The San Francisco Peaks rise to an elevation of 12,633 feet. While leading a scientific expedition to the Peaks in 1889, Mr. C. Hart Merriam developed the concept of life zones, which describe how plant and animal community distribution is affected by elevation, temperature, and exposure. The area is within the transition zone, dominated by ponderosa pine forest. Climbing the Peaks reveals ponderosa giving way to aspen, fir, spruce, bristlecone pine, and ultimately alpine tundra at the summit.