The Cloudbridge Project: cloud forest restoration in Costa Rica

Background & Ecology
of
The Cloudbridge Project

The Cloudbridge Reserve Project aims to preserve and reforest an important gap in the cloud forest adjoining the Chirripó Pacifico river on the slopes of Mt Chirripó, the highest mountain in Costa Rica.

In the following sections we outline the project background and ecology

About Chirripó

Location. "Chirripó" derives from an indigenous word meaning "land of eternal waters." Chirripó National Park lies towards the northern end of one of the most important biological zones of all Central America. It adjoins La Amistad International Park, which covers almost all of the Talamanca mountain range and, together with adjacent reserves, includes over a million hectares and spans major sections of northern Costa Rica and southern Panama. The grouping has been designated one of the "biological hot spots" of the Meso-American Biological Corridor. The Cloudbridge reserve adds a small piece to this complex.

Flora. The flora in Chirripo National Park is one of the most complex and diverse of Costa Rica. The park owes its diversity to its wide altitude range, rising from 1500 m to 3819 m above sea level and to the unique microclimates of the Pacific and Caribbean Slopes. Part of the lower slopes have been denuded as farmers cut down trees for cow pastures or coffee plantations.

In the park we find three distinct life zones: low mountainous rain forest (cloud forest of mid altitudes), mountainous rain forest (cloud forest of high elevations), and sub-alpine rain paramo (tundra-type vegetation in the higher elevations of the range). The lower montane forest canopy reaches heights of 40 meters over the epiphyte-laden understory, where one encounters graceful tree ferns and poor man's umbrella (Gunnera talamancana ) near streams , and vines, lianas and scandent bamboo of the genus Chusque elsewhere. With increasing altitude in the high elevations, the height of the trees decreases sharply. In the highest oak forests we rarely find trees of more than 20 meters.

Stunted bamboo becomes more abundant in the paramo, above 3400 meters of elevation. Dwarf paramo vegetation is distributed along the high mountains of the tropical regions, and represents the northern limit of the Neotropical Paramos. A high percentage of the plants are endemic to this area, having adapted to the harsh climatic conditions.

We are trying to understand the composition of the lower montane oak forest so that reforestation can be done in a manner that matches the neighboring floral diversity. Common cloud forest trees include oak, cedar, elm, magnolia, figs, and a laurel called aguacatillo, which is the quetzal's principal food. Mosses, ferns, heliconias and orchids blanket the soil and trees, and the lower temperature slows the decomposition of organic matter, resulting in an accumulation of debris on the forest floor. Open areas favor pioneer species such as the Cecropia .

A key feature of mid-altitude cloud forest is the abundance of moisture-gathering epiphytes such as bromeliads and orchids. These, it seems, are vulnerable to changes in cloud levels that result from deforestation. Dr. Nalini Nadkarni conducted a study in the Monteverde reserve to determine how susceptible epiphytic species are to changes in temperature and moisture, such as the changes that appear to be taking place in recent years. She moved several epiphytes to various locations at lower elevations, outside of the reserve. She then moved the plants back to their home environment at the end of the dry season and continued to monitor their health. She found that 90% of the species died and did not recover. To ensure that the damage was not due to the disturbance of moving the plants, she conducted a control study in which she removed several epiphytes, drove them in a vehicle around the community, but then replaced them directly into their home environment rather than leaving them at the lower elevations. These plants did not demonstrate detrimental effects, indicating that the dramatic die-off was, indeed, due to living in a warmer drier climate and not due to the stress of being removed and replaced.

Fauna
The cloud forest has tremendous animal diversity. Hummingbirds are easily attracted (click on the image for the Hummingbird Cam). Birdwatchers may observe numerous species of brightly-colored birds, perhaps even the reclusive Resplendent Quetzal (Pharomachrus mocino ), or listen for the liquid song of the jilguero or Mountain Robin (Turdus plebejus ). Some birds can easily be photographed. For instance, the Collared Redstart (Myioborus torquatus), or "friend of man", is not shy; it may fly towards one's camera. Many birds, such as the redstart and the Black Guan (Chamaepetes unicolor ), are endemic to the Talamanca highlands.

