Cloud forest

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Tree ferns in a cloud forest on Mount Kinabalu, Borneo Cloud forest mount kinabalu.jpg
Tree ferns in a cloud forest on Mount Kinabalu, Borneo

A cloud forest, also called a water forest and primas forest, is a generally tropical or subtropical, evergreen, montane, moist forest characterized by a persistent, frequent or seasonal low-level cloud cover, usually at the canopy level, formally described in the International Cloud Atlas (2017) as silvagenitus. [1] Cloud forests often exhibit an abundance of mosses covering the ground and vegetation, in which case they are also referred to as mossy forests. Mossy forests usually develop on the saddles of mountains, where moisture introduced by settling clouds is more effectively retained. [2]

Tropical and subtropical moist broadleaf forests biome

Tropical and subtropical moist broadleaf forests (TSMF), also known as tropical moist forests, are a tropical and subtropical forest habitat type defined by the World Wide Fund for Nature. The habitat type is sometimes known as jungle.

Cloud visible mass of liquid droplets or frozen crystals suspended in the atmosphere

In meteorology, a cloud is an aerosol consisting of a visible mass of minute liquid droplets, frozen crystals, or other particles suspended in the atmosphere of a planetary body or similar space. Water or various other chemicals may compose the droplets and crystals. On Earth, clouds are formed as a result of saturation of the air when it is cooled to its dew point, or when it gains sufficient moisture from an adjacent source to raise the dew point to the ambient temperature. They are seen in the Earth's homosphere. Nephology is the science of clouds, which is undertaken in the cloud physics branch of meteorology.

<i>International Cloud Atlas</i> cloud atlas

International Cloud Atlas is a cloud atlas that was first published in 1896 and has remained in print since then. Its initial purposes included aiding the training of meteorologists and promoting more consistent use of vocabulary describing clouds, which were both important for early weather forecasting. The first edition featured color plates of color photographs, then still a very new technology, but noted for being expensive. Numerous later editions have been published.


Distribution and climate

One of the hanging bridges of the Sky walk at the Monteverde Cloud Forest Reserve in Monteverde, Costa Rica disappearing into the clouds Costa rica santa elena skywalk.jpg
One of the hanging bridges of the Sky walk at the Monteverde Cloud Forest Reserve in Monteverde, Costa Rica disappearing into the clouds

Dependent on local climate, which is affected by the distance to the sea, the exposition and the latitude (from 23°N to 25°S), the altitude varies from 500 m to 4000 m above sea level. Typically, there is a relatively small band of altitude in which the atmospheric environment is suitable for cloud forest development. This is characterized by persistent fog at the vegetation level, resulting in the reduction of direct sunlight and thus of evapotranspiration. [3] [4] Within cloud forests, much of the moisture available to plants arrives in the form of fog drip, where fog condenses on tree leaves and then drips onto the ground below.


Evapotranspiration (ET) is the sum of evaporation and plant transpiration from the Earth's land and ocean surface to the atmosphere. Evaporation accounts for the movement of water to the air from sources such as the soil, canopy interception, and waterbodies. Transpiration accounts for the movement of water within a plant and the subsequent loss of water as vapor through stomata in its leaves. Evapotranspiration is an important part of the water cycle. An element that contributes to evapotranspiration can be called an evapotranspirator.

Fog drip is water dripping to the ground during fog. It occurs when water droplets from the fog adhere to the needles or leaves of trees or other objects, coalesce into larger drops and then drop to the ground.

Condensation change of the physical state of matter from gas phase into liquid phase; reverse of evaporation

Condensation is the change of the physical state of matter from the gas phase into the liquid phase, and is the reverse of vaporisation. The word most often refers to the water cycle. It can also be defined as the change in the state of water vapour to liquid water when in contact with a liquid or solid surface or cloud condensation nuclei within the atmosphere. When the transition happens from the gaseous phase into the solid phase directly, the change is called deposition.

