A recent trip to three countries in Central America gave me a new appreciation for the impact this rather small piece of land has had on the evolution of life and human history of this planet. Comprised of six countries (Guatemala, Belize, Honduras, El Salvador, Costa Rica and Panama), Central America is an elongated isthmus, which connects the two major American continents.
This wasn't always the case. For a significant part of the earth's history, North and South America were separate and distinct continents on which the forces of evolution resulted in the development of very different flora and fauna.
About two hundred million years ago most of the land mass of the planet formed a single large super-continent known as Pangaea. Through the movement of tectonic plates, this supercontinent divided into two pieces, one of which later fragmented into North America, Asia and Europe while the second, called Gondwanaland, drifted away and eventually separated into South America, Africa, southern Asia, Australia and the Antarctic.
A mere three million years ago, the movement of tectonic plates between North and South America pushed up a mountainous ridge of volcanoes and created, first, a series of islands and, finally, a continuous connection between the two American continents. The appearance of the isthmus of Central America also severed the link between the Pacific and Atlantic Oceans and resulted in the establishment of the Gulf Stream which sweeps warm water up from the tropics across the Atlantic Ocean and brings a moderate climate to Northern Europe.
The closure of an oceanic connection between the Atlantic and Pacific oceans also created an impetus for the divergent evolution of a variety of marine species along each of the Pacific and Caribbean coasts.
The creation of a connection between the two Americas allowed for a great interchange of terrestrial species which probably helps to account for the remarkable biodiversity found in Central America today. With only 0.5% of the Earth's land base, it supports 7% of all the species which inhabit the planet.
This interchange initially included a number of species which later became extinct, including giant ground sloths (originally from South America, they reached Alaska) as well as dire wolves, saber-toothed tigers and primitive horses from North America. These relatively recent extinctions are thought to be due to the arrival, first in North America and then in South America, of a new and efficient hunter - humans - over the land bridge from Asia.
In general, the invasion of North American terrestrial species into South America was far more successful than the reverse migration. Although the jungles of Central America offered hospitable conditions, only a few South American animals (mainly opossums and porcupines) were able to adapt to the drier climate of temperate North America.
In contrast, several species of North American origin became well-established in South America. These include members of the cat and camel families as well as wolves, foxes, raccoons, deer, peccaries, bears, mice, squirrels, skunks and rabbits. While we tend to associate llamas with Peru and jaguars with the Amazon, the ancestors of these animals migrated from North America; their descendants have been hugely successful in finding suitable habitat in South America.
However, the tropical jungles of Central America provide ideal habitat for a number of species of South American origin including a variety of monkeys, anteaters, capybaras, armadillos and agoutis, poison dart frogs, caimans, vampire bats as well as birds such as toucans and the curassow. Thus, a visit to Central America offers opportunities to enjoy landscapes and animals more commonly associated with South America.
The human history of Central America is also fascinating. Guatemala, in particular, remains the heartland of the Mayans who established a major civilization in the northern reaches of Central America from approximately 2000 BC until their decline (thought to be due to extreme drought) around 900 AD. While the heat and humidity of the jungle have destroyed many traces of their civilization, the stonework and statuary of their great cities persists in places such as Tikal, Caracol, Copan, and dozens of other sites.
Elaine Golds is a Port Moody environmentalist who is vice-president of Burke Mountain Naturalists, chair of the Colony Farm Park Association and past president of the PoMo Ecological Society.