Mammals are not easily seen, but the park shelters jaguars, peccaries (wild pigs), tapirs, spider monkeys, squirrels, tayras, and many other species. At left is a mono colorado or spider monkey (Ateles geoffroyi) recently spotted on the Cloudbridge Reserve. Reptile lovers can find many lizards that are endemic to the highlands, such as the spiny lizard found mostly in the paramo. Snakes, such as the parrot mountain snake, also inhabit the cloud forest, but in general, snakes are rarely seen. Insect life is abundant at lower elevations, but diminishes the higher one goes.

Costa Rica offers amazing biodiversity and opportunities for research. According to INBio , researchers know 98.8% of vertebrates (excluding fish), close to 90% of plants and 60% of fish. However, out of the most diverse group (arthropods), less than 20% of species have been described. The same goes for other invertebrates, excluding mollusks. Groups such as fungi, bacteria and virus are almost unknown, since more than 98% of expected species have yet to be described.

Geology
Chirripó National Park is located in the heart of the Talamanca Mountain Range, which was formed by various geologic processes, including tectonic movement and igneous activity. Costa Rica and Panama are of far more recent geologic origin than the countries to the north and south. These two countries lie at the boundary where the Pacific's Cocos plate , a piece of the earth's crust some 510 km wide, meets the crustal plate underlying the Caribbean. The two are converging as the Cocos Plate moves east at a rate of about four inches a year. It is a classic subduction zone in which the heavier Cocos is forced under the Caribbean plate , and one of the most dynamic junctures on earth.

Cerro Uran viewed from Cloudbridge As these two chunks of crustal material collided, the rocks of the Cocos plate were pushed downward, subjecting them to increased heat and pressure that eventually turned them into molten rock under great pressure. Because the downward thrust was at an angle to the east, when the pressure build-up finally became too much and the lava and steam moved back upward towards the surface, they did so beneath the western edge of the Caribbean plate. The result was undersea volcanic eruptions. As layer after layer of cooled volcanic material collected, the peaks finally emerged above the ocean's surface, 40-50 million years ago. In this manner, an arc of volcanic islands formed in a line parallel to and east of the zone of contact between the two plates.

Millennia passed and eruptions continued to throw more material down the slopes of the rising volcanoes. The land area filled in around their bases, until as recently as three million years ago the uninterrupted land bridge, present-day Costa Rica and Panama, was completed between northern Central America and South America, giving rise to movements of plant and animal species both north (birds) and southwards (mammals). This recent land connection to two great continents, as well as the wide range of altitudes and climates, are in large part responsible for the incredibly high biodiversity to be found in an area as small as Costa Rica.

Rock formations on the summit of the Chirripó massif indicate that some 25,000 years ago the extinct volcanic arc of the Talamancas, where it never snows, was covered by glacial ice. This glacier formed during the last of the Great Ice Ages when much of the northern hemisphere was also beneath ice, although the Chirripó glacier was not connected to those glaciers. A dozen or more small glacial lakes, piles of rounded rocks (moraines), striations on rock beds, and U-shaped valleys are all mute testimony to the existence of the former ice cover. The last glaciers retreated from this area only about 10,000 years ago.

The highlands represent the most complete evolution of the Talamanca Mountain Range's geologic characteristics . The relief forms and the lithic materials here reveal the region's geologic history, while the presence of basaltic and andesitic rocks and tuffs provide evidence of prior igneous activity. The area is not actively volcanic, but hot springs near San Gerardo de Rivas hint at the cauldron below. Earth tremors are frequent.

About the Cloud Forest

A cloud forest is a rain forest without the deluges. It is a highland forest characterized by nearly 100% humidity throughout the year. Clouds are constantly drifting through the valleys and treetops. The forest gathers water through evapotranspiration -- the accumulation of water vapors on the floor of the cloud forest and in the aerial plants known as epiphytes. The foliage harbors a wide diversity of epiphytes. Some, like "old man's beard" (the lichen usnea) draped on branches and vines, act as a huge net to capture moisture. Tree trunks are almost always covered with mosses, bromeliads, ferns, and other plants. Intact cloud forests play an extremely important role in the hydrology of certain regions of the planet; they capture, store, and filter water that feeds into local communities and large rivers hundreds of miles away.

