Geographic Location: In southern Costa Rica near south-western Panama, the park mainly between 8º27'-8º39'N and 83º25'-83º45'W.
Area: Park main sector 424 km2, Bosque Esquinas sector 148 km2; peninsula c. 2330 km2.
Altitude: 0-745 m.
Vegetation: Mostly tropical wet forest, also tropical premontane wet and rain forests; associations include marsh, mangrove and swamp forests, alluvial plains forest, cloud forest.
High diversity: 4000-5000 vascular plant species on peninsula, over 500 tree species in park. From recent fieldwork, 30 species and genus Ruptiliocarpon (Lepidobotryaceae) new to science. Phytogeographically unusual: species with various disjunct distributions.
Useful plants: Genetic reserve for species economically and/or ethnobotanically recognized (e.g. timbers, industrial chemicals, medicines, fruits), and for species with such potential.
Social and environmental values: Rich faunal diversity (two new insect genera recently discovered); threatened species; scientific benchmark; watershed protection; scenery, ecotourism.
Threats: Logging, access from an expanding network of roads, hunting, mining, squatters, tourism without adequate regulation.
Conservation: National park, adjacent forest and Amerindian reserves; regional Conservation Area: integrated land-use planning for peninsula's general development.
The Osa Peninsula is a boot-like landmass of southern Costa Rica's Puntarenas Province, projecting eastward toward bordering Panama 40 km away. The main sector of the park covers nearly 418 (to c. 437) km2 along the outer base of the peninsula, 150 km south-east of Costa Rica's capital San Jose.
The peninsula was considered remote, and apart from the mainland due to initial mangrove forests, rough uplands and a freshwater swamp; it has become a directly engaged, developing frontier. The region's very wet natural systems evolved in partial isolation from the broadly drier tropical Pacific Coast.
Within the park is the drainage of Corcovado Basin, a broad sediment-filled oceanic embayment between Punta Llorona and Punta Rio Claro (near Sirena), which extends inland from the Pacific Ocean 2-10 km eastward. The basin's low plain covers c. 100 km2 through which meander several rivers, and is rimmed except to the west by uplands (often below 500 m), which increase in altitude and irregular relief from an undulating plateau (below 200 m) in the north-west part of the park (north of Llorona), to 745 m in the south-east on the peninsula's highest cerros, Rincon and Mueller.
The rugged uplands, produced by intensive tectonic activity and weathering (including frequent landslides), are dominated almost throughout by eroded narrow ridges and long steep slopes, with dense drainage networks (Tosi 1975; Herwitz 1981; Hartshorn 1983).
The Corcovado plain, which was formed in the Pliocene- Pleistocene, is composed of alluvial deposits and mollisol soils. The mountainous areas are composed of Late Cretaceous volcanic and sedimentary rocks; gold has deposited in many hillsides and streambeds; the soils are inceptisols and entisols. A virtually uninterrupted sandy beach extends for 20 km, with cliffs and pocket beaches at the northern and southern park headlands; there is a marine cave near the southern point.
Up to ten tremors a day sometimes occur in the region, and crustal elevations have been observed. Seaward, the Cocos crustal tectonic plate descends beneath the Caribbean plate at the rate of a few cm per year (Boza and Mendoza 1981; Janzen 1983; Lew 1983; Gomez 1986).
There are few meteorological records from Corcovado National Park (Herrera 1986; Coen 1983; Herwitz 1981).
The mean annual rainfall is estimated at 3000-3800 mm on the plain and 4000-5000 mm in the uplands, to 5500-6000 mm or more on the highest cerros (cf. Boza 1988; Hartshorn 1983). The c. 9-month rainy season's rainiest period is September-November; windstorms occur, rarely of tornado force (Janzen 1983; Boza and Mendoza 1981). The soils are completely saturated for c. 9-12 months of the year.
The dry season is about (December-) January through March, with just a few rainy days per month, but the humidity stays high - although there is enough drying that in February-March set fires can be maintained (Janzen 1983; Jones 1990). The mean annual temperature may be 26º-27ºC near the coast (varying daily by as much as 10ºC) and 21º-23ºC on the cerros, with March-May warmer and November-January cooler. The estimated daily sunshine averages 5 hours per day throughout the year, varying from 8 hrs a day in February and 6 hrs a day in January and March-May, to just 3-4 hrs daily in June-November.
