Cloud forests are unique ecosystems that occur only in specific tropical mountain areas. The distinctive weather conditions make them suitable for thousands of plants and animals that can be found nowhere else on Earth.

Clouds and precipitation
A tropical cloud forest is a specific type of rainforest that occurs at relatively high elevations. The most clearly identifiable characteristic of a cloud forest isclouds! Low cloudbanks form over the mountains such that the forest is actually immersed in clouds much of the time. When this happens, the relative humidity is 100%, making cloud forests exceedingly wet places. Large amounts of water are deposited directly onto vegetation from clouds and light mist; the highest elevations of the forest are almost always dripping water from the leaves. This constant supply of above-ground water makes a cloud forest excellent habitat for epiphytes (plants that grow on other plants). In the area surrounding Monteverde, Costa Rica, there are at least 878 species of epiphytes, including 450 orchids. To a visitor accustomed to drier temperate forests, the abundance of epiphytes is the most striking difference. Tree trunks are almost always covered with mosses, bromeliads, ferns, and other plants. Visitors are seldom able to view the whole forest because of the clouds and mists constantly drifting in and out amongst the trees.

Elevation
In Monteverde, the cloud forest spans the Continental Divide, extending from about 1500m (4920ft) on the Pacific slope and 1350m (4430ft) on the Atlantic slope up to the highest peaks of the Tilaran Mountains at around 1850m (6070ft). Lower, more protected areas may have a forest canopy 30-40m (115ft) high, while the upper elevations of the forest are so windswept that the trees are stunted to no more than 5-10m (16-33ft). This is referred to as elfin forest, and was the home of the now-extinct Golden Toad (Bufo periglenes).

Temperature
Although Monteverde is only 10oN of the Equator, temperatures are rather cool because of the elevation. The average annual temperature is about 18.5oC (65oF), which varies only by a few degrees through the changing seasons. It is possible for temperatures to fall below 10oC (50oF); visitors often find that the shorts and T-shirt they wore in the lowlands aren't enough here.

Source: Kenneth L. Clark, Roberts O. Lawton, and Paul. R. Butler - The Physical Environment; William A. Haber - Plants and Vegetation. In Nalini M. Nadkarni and Nathaniel T. Wheelwright (eds). 2000. Monteverde: Ecology and Conservation of a Cloud Forest. Available now from Oxford University Press.