Annual rainfall can range from 500 to 10,000 mm/year and mean temperature between 8 and 20 °C. [3] [4]

While cloud forest today is the most widely used term, in some regions, these ecosystems or special types of cloud forests are called mossy forest, elfin forest, montane thicket, and dwarf cloud forest. [4]

The definition of cloud forest can be ambiguous, with many countries not using the term (preferring such terms as Afromontane forest and upper montane rain forest, montane laurel forest, or more localised terms such as the Bolivian yungas , and the laurisilva of the Atlantic Islands), [5] [6] and occasionally subtropical and even temperate forests in which similar meteorological conditions occur are considered to be cloud forests.

Afromontane concept

The Afromontane regions are subregions of the Afrotropical realm, one of the Earth's eight biogeographic realms, covering the plant and animal species found in the mountains of Africa and the southern Arabian Peninsula. The Afromontane regions of Africa are discontinuous, separated from each other by lower-lying areas, and are sometimes referred to as the Afromontane archipelago, as their distribution is analogous to a series of sky islands.

Laurel forest Type of subtropical forest

Laurel forest, also called laurisilva or laurissilva, is a type of subtropical forest found in areas with high humidity and relatively stable, mild temperatures. The forest is characterized by broadleaf tree species with evergreen, glossy and elongated leaves, known as "laurophyll" or "lauroid". Plants from the laurel family (Lauraceae) may or may not be present, depending on the location.

Yungas Natural region

The Yungas is a narrow band of forest along the eastern slope of the Andes Mountains from Peru, Bolivia, and northern Argentina. It is a transitional zone between the Andean highlands and the eastern forests. Like the surrounding areas, the Yungas belong to the Neotropic ecozone; the climate is rainy, humid, and warm.

Only 1% of the global woodland consists of cloud forests. [3]

Important areas of cloud forest are in Central and South America, East and Central Africa, Indonesia, Malaysia, the Philippines, Papua-New Guinea, and in the Caribbean. [7]


Hanging moss in a cool temperate rainforest at Budawang National Park, Australia Papillaria Cloudforest-Mt Budawang.jpg
Hanging moss in a cool temperate rainforest at Budawang National Park, Australia

In comparison with lower tropical moist forests, cloud forests show a reduced tree stature combined with increased stem density and generally the lower diversity of woody plants. [3] [4] Trees in these regions are generally shorter and more heavily stemmed than in lower-altitude forests in the same regions, often with gnarled trunks and branches, forming dense, compact crowns. Their leaves become smaller, thicker and harder with increasing altitude. [8] The high moisture promotes the development of a high biomass and biodiversity of epiphyte, particularly bryophytes, lichens, ferns (including filmy ferns), bromeliads and orchids. [3] [4] The number of endemic plants can be very high. [3]

An important feature of cloud forests is the tree crowns can intercept the wind-driven cloud moisture, part of which drips to the ground. This fog drip occurs when water droplets from the fog adhere to the needles or leaves of trees or other objects, coalesce into larger drops and then drop to the ground. [9] It can be an important contribution to the hydrologic cycle. [4]

Due to the high water content of the soil, the reduced solar radiation and the low rates of decomposition and mineralization, the soil acidity is very high, [4] [10] [11] with more humus and peat often forming the upper soil layer. [4]

Stadtmüller (1987) distinguishes two general types of tropical montane cloud forests:

Temperate cloud forests

Although far from being universally accepted as true cloud forests, several forests in temperate regions have strong similarities with tropical cloud forests. The term is further confused by occasional reference to cloud forests in tropical countries as "temperate" due to the cooler climate associated with these misty forests.

Temperate cloud forest on La Palma, Canary Islands Forest Los Tilos.jpg
Temperate cloud forest on La Palma, Canary Islands

Distribution of temperate cloud forests


At the edge of the Panamanian side of the Parque Internacional la Amistad DirkvdM cloudforest.jpg
At the edge of the Panamanian side of the Parque Internacional la Amistad

Current situation

Seaborne moisture is vital to the cloud forest of Fray Jorge that is surrounded by the arid southern reaches of the Atacama Desert. Nimbosilva de Fray Jorge.jpg
Seaborne moisture is vital to the cloud forest of Fray Jorge that is surrounded by the arid southern reaches of the Atacama Desert.

