Yellowstone Fire Grows, Park Remains Open

Naturally occuring forest fires are part of the ecological system that sustains and replenishes wilderness.

In 1988 Yellowstone had the worse forest fire in recent history. It was the driest year, with only 32% of the normal precipitation falling. In fact, the region started drying out as early as the fall of 1987 when the expected autumn rains failed to manifest themselves. A record low snow pack and early spring run-off followed the winter. By June of 1988, the Palmer Drought Index, which measures precipitation, soil moisture, and evaporation, indicated extreme drought conditions in Yellowstone. During the period of 1972 through 1988, 335,833 hectares burned, but an astonishing 95.7% (321,833 hectares) burned during 1988.

Many people thought that Yellowstone would never recover. Scientists, however, knew that fire was a necessary part of the cycle of life in a forest. Life would not only go on, but would also benefit from the fire. The fires left large patches of cleared ground opened to the sun. Seeds released from pinecones took root almost immediately. Lodgepole pine seedlings began to grow at the rate of an inch or two per year. Wildflowers were abundant by the following spring, and the grasses and shrubs were a rich green. Nutrients from the ash caused the vegetation to prosper. Trees that didn't fall became feeding grounds for insects, and the insects in turn attracted many woodpeckers. The holes left by woodpeckers attracted many birds that used them for nests. Yellowstone was far from dead.

The fire had very little negative effects on the animals. There were 396 large animal deaths from the fire, most by smoke inhalation, including 9 bison, 6 black bears, and 333 elk. Thousands of elk perished during the following winter because of a lack of food, but the elk population rebounded to pre-fire numbers by 1993. 

The fire had many short-term consequences on terrestrial ecosystems including a greater availability of nutrients from ash, widespread soil modification, and changes in water chemistry in rivers and streams. Increases in suspended-sediment loads in streams resulted in a greater fish mortality rate, but scientists studying this phenomenon expected the concentrations of suspended-sediment in streams to decline as terrestrial vegetation recovered and as soils stabilized.

There does seem to be one casualty of the fire. The aspen are not recovering as expected. Aspen is a minor species in Yellowstone covering only about 2% of the park, but is significant because it is the only deciduous tree found in the forest. Aspen, located primarily in the northern winter range of Yellowstone, support a large number and a wide diversity of birds and animals. Fire destroyed 22% of the northern range, including many of the mature aspen, but new sprouts were produced. These sprouts, however, were fed on by thousands of elk that spend the winter months in the northern winter range. The aspen are not expected to recover to pre-fire levels.

The fires seem frightening to us, and especially if you live in California, but in wilderness forest they are part of the eco system that is in a constant state of decline and renewel.  Some species of pine trees like the Bishop Pine, not native to Yellowstone,  need fire to regenerate and actually decline in areas where fire suppression is practiced. Fire suppression has led to slow population declines over the last century by altering the dynamics of stands in fire-prone regions  In Yellowstone in the absence of fire, whitebark pine in these stands is replaced by more shade-tolerant, fire-intolerant species such as the subalpine and Engelmann spruce.