 A GORP Content Partner Adapted from Costa Rica; The Last Country the Gods Made by Adrian Colesberry |
Change & Profusion |
Before Costa Rica became part of the permanent landbridge from North to South America, its uplifted portions formed an island archipelago between the two continents.
Ecologically, these islands resembled the Caribbean islands at Western contact: they were dominated by seed plants from the south and animals from the north, such as raccoons, that could island-hop. Surprisingly, tree sloths from South America had managed to populate the temporary islands also. Later, when the Central American isthmus formed in the middle of the Ice Age, northern animals dominated, and species from South America, such as the opossum, the armadillo, and the porcupine, migrated as well.
Plants moved across the newly formed land bridge, too. Alpine plants moved from the North American Rocky Mountains to the higher altitudes of what would become Costa Rica. Mountainous plants from the Peruvian Andes spread to the north as well, but reached only as far north as the Talamancan range in southern Costa Rica. Eventually, tropical forest and the animals that lived in it—monkeys, capybaras (the world's largest rodents), agoutis (Guinea pigs), and anteaters from South America—moved in, replacing the island grasslands and putting finishing touches on an ecosystem that would see no significant changes until Spanish contact.
The Costa Rican tropical forest's famous genetic diversity derives from an abundance of food and consistently moderate weather, which reduces to near zero the natural pressures placed on forest inhabitants. Without environmental stress, species evolve by adapting different defenses against perdition and by developing various means of competing with other organisms for favored resources and shelter. An animal under great environmental pressure evolves in less complex ways than does a creature of the tropics.
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A Canadian caribou, for instance, adapts to sub-zero weather simply, by growing a thick, bushy coat. In contrast, tropical butterflies evolve in countless ways to avoid being eaten by birds. These insects may eat a plant that makes their flesh distasteful, develop a coloring pattern that confuses predators, fly only at night to avoid most birds, fly in a self-protective flock, leave the female in a safe, semi-larval stage throughout her reproductive cycle, resemble a common leaf, resemble a distasteful butterfly, or merely reproduce in such great numbers that predators cannot eat every one. In as many ways, tropical plants generate methods to compete for incoming light. Lush jungle life means prolific numbers of species.
In such forest, the slightest shift in pattern can result in yet another species. For example, a species of bee that pollinates a certain nocturnal orchid only visits the flower between 12 AM and 3 AM; all orchids not in bloom between those times cannot be pollinated, and, thus, cannot propagate. Yet on one occasion, three orchids bloom accidentally at dawn and miss their bee pollinator. In most cases, such flowers would die without producing offspring. But, by chance, these few orchids get visited by a hummingbird that has the right beak shape to pollinate them, and they bear fruit. If this offbeat pollination occurs faithfully for a few generations, this particular type of orchid will never again bloom in time for bees, but a new orchid species pollinated by hummingbirds will have begun.
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- To Make a National Park
- House Made of Rain
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