Corcovado National Park and adjacent areas conserve the most important tract of lowland tropical wet forest still extant on the Pacific side of Central America (Hartshorn 1983; WWF-US 1988). The Corcovado plain in the Holdridge life-zone system is classified as tropical premontane wet forest - warm transition; the evergreen upland forest covering almost half the park is tropical wet forest, and the highest cerros probably harbour tropical premontane rain forest. During the region's c. 3-month dry season, the humidity stays unusually high and few species are deciduous. In certain areas (e.g. Cerro Rinc�n), epiphyte abundance may reach high levels similar to those for example at La Selva Biological Station on the Atlantic slope in central Costa Rica (in CPD Site MA16, see Braulio Carrillo-La Selva Region Data Sheet). The park's uplands can be considered the climatic association, whereas the plains comprise several edaphic and hydric associations (Hartshorn 1983). The rainy winds between May and August provoke many tree falls.
Some thirteen ecosystems have been discerned within the park (in the following account, proceeding essentially inland and upward) (Tosi 1975; Vaughan 1981; Boza and Mendoza 1981). With more research, 25-30 associations may become determinable (Hartshorn 1983; Gomez 1986), including vegetations of the coastal strand, cliff and rock faces, landslips and waterfalls. Some of the main ecosystems and associations are:
a. Mangrove swamps (with the tallest trees to 30 m). Up to five tree species occur, including Pelliciera rhizophorae (cf. Jimenez 1984) and Rhizophora racemosa, as well as Crinum erubescens and C. brevilobatum (FNT 1992).
b. Corcovado Lagoon, which each rainy season is infused with up to 1 m of standing fresh water, and supports a floating central mat of ample herbaceous vegetation including Eichhornia crassipes, Pistia stratiotes, Salvinia sp. and Utricularia spp. (FNT 1992).
c. A herbaceous marsh c. 50 cm in height and 10 km� in expanse bordering the lagoon, with Hymenachne sp., Panicum maximum, Ludwigia sp., Polygonum sp. and Aeschynomene sp.
d. A palm swamp (jolillo forest) in a band around the marsh, dominated by virtually pure stands of Raphia taedigera, which has leaves nearly 15 m long (Devall and Kiester 1987).
e. Varied swamp forests, for example peripheral to the palm swamp at first with Andira inermis, Carapa guianensis, Crateva tapia and Luehea seemannii, and beyond large well-buttressed canopy trees, stilt-rooted subcanopy trees and a fairly open palm understory (Crysophila guagara, Prestoea decurrens), commonly including the trees Carapa guianensis, Erythrina lanceolata, Grias fendleri, Mouriri sp., Pterocarpus officinalis and Virola koschnyi. On particularly poorly drained alluvium and estuaries are lower forests, for example with Mora oleifera (which has the largest dicot seed - averaging c. 500 g), Pterocarpus officinalis (Janzen 1978), Hasseltia new sp. and Pachira aquatica.
f. Gallery forest on well-drained alluvial flats and terraces, with giant Anacardium excelsum (to 50 m tall and 3 m in dbh) and other large trees of Caryocar costaricense, Hernandia didymantha, Pterygota excelsa, Terminalia oblonga and Ceiba pentandra - an epiphyte-rich emergent of this species on the plain is possibly the largest tree in Central America, at over 70 m or even 80 m tall and over 3 m in diameter above buttresses 10 m high (Boza 1978, 1988).
g. Plateau forest: awe-inspiring with the very high density of large trees (a Vantanea barbourii was 65 m tall and 2 m in dbh). Other common trees include Anaxagorea costaricensis, Aspidosperma spruceanum, Brosimum utile, Calophyllum longifolium, Carapa guianensis, Caryocar costaricense, Chrysochlamys sp., Couratari guianensis, Minquartia guianensis, Qualea paraense, Symphonia globulifera, Tetragastris panamensis, Trichilia sp. and Welfia georgii.