The cloud forest exists because of the wet tropical trade winds blowing east to west from the Caribbean Sea. These moisture-laden winds are forced up the mountains, like the steep slopes shown in the picture at the top. The air cools as it rises in altitude, and the moisture is squeezed out to form water droplets which make up the almost ever-present clouds. One of the defining features of a cloud forest (as opposed to a rain forest) is that in a cloud forest most of the moisture is obtained from the clouds (horizontal mists), and a lesser amount is received as rain (vertical drops). Many hundreds of plants have evolved to depend upon this continual mist; hundreds of animals have evolved to depend on these plants. The Chirripo and Talamanca National Parks protect a large section of this precious and fragile cloud forest. In recent years, however, research has shown that this environment is even more fragile than previously known -- protecting the land within the reserve might not be enough. Studies over the last several years, notably at the Monteverde Reserve, have shown that cloud production is directly affected by downslope deforestation. Winds that blow across pastures and farmland are warmer and drier than winds that blow across forests. When warmer and drier winds rise along the slopes of the mountains on their way to the alpine forests, they must rise higher before clouds are formed. The Chirripo preserve is along the top of the continental divide: if clouds are formed higher they will be formed above, not within the forest. This will rob plants of the mists so critical to their survival. This issue has been studied extensively at Monteverde, and it is likely that cloud forests in other areas are similarly threatened.

Epiphytes in the cloud forest Because cloud forests are found in the mountains, they are much cooler than the hot tropical rainforests most people are familiar with. Mountain winds and the added weight of water-laden epiphytes often cause branches to fall to the ground. Falling branches also create light gaps, allowing the growth of light tolerant plants and producing a constant mosaic of succession.

The cloud forest topsoil or humus layer will have less natural fertilizers, meaning that the leaves that fall to the topsoil will not decompose fast enough to give nutrients back to the trees. In the rain forest for the most part the rain pours down in greater amounts and the decaying compost made out of leaves, rotten trees and other forest vegetation will have time to decompose. In the cloud forest, rain permeates the topsoil more easily; hence as a general rule trees will grow smaller than in a rain forest. This reduces the height of the cloud forest canopy and adds to the forest's gnarled appearance. Animals are abundant but the cloud forest has thicker understory foliage so that we, as visitors, are less likely to see them. Indeed birds are more abundant as well as evident in secondary underbrush and forest.

(Actually, we have found the soil on Cloudbridge to be extraordinarily rich and deep - try hiking down some of the new trails - you can plunge calf-deep in wonderful humus soil. How to explain the discrepancy between this evidence and what we have always read about the thin layer of tropical soils?)

About Tropical Forests

The tropical rainforest is earth's most complex biome in terms of both structure and species diversity. Tropical forests contain 70% of the world's vascular plants, 30% of all bird species and 90% of all invertebrates. The reason is that the tropical forest occurs under optimal growing conditions: abundant precipitation and year round warmth. There is no annual rhythm to the forest; rather each species has evolved its own flowering and fruiting seasons. Sunlight is a major limiting factor. A variety of strategies have been successful in the struggle to reach light or to adapt to the low intensity of light beneath the canopy.

Tropical Rainforests The tropical rainforest is found between 10 ° N and 10 ° S latitude at elevations below 3,000 feet. Above that elevation they become cloud forests. There are three major, disjunct groupings:

Neotropical (Amazonia into Central America)

African (Zaire Basin with an outlier in West Africa; also eastern Madagascar)

Indo-Malaysian (west coast of India, Assam, southeast Asia, New Guinea and Queensland, Australia.

The species composition and even genera and families are distinct in each region. They also differ from species of temperate forests. Species diversity is highest in the extensive neotropical forest; second in the highly fragmented Indo-Malaysian formation; and lowest in Africa. Where 5 to a maximum of 30 species of tree share dominance in the Temperate Broadleaf Deciduous Forest, there may be 40 to 100 different species in one hectare of tropical rainforest. Tropical species of both plants and animals often have very restricted distribution areas. The forests of the Neotropics are the habitat for tens of thousands of plant and wildlife species -- most of which have yet to be identified by scientists or seen by humans.

