Location and General Description
This ecoregion's combination of significant elevational changes, climatic variations and central location along the land bridge between North and South America provides it with tremendous biological richness and endemism. Located in the highlands of Costa Rica and western Panama, the Talamanca Montane forests ecoregion occurs above 750 m and above 1,500 m in some places on the Pacific slope, up to approximately 3,000m, where they grade into páramo grasslands. The rainfall and temperature in this area of Central America is a direct result of the elevation and orientation north or south side of the mountain range. The average temperature and rainfall for this part of Costa Rica varies from 25° C and 2000 mm at the Caribbean Sea level to –8° C and >6000 mm at the highest pecks including Cerro Chirripo the highest point in southern Central America at 3,820 m. The high humidity and precipitation which averages between 2,500 - 6,500mm each year, steep slopes, and cool temperatures have limited agricultural and urban development, making these highland moist forests one of Central America's more intact ecosystems.
This southern portion of Central America is in a zone of tectonic plate convergence, where two small oceanic plates are being driven down below the Caribbean continental plate. These geologic movements resulted in tectonic instability, the uplifting of the Talamanca Range over 15 million years ago, and the fusion of South and North America 3.5 million years ago. They continue producing seismic and volcanic activity in the region (Clark et al. 2000); however these mountains are not a result of volcanic activities, resulting in their status as the highest and widest non-volcanic mountains in Central America. This ecoregion was also shaped by ancient glaciation, which has left areas with cirque lakes and steep sided valleys of more than a 60° pitch in places. Within this ecoregion, these glacial remnants are the only signs of glaciation in Central America. The dominant soil type is poorly evolved inceptisols formed due to the continual leaching of minerals from the soils by the high influx of water.
The forest habitats of this ecoregion include Atlantic slope "aseasonal" rain forest, Pacific slope seasonally dry but mostly evergreen forest, and "perpetually dripping cloud forest" on the mountain tops, above approximately 1500 m (Haber 2000). The high annual rainfall, wind-blown mist, and frequent presence of clouds, probably the most outstanding characteristic of these montane forests, produce a lush, dense forest with a broken canopy and high species diversity. Abundant epiphytes cover tree branches, and tree ferns are common. Dominant tree groups include the Lauraceae family, especially in the northern section of the ecoregion, and endemic oaks (Quercus spp.), especially in the south. The unique oak forest stands in this ecoregion are characterized by majestic, tall trees (up to 50 m tall), heavily dominated by two species: Quercus costaricensis and Q. copeyensis, while Magnolia, Drymis, and Weinmannia are also important tree elements. The understory is characterized by the presence of several species of dwarf bamboo (Chusquea). Higher peaks and ridges exposed to moisture-laden trade winds support an elfin, or dwarf forest characterized by thick mats of bryophytes covering short, dense gnarled trees (Haber 2000).
The separation of these highland habitat "islands" from other mountain ranges and their location in this land bridge between North and South America have encouraged both the mix of northern and southern species and the rise of endemic species in all taxa. The striking variety of vegetation types across steep elevational gradients and among the various mountain massifs in this ecoregion have produced very high regional plant biodiversity (high beta diversity) (Haber 2000). The Talamanca Range alone is estimated to contain about 90 percent of Costa Rica's known flora. La Amistad International Park, which contains protected area in both countries, contains some 10,000 vascular and 4,000 non-vascular plant species, including several hundred endemic plant species (Davis et al. 1997). Forests above 1200 m in Costa Rica's Monteverde reserve complex in the north of the ecoregion support 1,708 species of plants, including over 440 species of trees. This high richness is due in large part to its great diversity of orchids (291 species), ferns (175 species), and other epiphytes (Haber 2000). Over 30% of the ecoregion's flora and over 50% of the high mountain flora of Costa Rica and western Panama is considered endemic to those zones (Davis et al. 1997).