h. Mountain or uplands forest: this extensive, 5- stratum ecosystem has a high diversity of species (c. 100-120 tree species per ha), very tall canopy trees (many over 50 m) sometimes unbranched up to 35 m or with spectacular buttresses, and abundant palms (Iriartea deltoidea, Socratea exorrhiza), lianas and vines. The absence of dominance is characteristic among the common tree species, which include Ardisia cutteri, Aspidosperma spruceanum, Brosimum utile, Heisteria longipes, Poulsenia armata and Sorocea cufodontisii. A site found north of the park (c. 5.5 km west of Rincon de Osa) had 22 species over 50 m tall, 5 over 60 m and an emergent of Minquartia guianensis that reached 73 m. On narrow ridges, Brosimum utile and Scheelea rostrata are characteristic; trees can still grow large, when well-anchored upon both sides of a ridge (e.g. Caryocar costaricense, Peltogyne purpurea).
i. Cloud forest, with many epiphytes, tree ferns (perhaps Cnemidaria choricarpa, Cyathea trichiata), Quercus spp. (e.g. Q. insignis, Q. rapurahuensis), Alfaroa guanacastensis, Oreomunnea pterocarpa and Ticodendron incognitum (FNT 1992).
Few places on earth have so much biotic diversity in such a small geographic area (Vaughan 1981), partly because of Costa Rica's role as a corridor for flora and fauna from north and south. So far over 1510 vascular plant species in 707 genera of 154 families have been documented (FNT 1992). There is an unusual mix of species on the peninsula, with their next closest population or related species far away (B.E. Hammel 1993, pers. comm.).
The Pacific lowland wet forests of Costa Rica have strong floristic affinities with the Choco of north-western South America (CPD Site SA39, see Data Sheet) as well as the Venezuelan Amazon, and also have elements of the Guayanan flora that may have arrived before formation of the Panamanian isthmus (Gomez 1986). Primarily South American genera that reach their limit on the peninsula include Huberodendron, Newtonia, Paramachaerium, Tachigali, Uribea, Williamodendron, Chaunochiton and Oenocarpus. There also are distinctive relationships: (1) with Costa Rica's mainland flora, where shared species are either at higher elevations (e.g. Oreomunnea pterocarpa, Ticodendron incognitum) or on the Atlantic slope (e.g. Ruptiliocarpon, which was recently discovered, in a family previously considered African); and as well with (2) Jamaica (Ziziphus chloroxylon), and with (3) several countries to the north, even as far as Mexico (e.g. Recchia simplicifolia).
The low-altitude cloud forests have unusual biogeographical characteristics and high endemism (FNT 1992). Perhaps 2-3% of the peninsular flora will be found to be endemic, which includes 25% endemism in Marantaceae, and the rare Osa pulchra (Rubiaceae). The Corcovado uplands forests undoubtedly have the greatest tree-species diversity in Central America - the park harbours at least 500 tree species (Hartshorn and Poveda 1983), a fourth of the tree species in all of Costa Rica (Boza 1988; Boza and Mendoza 1981).
The great breadth and depth of scientific knowledge accumulated about Costa Rica's natural wealth through decades of international and national efforts, including many significant studies within the park region (cf. Janzen 1983; Boza 1988), have made the park increasingly prominent for more complex and long- term biological and ecological research. The government in 1989 established a National Biodiversity Institute (INBio) to strongly accelerate both a complete national inventory (in 10 years) and investigation on the utility of the Costa Rican flora and fauna (Brandon and Umana 1991; Jones 1990). The park region has been chosen as one of the first areas for an intensive inventory.
INBio has placed early emphasis on seeking pharmacological properties (Sittenfeld-Appel 1992). Locally a number of species provide medicinals, e.g. from seeds, bark or wood: Quassia amara, Simaba cedron, Bursera simaruba, Hymenaea coubaril and Bauhinia manca; from latex: Brosimum utile and Ficus spp.; and from the wounded trunk of Copaifera camibar, cam�bar oil, which is extracted for trade.
Other commercial products include fibres for handicrafts, from the bark of Apeiba tibourbou and the aerial roots of climbing aroids and Cyclanthaceae. The region is a natural genetic reserve for example for Persea americana (avocado), Byrsonima crassifolia ("nance") and Licania platypus ("sonzapote"). The fruit of Hymenaea coubaril ("guapinol") may have major potential for sustainable extraction; the delicious pulp is edible and can be used in cakes and drinks, and the fruits are abundant (up to 45 kg per tree fall per day in February and March) and store well. Other non-timber products with economic potential are natural chewing gum (Manilkara staminodella), edible nuts (Sterculia mexicana), palm heart (Iriartea) and cosmetic oil (Carapa guianensis). Osa pulchra may have ornamental potential.
