Costa Rica’s rich biodiversity is being heralded around the globe in our current age of growing environmental consciousness. This country’s commitment to the protection and restoration of nature has been recognized through a number of awards given for its role as a green leader, such as the Earthshot Prize in 2021, or as the best Wildlife and Nature Destination in 2019.

It is estimated that some 4% of the total world biodiversity can be found in Costa Rica (some have suggested 6%), even though the country represents only 0.1% of the land surface of the planet. Below is a brief geological history of this tiny landmass and how it came to be the rich, natural wonderland that we know and love today.

A Geological History Of Costa Rica

Around 15 million years ago, Central America was a series of islands between the Atlantic and Pacific Oceans that were situated closer to the North American mainland than to South America. The Talamanca Mountain Range was an independent island made of volcanic rocks lying in the seaway between North and South America. Sea currents carried water from the Atlantic between the islands directly into the Pacific Ocean and the deepest passage was the furthest south, through what is now Panama.

Scientists believe that the coastal features that recur frequently along the Pacific Coast (rocky outcroppings, point formations, and large peninsulas) were formed perhaps thousands of kilometers to the southwest as separate islands that were slowly carried to their present-day positions through plate tectonics.

Approximately three million years ago, there were still only three major seaways between the islands. As the seafloor slowly lifted, the islands became large and amalgamated. Although narrow, the land that is now Costa Rica eventually rose from the sea to become a continuous landmass that completely separated the Atlantic Basin from the Pacific at equatorial latitudes. Central America now joined the two vast continental landmasses as a land bridge, which had many environmental effects on the two ancient continents and this newly formed landmass.

Before the completion of the land bridge of Central America, South America had been isolated for tens of millions of years as a true island continent, much like Australia. Isolated evolution over millions of years resulted in the development of many types of animals not seen elsewhere, such as armadillos, giant armadillos, opossums, sloths, giant sloths, and certain giant birds, like the aptly named Terror Birds, which disappeared due to increased predator competition arriving from the north.

Life reconstruction of the terror bird Andalgalornis by John Conway

The great migration of plants and animals from one continent to the other began to occur around 2.7 million years ago. The double migration is known as the great faunal interchange and it permanently altered the composition of animal communities on both continents. Climates were drier in Central America at the time so forest areas were less widespread. Grasslands and savannahs (as exist in Guanacaste today) were more common and grazing animals therefore migrated first. The bones of horses, llamas, elephants, bears, and peccaries, all of which originated in North America, are found in Argentina, with their ancestors having migrated at one point through Costa Rica.

Many animals, such as the elephant and camel, have long been extinct in the Americas since the faunal interchange. They made the crossing but were outcompeted by native species and perished. Other species that started in one continent survive today only on the other, of which the llama is an example.

Costa Rica’s Tropical Evolution

As climates grew wetter, rainforests expanded from the Amazon Basin into Central America. This brought a second major biological interchange, mainly of forest species. Animals, such as monkeys from the Amazon, moved north as far north as Veracruz in Mexico into the moist tropical parts of Central and North America. This later invasion from the South replaced the earlier Central American fauna, which was originally made up of temperate, dry-land species from North America, such as coyotes and white-tailed deer, which remain dominant in the Guanacaste region (the white-tailed deer is the national animal of Costa Rica).

Costa Rica’s national animal, the white-tailed deer

Today, Costa Rica’s fauna and flora are mostly equatorial and Amazonian in nature. Evergreen forests spread into Costa Rica from the Amazon Basin and became Central America’s rainforests. Mountain-adapted organisms from the south also migrated to this area, bringing species from the equatorial Andes Mountains to the Talamanca range – the highest in all of South America.

Biodiversity In Costa Rica Today

Some three million years have elapsed since the invasions from the North and South – long enough for speciation to take place in numerous plants and animals. Unique species found nowhere else on the planet have evolved in several identifiable areas of Costa Rica since then. Core areas with clusters of species restricted to a particular area are known as areas of endemism. Seven such areas exist in Costa Rica, which is a greater number than in any other region of comparable size on Earth.

Areas of endemism are of special interest to biologists because they have been cut off sufficiently from their species in surrounding areas to have begun to differentiate from their neighbors. On a smaller scale, mountains and volcanos are very important isolators because they separate populations on either side. Species of dung beetles and snakes related to one another have begun to genetically diverge on either side of the Talamanca Range, for instance.

Furthermore, environments on the tops of mountains can be vastly different from one another, cut off from their neighbors on the next mountain by the warmer, drier country at lower altitudes. This is even noticeable in our tiny Costa Ballena region where hilltops in the Dominical area have different species of flora and fauna than in Uvita or Ojochal. White-tailed deer, for instance, are typically only spotted in this region in the Lagunas hills, north of Dominical, where the coastal elevation 

Central America’s highest mountain peak, Cerro Chirripo, in Costa Rica’s Talamanca Mountain Range

The Talamanca Mountains of Costa Rica are a major source of endemic species, with numerous insects, birds, and plants – notably bromeliads – different from those anywhere else in the world. 

The Osa Peninsula, too, is a forest derived from tropical antecedents but it has species found nowhere else. Its beetle community is so different that scientists have concluded that Osa was separated from the mainland for a very long time.

Many of us move to Costa Rica to live more closely with this immense biodiversity and we invite you to visit and experience it for yourself. Get in touch with our team when you fall in love and are ready to make the move more permanent.

Subscribe to our weekly newsletter

Subscribe to our weekly newsletter

*Much of the information sourced in this article is paraphrased from a publication by NASA called ‘To The Stars: Costa Rica in NASA