Costa Rica is famous worldwide for its high species and habitat diversity, which is attributed to its geologic history and geographical location. As the volcanoes of the boundary between the Cocos and Caribbean Plates lurched skyward, they formed an island chain between North and South America. For many plants and animals, the lands were close enough to allow a species exchange while still allowing marine organisms from the Pacific Ocean and the Caribbean Sea to interact. About three million years ago, the subduction zone formed a continuous land link, allowing land animals to migrate between the continents, an interaction that is referred to as the Great Continental Interchange.

Ancient armadillos, porcupines and opossums native to South America made their way up to temperate North America, some colonizing Central America en route. Animals such as tree sloths and monkeys, however, never moved north of Mexico. Deer, tapirs, bears, mastodons and cats, like the saber-toothed tiger, migrated into South America, again, some settling in Central America. The result of this sudden exposure of plants and animals to new environments, niches, prey and competitors was a dramatic increase in species diversity. This eventually lowered and leveled off as nature established a new equilibrium.

Some animals became extinct and others thrived. The land rise also resulted in the separation of the oceans, which also may have contributed to speciation through geographical isolation. The volcanoes of Costa Rica are still rapidly (geologically speaking) growing taller, creating new climates and habitats in the process. The land encompasses mangrove swamps, rainforest, montane cloud forest, páramo (sub-alpine grassland) and dry deciduous forest. Because only specially adapted organisms are able to survive at high elevation and in dry climate, the volcanic peaks of the country can be considered ecological “islands” and are crawling with species that do not exist elsewhere. Because Costa Rica lies within the tropics, it receives sunlight directly overhead throughout the year. This fact combined with the unusually high level of rainfall that it receives has resulted in perfect growing conditions for an enormous variety of plants. Throughout most of the country, it is moist enough to allow epiphytes such as orchids to grow. These plants grow on the branches of trees, taking advantage of them only to get closer to the sun and collecting their own nutrients and moisture falling through the air in tight reservoirs. A single tree may support dozens of different species of plants. Animals have evolved to fill the many niches provided by the diverse forests. By feeding on a plant that no other animal feeds on, for example, a species is able to survive by avoiding competition. The consequence of all of these factors – the Great Continental Interchange, tropical latitude, high rainfall and varied topography – has led to an unparalleled biodiversity in Costa Rica. In fact, according to the World Resources Institute, 5% of all known species are native to Costa Rica, giving it a higher biodiversity per unit area than any other country on earth. It has:
• 12 Holdridge Life Zones (biological habitats defined according to their altitude, climate and forest
type) of the 36 in the world
• Over 850 bird species – a tenth of all known species, far more than in North America, Australia or
Europe
• Over 200 mammal species, 27 of which are endangered, including all six cats
• Over 35,000 insect species, including:
• More than 1000 bu