Fire suppression has dramatically altered the natural regimes that I just described. A few snapshots from across the country:
Aspen forests are static or in decline throughout the Rockies.
The hardy, beautiful aspen is quick to regenerate in areas visited by fire. Aspen, in fact, all but depend upon fire to create new stands, as they rarely reproduce by seed. When a mature tree is burned off aboveground, its roots survive and immediately send up a dense array of saplings. Following even the largest fires, a new aspen stand can reappear in ten years. A large percentage of the mature aspen parks in Jackson Hole, Wyoming, are the offspring of catastrophic fires that swept the region between 1850 and 1890. Core samples of old aspen stands in Yellowstone National Park showed that these forests, too, appeared in the wake of severe fires during the same period.
Today, with fire suppression, there are few young forests of aspen across the Rocky Mountain region. In Wyoming, biologists rank aspen parklands second only to wetlands for overall importance to wildlife.
Across California and southern Oregon, the California black oak woodlands are disappearing.
The black oak can't take much fire; mature trees often die following even a moderate ground fire. But the tree recovers quickly, sprouting from both its root system and root crown. Undamaged trees sow a profusion of acorns into the cleaned, burned ground. Throughout its range, fire suppression has allowed more shade-tolerant conifers like Douglas-fir to move in. The airy, parklike oak woodlands become loaded with young conifers and deadfall. When fire appears, it finds plenty of fuel. Burning bigger, hotter, and longer, black oaks suffer a severe setback.
Even if the forest fails to burn, the unnatural amounts of shade and litter on the ground create poor conditions for acorn survival. On the Shasta-Trinity National Forest in California, a prescribed burn allowed surviving black oaks to produce a bumper crop of acorns with a high rate of survival. On nearby, unburned ground, the acorn crop failed due to predation by insects living on the forest floor.
Details mentioned in this article were accurate at the time of publication