unintended (and often disastrous) consequences. This “law of unintended consequences” happens in economics, politics and of course ecosystems, generally as the result of applying simple solutions to complex systems.
A good example of this law at work in the environment is our attempts to suppress wildfires. The intended outcome was that with fewer wildfires there would be more timber to harvest, thus more jobs and more revenue for governments. The unintended consequence is that over the past century wildfires have become hotter and larger and have actually probably destroyed more timber than has been saved. Natural fires occurred often enough that fuel loads in the forests never really accumulated substantially, so when fires did occur they burned through an area rapidly and at relatively low temperatures and with flames that seldom reached the crowns of the larger trees, so most of the adult trees survived the fires. With fires being suppressed, when they did occur much more fuel had accumulated so the fires were hotter, the flames higher and the adult trees died.
A recent local example of such a fire was the Okanagan Mountain fire of 2003 started by a lightning strike. The damage from this fire was substantial with homes burned, iconic railroad trestles destroyed and much habitat reduced to ashes.
The fire started in Okanagan Mountain Provincial Park which had been established in 1973. Beginning in 1993, the Central Okanagan Naturalists’ Club assisted by the South Okanagan Naturalists’ Club carried out annual bird and animal surveys so that at the time of the fire we had a decade long pre-fire data base. These bird and critter counts were resumed after the fire so we can get a pretty good idea of some of the changes wrought by the fire. Les Gyug of the Central Okanagan Naturalist’s Club kindly provided me with the data. As one might expect, there were both “winners” and “losers” amongst the species for which there was sufficient data.
There was of course a dramatic change in the habitat; with so many adult trees killed, the crown cover was significantly reduced and thus the amount of sunlight reaching the ground dramatically increased with a corresponding increase in grasses and shrubs. This resulted in a major change in the number of browsing/grazing animals. Mule deer increased from less than 10 per year before the fire to more than 50 afterwards. The number of elk counted doubled from about 125 to around 250. Theoretically this should result in an increase in cougars as there is now more prey for them to eat.
The number of bird species observed increased from an average of 93 per year to 105 per year after the fire, but the number of individual birds actually decreased from an average of 1,938 per year to 1,735 per year. This is a decrease of just over 10 per cent. About 10 per cent of the bird species showed a significant decline in numbers.
The big “winners” amongst the birds were various woodpeckers and the two local species of bluebirds. The woodpeckers increased because of the increase in dead trees with lots of bugs to eat, while the bluebirds increased because they like open to semi-open areas, they eat bugs and they nest in cavities in dead trees.
Unfortunately, many species such as snakes and other reptiles and amphibians are very difficult to accurately count so we don’t know what effect the fire had on these species. It is likely there are many more changes that we’ve failed to document. Since the previous master plan for the park is now more than 20 years old let’s hope a new one will be forthcoming and will recognize the role of fire in healthy ecosystems.
To find out more about the South Okanagan Naturalists’ Club visit our website at: sonc.tripod.com.
Bob Handfield is the past-president of the South Okanagan Naturalists’ Club.