Definition of a Cloud Forest
In tropical montane cloud forests (TMCF), clouds cover the vegetation either seasonally or year-round. The cloud cover enables the vegetation to capture needed moisture, a process described as horizontal precipitation. The phenomenon of horizontal precipitation enables the forest to flourish even in the dry season. In TMCFs and surrounding areas, horizontal rain provides up to 50 percent of the water for the hydrologic cycle that humans, animals, and vegetation depend on.
Characteristics of a Cloud Forest
Though TMCFs are located in diverse areas, they share common characteristics. TMCFs are composed of forest ecosystems with a distinct structure that typically occurs within a relatively narrow altitudinal zone. For example, in Ecuador the cloud forest has an altitude range of 1400 to 3500 meters above sea level. Within this zone, the atmospheric environment is characterized by persistent, frequent, or seasonal cloud cover at the vegetation level. Enveloping clouds or wind-driven clouds influence atmospheric interaction by reducing solar radiation and vapor deficit, wetting the canopy, and generally suppressing evapotranspiration.
Though the precipitation in TMCFs varies from 500 to 10,000 millimetres per year, forests can maintain themselves because rainfall is only part of the hydrologic cycle. Net precipitation resulting from rainfall is significantly augmented by direct canopy interception of cloud water, horizontal precipitation or cloud stripping. In addition to deriving moisture through horizontal precipitation, cloud forest vegetation also thrives because it conserves water by consuming it over a long period of time. (Hamilton et al. 1995).
Vegetation of the Cloud Forest
TMCFs are also identified by their high proportion of epiphytes (bromeliads, orchids, lichens, mosses, and filmy ferns) and a corresponding reduction in the number of woody climbers. Endemism and biodiversity in terms of tree species of herbs, shrubs, and epiphytes also can be relatively high considering the comparatively small area in which they grow. For example, TMCFs account for 26 percent of the endemism of Peru and 260 of the world’s nationally endemic species live cloud forest habitats (Hamilton et al. 1995).
One emblematic botanical group of the TMCF is the orchid family. Orchidaceaeis one of the most diverse flowering plant families in the world, but the majority of orchid species grow in the neotropics (Dressler 1981). In fact, Ecuador has the second most diverse orchid population in the world, with the greatest orchid diversity occurring from 300 to 3000 meters above sea level. At present, there are more than 3290 described species and an estimated 462 more in need of identification (Dodson and Escobar 1994). With such a significant percentage of the world’s total orchid diversity (11 to 13 percent), Ecuador has identified TMCFs as areas in need of preservation.
Preserving the Cloud Forest
There are many reasons why it is important to preserve cloud forests:
- Biodiversity: There is substantial evidence that the number of species of epiphytes, shrubs, herbs, and ferns increases with altitude in the humid tropics. Therefore, the diversity of TMCF flora is comparable to that of tropical lowland rain forests, though TMCFs have not received equal public attention (Wuethrich 1993).
- Endemism: TMCFs contain high levels of endemic species. These are species found only in specific ecosystems and do not occur anywhere else in the world.
- Climate change: The special characteristics of the TMCF make many of them excellent sites for monitoring the impact of global climate and air quality change (Hamilton et al. 1997).
- Ecological sensitivity: TMCFs are highly susceptible to disturbance and have a low level of resilience. Once the ecosystem is disturbed, it takes more time for it to be restored to its former state than forests at lower altitudes.
- High deforestation and habitat lost: TMCFs are disappearing at an alarming rate. The annual rate of TMCF loss is 1.1 percent, 0.3 percent higher than the rate of rainforest loss (Hamilton et al. 1997).
- Insufficient research: Not enough research has been conducted to know all of the benefits of TMCFs. However, we do know that TMCFs inhibit erosion and horizontal precipitation is an important part of the hydrological cycle.
Threats to the Cloud Forest
Though we have identified the importance of tropical montane cloud forests, they are threatened throughout the world. Some of these threats include:
- Expansion of subsistence agriculture by local people
- Wood harvesting for fuel wood
- Commercial logging
- Exploitation of non-wood forest products
- Introduction of non-native plant species (especially in island TMCFs)
- Tourism and recreation that exceeds the forest’s sensitivity threshold
- The construction of telecommunication facilities and media transmitting stations that destroy the continuity of the forest
- Uncertainty about who is a legal landholder, which can lead to unlawful development of the land
Protecting and Managing the Cloud Forest
All over the world, the major obstacle to long-term cloud forest conservation is lack of awareness about and commitment to developing viable preservation strategies. It is necessary to create management processes that try to resolve existing and potential conflicts that arise when determining allowable land uses. This management process must focus on greater cooperation and participation on the local level and acknowledge concerns about developing land within TMCFs (Poore 1992). In countries like Ecuador, it will be necessary to resolve social and economic struggles in order to decrease the human impact on the natural forest.