Past climate change and wildfires. There’s definitely a connection.
Patrick Bartlein, a climatologist from Oregon University, has co-authored a study
relating the effects of Climate change over the past 3,000 years on wildfires in the western
United States. Using cores of sediments extracted from the bottom of mountain lakes, the
researchers have overlaid the data with a record of past climate changes. The sediments
contain layers of charcoal which can be attributed to large fire activity in the area. This allows
the activity to be dated fairly accurately.
There was a time frame between 950 A.D. To 1250 A.D. which is called the ‘Medieval
Climate Anomaly.’ This era was recorded to be unusually warm and dry. According to
Bartlein’s teams data, this coincided with an increase in fires. From the other end of the
spectrum, the centuries from 1400 A.D. to 1700 A.D. have been labeled the ‘Little Ice Age.’
This was a time of cool and moist air moving globally. The fire activity was significantly
reduced during that time. These are just a few examples of events that have led the
climatologists to describe almost 3,000 years of these types of relations.
Given the climate information of the past century and a half, the amount of natural fire
predicted is significantly higher than the amount recorded. The author’s note that this
information only covers the wildfire activity in limited areas in the western United States,
however, global information can be extrapolated. Bartlein states that “If you just look at what
the current climate is like, the rate of biomass burning should be much higher than what
we’ve observed over the 20th century…” The west has been warming since the early 1900’s.
There are a large number of people who consider the start of significant global warming to be
the Industrial Revolution. They attribute the decrease in wildfire to a combination of cattle,
fragmentation of the landscape, and suppression by the population. The cattle graze the
landscape reducing fuel for wildfires. Urban sprawl has broken the west into smaller
contiguous areas, decreasing the risk of fires spreading.
Starting in the 1980’s, the most recent data shows that this ‘fire deficit’ may be
getting ‘paid back.’ “Since the 1980s, fire frequency in the West has increased more than 300
percent, and the annual acreage burned has jumped 500 percent…” says Anthony Westerling
of the University of California’s Sierra Nevada Research Institute. These authors all recognize
that these studies don’t get into the specifics of types of ecosystems, acknowledging that there
could be significant differences between, for instance, grass lands and forests. This is more of
a ‘broad stroke picture’ of events.
While the factors reducing wildfire vulnerability continue to grow, the connection
between fires and climate still exist and we must stay ever vigilant to manage our western
landscape. The problem extends beyond our own lands and is, in fact, worse in other parts of
the world. While natural wildfire is an extremely difficult disaster that is near impossible to
control, ‘an ounce of prevention goes a long way’ as the old saying goes.
– Bj Hile
Tom Yulsman. ‘Fire Deficit May Trigger Fiercer Wildfires’ June 29th , 2012
Scientific American <http://www.scientificamerican.com/article.cfm?id=fire-deficit-trigger-
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