Climate: Mean monthly temperatures are above 64 ° F; precipitation is often in excess of 100 inches a year. There is usually a brief season of reduced precipitation. In monsoonal areas, there is a real dry season, but that is more than compensated for with abundant precipitation the rest of the year.

Vegetation: Biologists typically identify a vertical stratification of three layers of trees, and two layers of lower vegetation in tropical forests:

Highest layer: the emergents. Widely spaced trees 100 to 120 feet tall with umbrella-shaped canopies extend above the general canopy of the forest. Since they must contend with drying winds, they tend to have small leaves and some species are deciduous during the brief dry season.
Canopy layer: a closed canopy of 80 foot trees. Light is readily available at the top of this layer, but greatly reduced below it.
Understory: a closed understory canopy of 60 foot trees. There is little air movement in this zone so humidity is constantly high.
Shrub/sapling layer: Less than 3 percent of the light intercepted at the top of the forest canopy passes to this layer. Arrested growth is characteristic of young trees capable of a rapid surge of growth when a gap in canopy above them opens.
Ground layer: sparse plant growth. Less than 1 percent of the light that strikes the top of the forest penetrates to the forest floor. In such darkness few green plants (autotrophs) grow. Moisture is also reduced by the canopy above: one third of the precipitation is intercepted before it reaches the ground.

Growth forms: Various growth forms represent strategies to reach sunlight:

Epiphytes: the so-called air plants grow on branches high in the trees, using the limbs merely for support and extracting moisture from the air and trapping the constant leaf-fall and wind-blown dust. Bromeliads (pineapple family) are especially abundant in the neotropics; the orchid family is widely distributed in all three formations of the tropical rainforest. As a demonstration of the relative aridity of exposed branches in the high canopy, epiphytic cacti also occur in the Americas.

Lianas: woody vines grow rapidly up the tree trunks when there is a temporary gap in the canopy and flower and fruit in the tree tops of the two highest layers. Many are deciduous.

Climbers: green-stemmed plants such as philodendron that remain in the understory. Many climbers, including the ancestors of the domesticated yams (Africa) and sweet potatoes (South America), store nutrients in roots and tubers.

Stranglers: these plants begin life as epiphytes in the canopy and send their roots downward to the forest floor. The fig family is well represented among stranglers.

Heterotrophs: non-photosynthetic plants that, like animals, do not use the sun's energy to make their own food. These plants, which can live on the forest floor, include:

Parasites, that derive their nutrients by tapping into the roots or stems of photosynthetic species.
Saprophytes, that feed on decaying organic matter. Some orchids employ this strategy common to fungi and bacteria.

Common characteristics of tropical trees. Tropical species frequently possess one or more of the following attributes not seen in trees of higher latitudes.

Buttresses: many species have broad, woody flanges at the base of the trunk. Originally believed to help support the tree, it is now thought that the buttresses channel stem flow and its dissolved nutrients to the roots.

Large leaves are common among trees of the third layer. Young individuals of trees destined for the higher layers may also have large leaves. When they reach the canopy, new leaves will be smaller. The large leaf surface helps intercept light in the sun-dappled lower strata of the forest.

Drip tips facilitate drainage of precipitation off the leaf to promote transpiration and avoid accumulation of fungi. They occur in the lower layers and among the saplings of species of the emergent layer.

Other characteristics that distinguish tropical species of trees from those of temperate forests include :

Exceptionally thin bark, often only 1-2 mm thick. Usually very smooth, although sometimes armed with spines or thorns.

Cauliflory, the development of flowers (and hence fruits) directly from the trunk, rather than at the tips of branches.

Large fleshy fruits attract birds, mammals,and even fish as dispersal agents.

Fauna: Animal life in the tropics is highly diverse, and much of it is found high in the trees. Common characteristics found among mammals and birds (and reptiles and amphibians, too) include adaptations to an arboreal life (for example, the prehensile tails of New World monkeys), bright colors and sharp patterns, loud vocalizations, and diets heavy on fruits. When the trees go, so too go nature's abundant creatures. See some Flora and Fauna of Cloudbridge.

This tropical life -- this diversity of life -- is what we are trying to preserve. If you'd like to participate with a small contribution, click on the link below. Your money will go directly into reforestation.