section_path: Ecology and climate
section_name: Ecology and climate
paragraph_text: Ecology and climate
  
  There are a wide range of environmental factors in the Rocky Mountains. The Rockies range in latitude between the Liard River in British Columbia (at 59° N) and the Rio Grande in New Mexico (at 35° N). Prairie occurs at or below 550 metres (1,800 ft), while the highest peak in the range is Mount Elbert at 4,400 metres (14,440 ft). Precipitation ranges from 250 millimetres (10 in) per year in the southern valleys to 1,500 millimetres (60 in) per year locally in the northern peaks. Average January temperatures can range from −7 °C (20 °F) in Prince George, British Columbia, to 6 °C (43 °F) in Trinidad, Colorado. Therefore, there is no single monolithic ecosystem for the entire Rocky Mountain Range.
  
  Instead, ecologists divide the Rockies into a number of biotic zones. Each zone is defined by whether it can support trees and the presence of one or more indicator species. Two zones that do not support trees are the Plains and the Alpine tundra. The Great Plains lie to the east of the Rockies and is characterized by prairie grasses (below roughly 550 m or 1,800 ft). Alpine tundra occurs in regions above the tree-line for the Rocky Mountains, which varies from 3,700 m (12,000 ft) in New Mexico to 760 m (2,500 ft) at the northern end of the Rockies (near the Yukon).
  
  The U.S. Geological Survey defines ten forested zones in the Rockies. Zones in more southern, warmer, or drier areas are defined by the presence of pinyon pines / junipers, ponderosa pines, or oaks mixed with pines. In more northern, colder, or wetter areas, zones are defined by Douglas firs, Cascadian species (such as western hemlock), lodgepole pines / quaking aspens, or firs mixed with spruce. Near tree-line, zones can consist of white pines (such as whitebark pine or bristlecone pine); or a mixture of white pine, fir, and spruce that appear as shrub-like krummholz. Finally, rivers and canyons can create a unique forest zone in more arid parts of the mountain range.
  
  The Rocky Mountains are an important habitat for a great deal of well-known wildlife, such as wolves, elk, moose, mule and white-tailed deer, pronghorn, mountain goats, bighorn sheep, badgers, black bears, grizzly bears, coyotes, lynxes, cougars, and wolverines. North America's largest herds of elk are in the Alberta–British Columbia foothills forests.
  
  The status of most species in the Rocky Mountains is unknown, due to incomplete information. European-American settlement of the mountains has adversely impacted native species. Examples of some species that have declined include western toads, greenback cutthroat trout, white sturgeon, white-tailed ptarmigan, trumpeter swan, and bighorn sheep. In the U.S. portion of the mountain range, apex predators such as grizzly bears and wolf packs had been extirpated from their original ranges, but have partially recovered due to conservation measures and reintroduction. Other recovering species include the bald eagle and the peregrine falcon.