UBC Reports | Vol. 50 | No. 6 |
Jun. 3, 2004
Fighting Fire with Fire
Controlled burns bring back native plants
By Michelle Cook
As British Columbians brace for another summer of high forest
fire risk, UBC researcher Andrew MacDougall is preparing to
deliberately set alight some patches of the Cowichan Garry
Oak Preserve south of Duncan to study fire's power to restore
This summer will mark the fifth year that MacDougall has
conducted controlled burn experiments in the preserve to examine
whether low-intensity fires will help native plants regenerate
in the rare ecosystem. The goals of the project are to better
understand the causes and consequences of plant invasion on
native species, as well as examine possible strategies for
managing the ecosystem through the re-introduction of controlled
burning that had traditionally been done by First Nations
"The area is a hot spot for biodiversity in Canada,"
says MacDougall, who recently completed a PhD thesis on his
work in the Garry oak preserve under the supervision of botany
professor Roy Turkington. "It hasn't seen fire in more
than 150 years, and invasive grasses and other introduced
species have come in and choked out the native plants. They
also generate large amounts of highly combustible plant litter,
increasing the risk of forest fire."
In Canada, Garry oak ecosystems are found only on Vancouver
Island, the nearby Gulf Islands and in the Fraser Valley.
They support 91 species that have been designated at risk
in B.C. or nationally.
The 18-hectare Cowichan preserve, owned by the Nature Conservancy
of Canada, is the most intact remaining example of the ecosystem
in the country. It is home to five endangered or threatened
species: the yellow prairie violet, white-top aster, Howell's
tritelaia, the Propertius dusky wing butterfly and the barn
Historical records, researched by MacDougall and colleagues
at the University of Victoria, show that prior to European
settlement, First Nations people in the area used planned
burns to manage the land and cultivate a supply of indigenous
camas bulbs. Camas, a lily plant that produces a potato-like
tuber, was an important food source for many Coastal tribes.
The under-burning also encouraged the growth of native grasses,
presumably to attract deer and elk to the area to graze.
The one-square-metre patches of ground that MacDougall burned
in past years have begun to produce results.
Earlier this spring, colourful purple-flowered camas plants
and native prairie violets were thriving in meadows amid the
stately oaks. MacDougall says it has been interesting to watch
the ecosystem respond to fire management techniques.
"We've noticed significant increases in the growth and
reproduction of many native plants. Prairie violet has tripled
in cover," MacDougall says. "The other good news
is we've gotten rid of the invasive grasses. We'll never have
the fuel loads that we did before we began the burning experiments."
He says the experiment also produced some unexpected results.
"At first glance, the high abundance of invasive plants
suggests that they drive biodiversity decline," MacDougall
says. "However, our research has also revealed a hidden
but significant impact of habitat fragmentation on the ability
of native species to re-colonize invaded areas. Because exotics
[introduced species] thrive in our highly developed, contemporary
landscapes, they can dominate by default rather than by competition
even though their dominance suggests otherwise."
Tim Ennis, the Nature Conservancy's director of land stewardship
for the B.C. region, says the UBC research will not only help
people doing conservation in other parts of Canada, it will
help the Conservancy to make management decisions for the
Maple Bay property.
"When dealing with the invasive species, they are difficult
to control because they grow in among the native plants,"
Ennis says. "We needed to find more efficient strategies
for management, and Andrew's results have given us the tools
we need to handle them. We're taking the same treatments he
has succeeded with and are applying them on a larger area."
The Nature Conservancy is currently using a combination
of controlled burning, mowing and seeding to transform the
Garry oak landscape in the years to come.
"Rather than a carpet of exotic grasses punctuated by
one wildflower, what we want to achieve is a carpet of native
wildflowers," Ennis says.
MacDougall says it remains to be seen whether some of the
rarer native plants will be able to make a comeback, and the
study is expected to continue for at least another five years.
But the initial results have proven that larger scale, rotational
controlled burns are a conservation option that could also
help to lower the risk of forest fires.
"Invasive [introduced] grasses are fuel for fires and
we need to get a handle on these fuel loads. Low intensity
fires can greatly reduce the hazard of larger, destructive
wildfires. Controlled burning would have the benefit of protecting
an area from damage in the event of a forest fire," MacDougall
As for the oaks themselves, MacDougall says they love fire.
"Unless they are very small, it doesn't harm them."