Physical Characteristics
All mountain ecosystems share the property of high altitude, rising rapidly from the surrounding terrain. Generally, mountainous regions are defined as any rugged gradient rising above 5,000 feet. Mountains are distinguished from plateaus by their grade. While plateaus are also found at 5,000 feet or more above sea level, they do not share the steep incline of a mountainous landform. Mountains cover approximately one fifth of the world's surface. Additionally, 80 percent of the world's fresh water originates in the mountains.
Weather and Climate
While the specific weather experienced in a given mountainous region may vary depending on location and altitude, some climate characteristics are shared between regions. First of all, mountains are subject to drastic changes in temperature and weather from moment to moment. A thunderstorm can roll in from a clear sky in minutes, or warm temperatures can plummet below freezing over a very short amount of time. The same massive variations occur from one level of altitude to the next. Mountain ranges are sometimes subject to more precipitation than other ecosystems.
Life and Biodiversity
Mountain ranges are home to some of the greatest regions of biodiversity on the planet. The Sierra Nevada mountain range alone is estimated to house from 10,000 to 15,000 separate species of plants and animals. Part of this biodiversity is a result of rapid changes in climate based on altitude, which results in habitations for many types of organisms. Due to the fragile nature of mountain ecosystems, large numbers of native plants and animals are considered at risk or endangered by organizations worldwide. Mountain ranges also provide homes for approximately ten percent of the world's human population.
Sensitivity
Mountain ecosystems are some of the most sensitive in the world. They are subject to extreme swings in weather, which can prevent recovery of lost biomass. They are vulnerable to a wide range of natural disasters that are not nearly as dangerous in the lowlands. These include avalanches, erosion, lava flows, and earthquakes. Because some of the habitation belts in mountainous regions are very small and easily destroyed, the species housed there can be easily reduced in number. The fragile nature of mountainous ecosystems is a cause for great concern, due to the critical role they play in the life cycle both in the mountains and in the lands below.