The Copenhagen Botanical Museum (K. Thomsen) in collaboration with Costa Rica's Fundaci�n Neotr�pica in 1992 initiated a study of the potential for non-timber forest products from the Osa Peninsula. The research is determining uses of the species as known locally and elsewhere, ecological quantification (both inventory and natural production), extractive potential and possible conflicts between extraction of the non-timber forest products and timber harvests.
Only 2000 km2 of forests in Costa Rica might remain as of 1993 for the exploitation of timber - the 400-600 km2 deforested yearly since 1977 is the fastest per capita conversion of any Latin American country. Timber in non-protected areas is likely to be gone before the year 2000 and Costa Rica may start to import lumber by 1995 (Gomez and Ugalde 1988; Tangley 1986; Omang 1987; Jones 1990). Tree replanting has already begun on the peninsula. The genetic stocks of many tree species in the park are increasingly valuable for critical reforestation or afforestation efforts (cf. Herwitz 1981).
Social and environmental values
The park protects various threatened plant and animal species, and is known to have about 124 species of mammals (over 50 bats); 375 species of birds (perhaps 5-8 endemics); 117 species of reptiles and amphibians (2 crocodilians, 4 sea turtles); 66 freshwater fish species; and 70 species of marine crabs (FNT 1992; Boza 1988; Janzen 1983).
Among the mammals are 4 monkey species (e.g. Central American squirrel monkey, white-faced capuchin), anteaters, sloths, southern river otter, crab-eating racoon, 5-6 cat species (e.g. ocelot, margay, jaguar), peccaries and northern tapir.
The birds include the country's largest population of scarlet macaws, the horned guan and possibly still the harpy eagle. The region is within the Southern Central American Pacific Slope Endemic Bird Area (EBA A17), which has 16 restricted-range species. At least 9 of them occur on the Osa Peninsula, of which the mangrove hummingbird (Amazilia boucardi) and yellow- billed cotinga (Carpodectes antoniae) are considered globally threatened and three others nearly threatened (Stattersfield et al., in press).
The Osa Peninsula harbours the most intact tropical lowland ecosystem for insects from central Panama to Mexico, with 6000-10,000 species - including certain bees, butterflies and beetles that need large areas to survive. Within the park are c. 6000 insect species, among them at least 220 species of butterflies (Janzen 1983; Boza and Mendoza 1981).
In the park are portions of the upper watersheds of the Rincon and Tigre rivers, which are important for the water supply of lowland communities. National and international tourism to the park is increasing, since it has become more accessible by a good road onto the peninsula to Puerto Jimenez, secondarily extending to Carate near the park's south-eastern boundary, and with the regular arrival of cruise ships. In the early days scientists were over 90% of the annual visitors (Cahn and Cahn 1979; cf. Wille-Trejos 1983); the growth of registered visitors increased from 324 in 1980 to 7863 in 1992, 80% of whom were from abroad.
Gold mining is a recurrent difficulty. There was a crisis a few years ago, with an influx of gold panners and some miners using more destructive modern methods of extraction from streambed alluvial deposits. The region had undergone a gold rush in the 1930s (Boza and Mendoza 1981) and in c. 1980-1985 the park was invaded by 1000-3000 people (mining squatters with their families) because of Costa Rica's troubled economy (especially the loss of local wages when banana prices dropped) and a rising price for gold (Tangley 1986; Wallace 1992). Dams, canals, even tunnels were made, and the mined tailings (soil sediment, some mercury) severely polluted aquatic ecosystems in the southern third of the park. Also, animals were sought by the influx of miners as well as other hunters and farmers and had already declined severely before 1975; they were virtually absent from the park's southern third - perhaps interrupting seed dispersal of some tree species (Tangley 1986). In 1986 the miners were relocated; restoration work and slow recovery are continuing (Wallace 1992; Jones 1990; WWF-US 1988; Tangley 1986; cf. Boza and Mendoza 1981). Outside the park's boundaries modern mining goes on, for example just to the east.
Logging had occurred within the park area, and the sporadic removal of select trees is an ongoing risk. A major international operation was close to beginning in late 1975, when the park was established. The timber was estimated to have been worth more than the park's gold (Cahn and Cahn 1987). Beyond the park on the peninsula, deforestation first became significant between 1977 and 1983 (Gomez and Ugalde 1988). Already one third of the forest is gone, and each year c. 10 km2 more are cleared. The government's Institute of Agrarian Development (IDA) distributes land rights to those who will work the land, including tracts from a third (233 km2) of the neighbouring Golfo Dulce Forest Reserve, which regulates logging and tries to prevent the spread of slash-and-burn agriculture (Jones 1990).
