The Area de Conservación Guanacaste (inscribed in 1999), was extended with the addition of a 15,000 ha private property, St Elena. It contains important natural habitats for the conservation of biological diversity, including the best dry forest habitats from Central America to northern
and key habitats for endangered or rare plant and animal species. The site demonstrates significant ecological processes in both its terrestrial and marine-coastal environments. Mexico
Guanacaste is located in north-western
. It stretches 105 km from the Pacific, across the Pacific coastal lowlands, over three tall volcanoes and down into the Atlantic coastal lowlands. It includes the Guanacaste Cordillera and surrounding flatlands and coastal areas. The most notable volcano is Rincon de la Vieja, which has three craters and one lagoon. Its last eruption was observed in the 1970s, but some fumarole activity still occurs in one of the craters. At the base of the volcano are several minor craters. Costa Rica
At least 32 rivers and 16 intermittent streams originate in the vicinity of the volcano, and flow into the Tempisque, a river of enormous importance for irrigation of agricultural land in the
. The marine area includes various near shore islands and islets (mostly uninhabited), open ocean marine zones, beaches, rocky coasts, and approximately 20 km of sea turtle nesting beaches and a high diversity of wetland ecosystems (37 wetlands). The wetland forests are considered to be among the most pristine in Guanacaste Province Central America and worldwide.
On the Naranjo and Nancite beaches during the breeding and mating season (August to December), over 250,000 turtles nest. The majority of them are olive ridley turtles. The green, leatherback and hawksbill turtles also use the beaches quite extensively.
Guanacaste's beaches are of global importance for the protection of Olive ridley sea turtles and leatherback sea turtles, both endangered.
The main vegetation types include mixed deciduous forest with fig trees and rosewood; evergreen gallery forests along streams and behind the occasionally flooded zone; savannahs with exotic jaragua grass; oak forests and savannahs; and mangroves. There is also beach vegetation, and areas of calabash forest. The intact altitudinal transect contained within the site protects an entire elevational and east-west seasonal migratory route from the Pacific coast to 2,000 m above sea level, from dry forest to cloud forest and down to Atlantic rainforest, which is critical for the range and life histories of many species of animal.
In the area of Volcan Rincon de la Vieja, four different forest types are present: tropical wet; premontane moist; premontane rain; and lower montane rain; this forest is covered by clouds all year and the trees are dwarfed because of prevailing strong winds and sandy soils.
The area contains a very diverse fauna with several species of conservation concern. Some notable mammals are white-tailed deer, white-lipped peccary, collared peccary, Central American tapir, white-face monkey and spider monkey, howler monkey, collared anteater, jaguar, margay, jaguarundi and ocelot.
The avifauna is well represented in the area with more 500 species. Among the bird species the following are the most common: military macaw, rufescent tinamu, spot-bellied bobwhite, great curassow, crested guan, blue-winged teal, roseate spoonbill, thick knee, jabiru, ibis and laughing falcon.