Biodiversity of the Caribbean A Learning Resource Prepared For: (Protecting the Eastern Caribbean Region’s Biodiversity Project) Photo supplied by: Jennifer Goad Part 2 / Section E Tropical Forest Ecosystems February 2009 Prepared by Ekos Communications, Inc. Victoria, British Columbia, Canada [Part 2/Section E] Tropical Forest Ecosystems Table of Contents E.1. Introduction E.2. The Forests of the Caribbean E.2.a. Dry Limestone Forests E.3. Tropical Rainforests E.3.a. Cloud Forests E.4. Structure of a Forest E.5. Deforestation E.6. Conservation, Protection and Restoration of Tropical Forests E.7. Case Study: Central Forest Range National Park (CFRNP), St. Kitts E.8. Activity 1: Letter to the Editor E.9. Activity 2: Exploring Tropical Rainforests E.10. Case Study: Land of Wood and Water, Deforestation in Jamaica E.11. Activity 3: Take Action to Conserve Tropical Forests E.12. Case Study: Regenerating the Dominican Dry Forest References E.13. Case Study: Alexander Skutch Biological Corridor, Costa Rica E.14. Activity 4: Biodiversity Story Time E.15. Activity 5: Case Comparisons E.16. References [Part 2/Section E] Tropical Forest Ecosystems E.1. Introduction Life is difficult in the Caribbean, if you are a tree. A number of An ecoregion is a “relatively large unit of land containing conditions transpire to make it so. The islands are small and most distinct assemblage of natural communities and species, are heavily populated. To meet the needs of the region’s growing with boundaries that approximate the original extent of 4 population, forests are cleared to make way for settlements and natural communities prior to major land use change.” Not agriculture, but loss of forest ecosystems produces unintended only do ecoregions provide a useful tool for classifying com- consequences that often come at a cost to human welfare as well munities of species and their environment, but they also can as to biodiversity. On top of disturbances caused by humans, be applied to the preservation and conservation of biodi- forests must also cope with hurricanes, heavy rains, landslides, versity. and the like. The forests need to be protected and conserved; where they are Tropical and subtropical coniferous forests are the most not, deforestation typically leads to such impacts as soil erosion, restricted of forest types within the region, occurring primarily loss of habitat for wildlife, or alterations in the water balance in Cuba and Hispaniola Island. On the latter island, this type of (flow of water in and out of a watershed). These can combine to forest occupies about 15% of the land, either on the lower slopes make human habitation of an area very difficult, and sometimes of mountains (850 – 2200 metres elevation) or on relatively flat impossible. areas higher up (2100 – 3175 metres elevation). As such, they constitute the only forest type to exist above 2500 metres. Among the Caribbean islands, the remaining forests cling to a perilous and tenuous existence because of past mismanagement Not surprisingly, each forest type requires specific management and increasingly high demands for benefits derived from these strategies, and these must be crafted with care. Because of the forests. The situation leaves very little room for error in decisions small size and steep slopes of the Caribbean islands, many forest affecting forest preservation and use. types may only be found in a small area, which presents an added challenge for forest management. E.2. The Forests of the Caribbean At present, the region’s forests cover approximately six million E.2.a Dry Limestone Forests hectares or 26% of its land1 and vary widely in composition. Dry limestone forests form a large part of many of the Caribbean According to the terrestrial ecoregions of the world, they can island ecosystems. These dry forests are found in the rain shadow be generally classed as tropical and subtropical moist broadleaf of mountains and along coastlines where soils are often poor, forests, tropical and subtropical dry broadleaf forests, or tropical and typically receive less than 1000 milimetres of rain annually. and subtropical coniferous forests. The tree canopy is usually low (8 – 12 metres or 20 - 35 feet), and the trees themselves are spindly and slow-growing due to the Tropical and subtropical moist forests occur throughout the lack of rainfall. During the dry season, which normally lasts from Caribbean. They are classified according to the altitude they are December to July, some trees will drop their leaves to better sur- found (lowland to montane) and the amount of precipitation they vive long periods without rain. Other plants have water storage receive (wet to rainforest). Originally this forest type covered ap- structures, such as thick trunks and waxy coatings on their leaves, proximately 85% of Jamaica, 60% of Hispaniola Island (Domini- trunks, and branches, which help keep moisture in. The forest can Republic and Haiti), 85% of the Leeward Islands, 70 – 95% canopy is