Without sustainable development that is supported by the Costa Rican economy, the park will remain threatened: an oasis in a rising sea of societal pressures (Gomez and Ugalde 1988; Cahn and Cahn 1987; Lewis 1982). Meagre funding for the park and buffering forest reserve critically threaten both the capabilities to manage the planned maintenance and improvement of this rather new national park (Torres and Hurtado de Mendoza 1988; MacFarland, Morales and Barborak 1984; Vaughan 1981) and to deal with intensifying societal stresses (Wallace 1992; Jones 1990; WWF-US 1988; Omang 1987). Logging and mining roads have been built beyond the park; a side road approaches the park's mid-northern boundary and a road may be built to Drake Bay near the park's north-western boundary.
The presence of yellow fever probably preserved the region from conversion to ranches and farms long ago (Carr and Carr 1983), and the absence of a road until recent years helped preservation. National and international organizations in 1962 began more intensively studying the flora, fauna and ecology of the Osa Peninsula. A wave of interest that arose in 1971 to establish a large protected area and the subsequent efforts were answered in October 1975, when the government established Corcovado National Park in response to the various escalating threats. In 1976, 100-300 families of settlers were relocated, and their cattle and pigs were removed from the Corcovado plain in 1978. Their (5-) 20-30 km2 of pastures and croplands and 1-4 km2 of under-cut forest (where the colonists had cut the undergrowth preparatory to felling and sowing for conversion to pasture), along with older degraded patches scattered through the plain, are recovering to diversified forest (cf. Herwitz 1981). The park was enlarged over 20% in 1980 to provide somewhat more natural boundaries and include part of the highlands of the peninsula (Boza and Mendoza 1981; Wright 1976; Hartshorn 1983), and the Bosque Esquinas sector which has a 2-km wide marine portion was recently established (see Site Map when available).
The government in 1987 began to integrate park management and community outreach for the country by means of nine regional Conservation Areas (ACs), which merged each key protected area and adjacent buffer zone into a developmental whole, within a National System of Conservation Areas (SINAC). The Osa Conservation Area (ACOSA) combines Corcovado NP (now 572 km2) and the Golfo Dulce Forest Reserve (592 km2) into unified work striving with local communities to define how to implement activities that are ecologically and economically sustainable (Brandon and Umana 1991). An Amerindian reserve (27.1 km2) for the Guaymi is adjacent to the park to the north. About where the peninsula meets the mainland to the west is Manglar Sierpe-Terraba Forest Reserve (227 km2). One third of the peninsula is private land, which includes some ecotourism reserves; just 97 km2 of IDA's available land is regarded as adequate for farming (only by working large, 20-ha parcels).
In 1988 an ecodevelopment program (BOSCOSA) was initiated by Costa Rica's Fundacion Neotr�pica and the World Wildlife Fund-US (WWF-US) to improve matters on the peninsula, for example in the Golfo Dulce Forest Reserve where c. 5000 families live and in the Guaymi reserve where there are 24 indigenous families (and a few in-holdings). The BOSCOSA efforts include research, training, sustainable community forestry, natural forest management, land purchase, reforestation, agroforestry, cultivation of ornamentals, environmental education (including a Tropical Youth Centre), artisanry and ecotourism (Cabarle et al. 1992).
Work in conservation has received support from among others Conservation International, The Nature Conservancy (partly by means of its Parks in Peril campaign), WWF-US, rain-forest conservation groups in several countries, Catholic Relief Service, Organization of American States, and the Costa Rican, Danish, Dutch, Swedish and U.S. governments.
In 1990 Costa Rica advanced a cooperative National Strategy for Conservation and Sustainable Development (ECODES), which is dealing with such broad issues as land-capability assessment and integrated land-use processes, and developing new laws and regulations for the environment, forestry and SINAC. Recently a new law on biodiversity (including wild flora and fauna) was enacted. Funding sought from the Global Environment Facility (GEF) would strengthen the efforts such as BOSCOSA and INBio for the region. Such broad and integrated activities are critical for the survival and healthy functioning of adequately large natural systems of flora and fauna. Top