In 1970, the original extent of cloud forests on the Earth was around 50 million hectares. Population growth, poverty and uncontrolled land use have contributed to the loss of cloud forests. The 1990 Global Forest Survey found that 1.1% of tropical mountain and highland forests were lost each year, which was higher than in any other tropical forests. [13] In Colombia, one of the countries with the largest area of cloud forests, only 10–20% of the initial cloud forest cover remains. [3] Significant areas have been converted to plantations, or for use in agriculture and pasture. Significant crops in montane forest zones include tea and coffee, and the logging of unique species causes changes to the forest structure. [4]

In 2004, an estimated one-third of all cloud forests on the planet were protected at that time. [14]

Impact of climate change

Because of their delicate dependency on local climates, cloud forests will be strongly affected by global climate change. Results show that the extent of environmentally suitable areas for cloud forest in Mexico will sharply decline in the next 70 years. [15] A number of climate models suggest low-altitude cloudiness will be reduced, which means the optimum climate for many cloud forest habitats will increase in altitude. [16] [17] Linked to the reduction of cloud moisture immersion and increasing temperature, the hydrological cycle will change, so the system will dry out. [17] This would lead to the wilting and the death of epiphytes, which rely on high humidity. [16] Frogs and lizards are expected to suffer from increased drought. [17] Calculations suggest the loss of cloud forest in Mexico would lead to extinction of up to 37 vertebrates specific to that region. [18] In addition, climate changes can result in a higher number of hurricanes, which may increase damage to tropical montane cloud forests. All in all, the results of climate change will be a loss in biodiversity, altitude shifts in species ranges and community reshuffling, and, in some areas, complete loss of cloud forests. [16]

In botanical gardens

Cloud-forest conditions are hard and expensive to replicate in a glasshouse because it is necessary to maintain a very high humidity. This is usually expensive as a high temperature must usually be maintained as well, and a high temperature combined with high humidity calls for good air circulation or else fungi and algae will develop. Such displays usually are quite small, but there are some notable exceptions. For many years, the Singapore Botanic Gardens have a so-called coolhouse, whereas the Gardens by the Bay features a 0.8 hectares (2.0 acres) coolhouse that is simply named "Cloud Forest". The latter features a 35-metre (115 ft)-high artificial mountain clad in epiphytes such as orchids, ferns, clubmosses, bromeliads and others. [19]


  1. Sutherland, Scott (March 23, 2017). "Cloud Atlas leaps into 21st century with 12 new cloud types". The Weather Network. Pelmorex Media. Retrieved 24 March 2017.
  2. Clarke 1997, p. 29.
  3. 1 2 3 4 5 6 7 Häger 2006, p. [ page needed ].
  4. 1 2 3 4 5 6 7 8 9 10 Hamilton, Juvik & Scatena 1995.
  5. García-Santos, Bruijnzeel & Dolman 2009.
  6. 1 2 3 García-Santos 2007, p. [ page needed ].
  7. "Resources Data - UNEP-WCMC".
  8. Bruijnzeel & Proctor 1995 quote from Hamilton, Juvik & Scatena 1995
  9. "Fog drip - AMS Glossary". American Meteorological Society . Retrieved 2014-12-15.
  10. van Steenis 1972, p. [ page needed ].
  11. Grubb & Tanner 1976.
  12. Vogelmann 1973 and Bruijnzeel 1990 , p. [ page needed ] quote by Hamilton, Juvik & Scatena 1995
  13. 1 2 3 4 Bruijnzeel & Hamilton 2000, p. [ page needed ].
  14. Kappelle 2004 quote by Häger 2006 , p. [ page needed ]
  15. Ponce-Reyes et al. 2013.
  16. 1 2 3 Foster 2001.
  17. 1 2 3 Bubb et al. 2004, p. [ page needed ].
  18. Ponce-Reyes et al. 2012.
  19. "Cloud Forest Facts and Figures".

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