Cloud forest

in Monteverde, Costa Rica disappearing into the clouds Cloud forest distribution is governed by the mixing of latitude, proximity to the ocean, topography, and elevation. Most tropical cloud forests occur between latitudes 25°N and 25°S and at elevations ranging from approximately 500 m to 4,000 m above sea level. Within this broad range, suitable conditions are typically restricted to a relatively narrow altitudinal band where atmospheric temperature and humidity permit persistent cloud formation at vegetation level. The defining climatic mechanism is orographic lift: prevailing winds carry moisture-laden air from the ocean toward mountain ranges, and as the air is forced upward it cools at the dry adiabatic lapse rate until it reaches the dew point, at which point water vapor condenses into cloud. The elevation at which this condensation occurs, the cloud base, is where cloud forests characteristically develop. Once cloud envelops the canopy, direct sunlight is reduced, lowering evapotranspiration and creating the persistently humid conditions in which cloud forest vegetation thrives. == Characteristics ==

, Philippines , Australia Compared with lower-altitude tropical moist forests, cloud forests are characterised by reduced tree stature combined with increased stem density and, generally, lower woody plant diversity. The persistently high moisture promotes exceptional development of epiphytes, plants that grow on other plants without making them parasites, particularly bryophytes (mosses and liverworts), lichens, ferns (including filmy ferns), bromeliads, and orchids. Epiphyte biomass can be very high; in some cloud forests, the weight of mosses and other epiphytes on a single tree exceeds the weight of the tree's own foliage. The number of endemic plant species can also be very high. Stadtmüller (1987) distinguishes two general types of tropical montane cloud forests: Areas with high annual precipitation due to frequent cloud cover combined with heavy and sometimes persistent orographic rainfall. These forests have perceptible canopy strata, a high number of epiphytes, and a thick peat layer with high water-storage capacity. Drier areas with mainly seasonal rainfall, where cloud stripping, the interception and deposition of cloud moisture by vegetation, accounts for a large proportion of the total moisture available to plants. ==Distribution of tropical montane cloud forests==

File:Distribution of tropical cloud forests.png|thumb|Distribution of tropical montane cloud forests in 2016 Important areas occur in Central and South America (principally Costa Rica, Venezuela, Honduras, El Salvador, Guatemala, Mexico, Ecuador, and Colombia), East and Central Africa, India, Sri Lanka, Thailand, Vietnam, Indonesia, Malaysia, the Philippines, Hawaii, Papua New Guinea, and the Caribbean. == Conservation status ==

Cloud forests occupied 0.4% of the global land surface in 2001 and harbored ~3,700 species of birds, mammals, reptiles, amphibians, and tree ferns (~15% of the global diversity of those groups), with half of those species entirely restricted to cloud forests. == Temperate cloud forests ==

Although not universally accepted as true cloud forests, several forests in temperate regions share strong structural and climatic similarities with their tropical counterparts. The classification is further complicated by the occasional use of "temperate" to describe cool-climate cloud forests within tropical countries. , Canary Islands Temperate cloud forest distribution by country: • Argentina – Salta, Jujuy, Catamarca and Tucumán (Southern Andean Yungas) • Australia – Lamington National Park, Springbrook National Park, Mount Bartle Frere and Mount Bellenden Ker (Queensland) and Mount Gower (Lord Howe Island) • Brazil – Serra do Mar coastal forests • Chile – Bosque de Fray Jorge National Park • China – Yunnan Plateau, mountains of southern and eastern China • Costa Rica – Monteverde Cloud Forest Reserve. Approximately 10,500 hectares, containing around 2,500 plant species (including the greatest concentration of orchid species of any single site on Earth), 100 species of mammals, 400 species of birds, 120 species of reptiles, and thousands of insect species. • Ethiopia – Harenna Forest, Bale Mountains National Park and Kafa Biosphere Reserve • Fiji Islands – Tropical montane cloud forests of Taveuni and Gau Island • Iran – Eastern Alborz mountains, Golestan Province • Japan – Parts of Yakushima Island • Peru – Bosques Nublados de Udima Wildlife Refuge • Portugal – Azores and Madeira (referring primarily to the wetter, higher-altitude laurisilva) • Sri Lanka – Upper slopes of the Knuckles Mountain Range, Matale • Taiwan – Yuanyang Lake Nature Reserve, Chatianshan Nature Reserve, and Fuxing District, Taoyuan == Conservation status ==

Cloud forests occupied approximately 0.4% of the global land surface in 2001 and harboured around 3,700 species of birds, mammals, reptiles, amphibians, and tree ferns — approximately 15% of global diversity in those groups — with roughly half of those species entirely restricted to cloud forests. Population growth, poverty, and uncontrolled land use have contributed to substantial losses since then. The 1990 Global Forest Survey found that 1.1% of tropical mountain and highland forests were being lost annually — a higher rate than in any other tropical forest type. In Colombia, one of the countries with the greatest cloud forest area, only 10–20% of the original cover is estimated to remain.[7] Significant areas have been converted to plantations, agriculture, and pasture; important crops in montane forest zones include tea and coffee, and selective logging of unique tree species alters forest structure even where outright clearance has not occurred. Conservation efforts in some regions have achieved measurable successes: for example, the Monteverde Cloud Forest Reserve in Costa Rica has maintained and expanded its protected area since its establishment, and similar private and community-led reserves across the Andes have helped stabilize cover in targeted localities. == Importance ==

that is surrounded by the arid southern reaches of the Atacama Desert. == Watershed function ==

Cloud forests play a disproportionately important role in the regional hydrological cycle relative to their small global extent. The cloud-stripping mechanism — whereby tree canopies intercept wind-driven cloud moisture — can effectively double rainfall inputs during dry seasons and add approximately 10% to wet-season totals. This function makes cloud forests critical catchment areas for rivers and groundwater systems serving large human populations, particularly in seasonally dry regions such as coastal Peru and northern Chile where cloud forests are virtually the sole source of freshwater. == Vegetation ==

Tropical montane cloud forests are not as species-rich as tropical lowland forests in terms of overall woody plant diversity, but they provide habitat for many species found nowhere else on Earth. == Fauna ==

Faunal endemism in cloud forests is exceptionally high. In Peru alone, more than one-third of the country's 270 endemic birds, mammals, and frogs are found in cloud forests. Among mammals, the spectacled bear (Tremarctos ornatus), the only bear native to South America, is one of the best-known cloud forest species and serves as an important seed disperser across Andean cloud forests. Amphibian diversity is also notable: the cool, moist microclimate supports many frog and salamander species that are highly sensitive to desiccation and temperature change, making them among the most vulnerable groups to projected climate warming. == Impact of climate change ==

Because cloud forests are defined by a delicate dependency on specific atmospheric conditions at specific elevations, they are among the ecosystems most sensitive to global climate change. As temperatures rise, the elevation at which cloud condensation occurs shifts upward, pushing the cloud base — and therefore the zone suitable for cloud forest — to higher altitudes and reducing the total land area available. A number of climate models indicate that low-altitude cloudiness will be reduced, meaning that some existing cloud forests will experience a drying trend even before temperature-driven habitat loss becomes acute. Taken together, the consequences of climate change for cloud forests include biodiversity loss, disrupted biogeochemistry, altitude shifts in species ranges, wholesale community reshuffling, and, in some areas, complete disappearance of the ecosystem. == Footnotes ==