Similarly, over half the avifauna of the highlands of Costa Rica and western Panama is endemic to this region (Stiles 1985). Almost 85% of the species with restricted geographic ranges are dependent on forest; most of these are species endemic to the Costa Rica-Chiriqui highlands (Stiles 1985). Endemism among amphibians is also high (Young et al 1999), and at least seven small mammals are considered regional endemics (Palminteri et al. 1999, adapted from Reid 1997),
Earthquakes, volcanism, and landslides (triggered by torrential rains or earthquakes) are the major natural disturbances influencing the montane forest structure (Clark et al. 2000). The resulting steep slopes and poor soils have made the habitats of this ecoregion some of the most intact in Central America. The La Amistad International Park, one of the largest reserves in Central America, consists of over 400,000 ha of relatively intact montane forest. These larger blocks of intact forest are essential for preserving remnant populations of harpy eagles (Harpia harpyja) and they protect breeding grounds of threatened and endangered birds endemic to the highland forests of this ecoregion, such as: resplendent quetzal (Pharomacrus mocinno), three-wattled bellbird (Procnias tricarunculata), bare-necked umbrellabird (Cephalopterus glabricollis), and black guan (Chamaepetes unicolor). The first three of these birds migrate seasonally to lower elevations, demonstrating the importance of not only maintaining intact highland habitats but also connecting them to neighboring intact middle and lower elevations. In fact, over 65 (> 10%) of the birds found here migrate altitudinally (Stiles 1985).
The Atlantic middle elevations also contain some of the rarest butterfly species in Central America and some of the world's highest butterfly species richness (DeVries 1987). Populations of crested eagle and painted parakeet were recently discovered in Cerro Hoya on the Azuero Peninsula (Delgado 1985).
The Talamanca ecoregion still maintains almost 75% of its original forest cover (DGF 1989; ANAM [INRENARE] 1992), which is distributed patchily over the isolated highland zones of the Tilaran and Talamanca ranges. The largest block occurs in and around the La Amistad Biosphere Reserve. Deforestation, even in the Talamancan highland oak forests, has proceeded since the 1950s at an "alarming" rate (Kappelle 1996). The endemic oak species are also valued for their excellent properties to make charcoal, while rare tree species such as Podocarpus are very sensitive to exploitation.
The Talamanca montane ecoregion's high biological diversity and endemism (Stiles 1985; Delgado 1985; Davis et al. 1997), as well as its steep topography have encouraged the Costa Rican and Panamanian governments to establish a series of reserves with varying degrees of protection. A full 40% of the ecoregion is under strict protection, in national parks such as the La Amistad, Chirripó, Braulio Carrillo, Volcán Poas, and Rincón de la Vieja, and the Monteverde cloud forest reserve complex. Like most protected areas in Mesoamerica (Boza 1996; Powell pers. comm.), the montane parks of the Talamanca forest are small, lack connection or planning, and do not represent the entire range of ecosystems needed to support altitudinal migrants (Stiles and Skutch 1989) or respond to the possible effects of climate change. For example, they do not allow for altitudinal movement of species. Even La Amistad protects primarily highland habitats over 2,000m while largely missing Pacific slope middle and lower elevations.
Types and Severity of Threats
Despite the steep slopes and poor soils of these forests, continued illegal logging, squatting, and clearing of land for cattle pasture are making small in-roads into the remaining large forest blocks, reducing connectivity among habitat blocks within the ecoregion and between it and neighboring ecoregions. Kappelle (1996) cites the conversion of oak forests to pasture and cropland as the primary cause of erosion in the Talamancan highlands; compaction by cattle of the soil on steep slopes exacerbates the problem, causing runoff and loss of both soil and water resources.
While the Talamanca Montane forest is relatively well protected, the recent but drastic elimination of middle elevation habitats in surrounding ecoregions has isolated the highland reserves and made their populations vulnerable to genetic degradation. Furthermore, cloud forests are particularly sensitive to climate change (Pounds 1999), and their location on mountaintops leaves them little chance for adaptation to climatic shifts. Many montane amphibians, such as Monteverde's golden toad (Bufo periglenes), have disappeared from some or all of their ranges for reasons still undetermined by science (Pounds 2000). Maintaining and restoring forest cover in more than just the highest elevations will benefit populations and ecological processes in both the short and long terms but must be supplemented with research on impacts of regional and global human activities on montane systems.
Justification of Ecoregion Delineation
The montane forests of the Talamanca and Cordillera Central of Costa Rica and Panama are host to a diverse and unique association of flora and fauna – which share components with both North and South America and of the Caribbean and Pacific slopes. Many endemic species are found here, and this archipelago of montane habitats hosts high levels of beta-diversity and endemism. Our linework follows Tosi’s (1969) Holdridge Life Zones – and encompasses the premontane rain forest, lower montane rain forest, montane rainforests, small patches of subalpine rain páramo, and all other lize zones enclosed in this broader matrix. In Panama our linework follows UNDP (1970) to include the lower montane wet forest, lower montane rain forest, montane wet forest, montane rain forest, premontane rain forest, and premontane wet forest life zones.
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Prepared by: George Powell, Sue Palminteri, and Jan Schipper
Reviewed by: In Process