largely evergreen, dominated by Gymnanthes lucida of the Windward Islands, and 90% of Trinidad and Tobago2. (Euphorbiaceae) in areas of limestone soil, while the emergent Throughout the range of this forest type, the average annual layer is more deciduous. Thick growths of climbers, vines, and rainfall varies between 750 milimetres to an astonishing 10,000 strangler figs are sometimes found where more soil is present. milimetres! This mind-boggling amount of rain has been record- ed in the interior highlands of Dominica, one of the Windward These forests and scrublands are important habitats for many Islands. These islands feature some of the most biologically rich unique bird and plant species. Wander through these forests and and diverse moist forests within the Caribbean because their rug- you’ll come across a variety of species adapted to the dry terrain, ged terrain not only intercepts moisture-laden Atlantic air masses, including iguanas, butterflies, and hummingbirds. Thorny tree it inhibits human development. species such as acacias and logwood are common., Tall, upright cactus and thatch palms — as well as agaves, which are attrac- Tropical and subtropical dry forests also exist throughout tive to orioles and hummingbirds — grow in clear, unsheltered the entire Caribbean but not nearly to the same extent. They areas. White-crowned pigeons, Caribbean doves, parakeets, hum- once covered 15% of Jamaica, 20% of Hispaniola Island, 5% of mingbirds, vireos, and warblers are found year-round. In Jamaica, Trinidad and Tobago, and very small portions of the Leeward and the endangered Jamaican iguana is restricted to dry forests in the Windward Islands3. These forests are typically found between Hellshire Hills outside Kingston. An endemic tree frog and the the coasts and the mountains, where the average annual rainfall Jamaican boa (Epicrates subflavus) are also restricted to these dry rarely exceeds 1250 milimetres. forests. [Part 2/Section E] Tropical Forest Ecosystems The machineel tree (Hippomane manicella) is widespread throughout the Caribbean. It thrives in dry regions close to the Examples of Caribbean Cloud Forests shore. The sap of this tree is highly irritating to the skin, and so toxic that native populations used it to coat the tips of their poi- • Nevis Peak (St. Kitts) son arrows. Iguanas happily eat its fruits but they are poisonous • Blue & John Crow Mountains National Park to people. Even rainwater that passes over the tree’s leaves can (Jamaica) irritate the skin. • Santa Elena & Monteverde Cloud Forests (Costa Rica) E.3. Tropical Rainforests The term rainforest is a very imprecise. Most attempts to define For videos links about Cloud Forests visit: it have relied upon the amount of rainfall. Unfortunately, there is video.google.com/videosearch?client=safari&rls no consensus as to what that amount should be. The lowest limit =en-us&q=Cloud+Forests+Costa+Rica&ie=UT for the average annual rainfall is 1000 milimetres; the highest is F-8&oe=UTF-8&um=1&sa=X&oi=video_result_ 4000 milimetres. What is not in dispute is where rainforests are group&resnum=4&ct=title# found: between the Tropic of Cancer and the Tropic of Capricorn. In other words, near the Equator. Also not in question is that rain- forests clearly belong to the tropical moist broadleaf forest type E.4. Structure of a Forest within the Caribbean region. Generally, forests can be thought of as having five distinct layers: overstory (emergent), canopy, understory, shrub layer, and A tropical rainforest has more kinds of trees than any other forest forest floor. Each layer has its own unique assemblage of plant type in the world. In fact, 70% of the plants in rainforests are and animal species. The overstory refers to the crowns of the trees. emergent trees which tower above the canopy of the other trees. These trees can attain heights of 30 metres or more. The roof of E.3.a. Cloud Forests the forest or canopy is formed by the branches and foliage of the Tropical montane cloud (or mist) forests are a rare type of closely-packed trees. The understory consists of more widely- mountain forest found in tropical areas where local climatic con- spaced and smaller tree species as well as regenerating canopy ditions cause cloud and mist to be regularly in contact with the and overstory species. It is shielded from harsh, intense sunlight, forest vegetation. They are a subtype of the tropical and subtropi- drying winds, and heavy rainfall. Still younger, juvenile trees cal moist forests. and shrubs make up the next layer while the forest floor is cov- ered with litter from the canopy above, along with flowers, ferns, fungi, and mosses. Among the Leeward and Windward Is- lands, where the rainforest is relatively undisturbed, the overstory or emergent layer consists largely of the gommier (Dacryodes excelsa). On the latter islands, the gommier tree is frequently found in association with bois rouge (Amanoa caribaea) and bois côte (Ta- pura antillana) which form the canopy.