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Conservation in Southern Costa Rica |
Conservation |
With over 25% of the country set aside to preserve wildlife & rainforest Costa Rica has lots to see. This humid region, in the pacific southwest, comprises some of the largest stands of rainforest in central America.
To contribute to a needed conservation effort contact any of the foundations, groups or hotels listed below. Find out about volunteering a few days of your vacation. Opportunities range from collecting turtle eggs, to feeding monkeys and baby sloths to planting trees. You can also work in local villages and help fix up schools and live with Costa Rican families. |
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Alien Invasion: Exotics, Non-Natives & Invasives |
The first ones were garbage eaters. They lived near the bottom of the shallow water feeding on bits of organic debris, rotting pieces of dead plants and animals. They were the scavengers of the muddy bottom. At some point in time one was born with a difference in its mouth parts; its teeth were a little flatter. There were so many others competing for the rotten debris that the new one often went hungry, until one day, driven by hunger pangs, it ate something new - living algae. It thrived on the new source of nutrients, as did its young. There came a time when the water rose adding new nooks, crannies and rocks to its habitat. Then again one appeared with altered mouth parts; this time it was larger lips. The lips weren’t the best for eating algae and besides there was less algae in the water now. One day it saw a small ripple in the surface and reflexively snapped at the movement, grasping an insect that fell there. With time it got better at catching live insects, and it grew and reproduced. Over many generations the lips grew even thicker, eyes grew sharper and the body longer and slimmer allowing for quick movement. These were the insect catching and eating specialists.
Back near the bottom, one of its ancestors bore an offspring with upturned mouth and large, hard rounded teeth. It learned to feed on snails. Later its offspring and their offspring learned to feed on other shelled animals. Selective pressures assured that the best fitted to find and crush the shelled prey were the most likely to survive and reproduce. At the same time, one of the fat-lipped insect eaters with slightly sharper teeth began to eat the young of the others. And even later another learned to catch and eat the larger plant eaters. Only the individuals best suited for acquiring and consuming their special type of food survived and reproduced. The others either branched off and found a new specialty or perished never to pass on their genes.
This simplified tale illustrates how over thousands of years, as the waters of the lake rose, more specialized niches developed, and with each new habitat and each new source of food one of the cichlids “learned” how to occupy the space and eat the nutrient source. Over 200,000 years elapsed until one day in 1858 an explorer named John Hanning Speke became the first European to behold the giant lake. Being a loyal British subject Speke named Lake Victoria in honor of the queen. At that time it was nearly twice as big as Costa Rica, with a shoreline that would stretch half way around the earth. But the most amazing thing about the lake was the 500 different species of cichlid fish that filled it from top to bottom and shore to shore, utilizing every way imaginable to make a living in that enormous body of water. Almost all of them evolved from a single ancestral species.
Then one day some European sport fishermen decided that the lake needed a good game fish. It was no fun to catch all the “trash fish” that the locals fished for food. So they released a non-native species called the Nile perch, a real sport fish, into Lake Victoria. Now they had a fish that was fun to catch, a real fighter that could reach the length of a tall man and twice the weight. A voracious eater, the perch ate its way through the cichlids like a hungry young boy in a cookie jar. In half a century the Nile perch has eaten over 200 species of Lake Victoria cichlids into extinction. The algae eaters were some of the first to disappear, and possibly none of them are left. Lake Victoria became choked with algae which consumes much of the oxygen, leaving less for the fish and causing many to die. The rotting plant material accumulated and the decomposition process took even more oxygen and soon the bottom feeders died too. Later the shallow portions of the lake became choked with water hyacinth, another non-native species, this one from the Amazon. The thick mats of broad pads of this invasive species are so dense that local fishermen can’t force their boats through them. Malaria carrying mosquitos breed in them as does a snail that carries a terrible parasite called Bilharzia. Three million people who live around the lake have been deprived of their livelihood, and it all began with the introduction of the Nile perch. Lake Victoria has been called the worst ecological disaster of our time.
According to World Book Encyclopedia: “Invasive species are animals, plants and other living things that spread rapidly in new environments where there are few or no natural controls on their growth.” When a given species remains in the habitat where it evolved over many millennia, there are many other species that have evolved together with it. Some of them prey on it, some of them compete with it for food or space, and some of them will parasitize it or make it ill. In turn, each of those species have others that keep them in check. When a species is removed from its native environment and placed in a strange habitat within its preferred range of temperature, humidity and altitude, there are often few, if any, other species that can keep it under control. That’s when the problems begin.
We are all familiar with invasive species, even though we may not know it. If you live in the United States, you are certainly familiar with European starlings, the black birds that clutter up many public parks; kudzu, a broad leafed vine that chokes out native vegetation and takes over vast areas; purple loosestrife, zebra mussels, Dutch elm disease or West Nile fever. If you’re from Australia you know about European rabbits or the Madagascar rubber vine. If you’re British you know may know about the flatworms from New Zealand that are rapidly consuming all of the country’s earthworms, so important for building and enhancing the soil.
In the example of the Nile perch in Lake Victoria, the invasive species caused major ecological damage by preying directly on native species to the point of driving many to extinction. The kudzu vine out competes native species and crowds them out of their space. The European rabbits in Australia multiplied rapidly and consumed pasture that humans need for sheep production. Some invasives bring diseases - like the mosquitos that carry malaria and yellow fever, or the rats whose fleas carry bubonic plague. Still others interbreed with native species altering them genetically. An example of this latter would be the so called “killer bees” that accidentally got established in Brazil and worked their way north arriving in the southern United States about a decade later. They interbred with local honey bees everywhere they went to the point that none of the original pure bloodlines were left.
Often when a non-native species arrives at a new location, it will alter one thing in the environment and that, in turn, will alter other aspects of the environment in a domino effect. In his excellent book on the subject, Life Out of Bounds, Chris Bright recounts the story of the opossum shrimp in the Flathead River in Montana:
/!Wildlife officials introduced the shrimp around 1970 to increase the forage base for the kokanee salmon, another introduced species. But salmon tend to feed near the surface and the shrimp only rose to the surface at night, when the salmon could not see them. So the salmon could not eat the shrimp, but the shrimp ate all the plankton that the salmon fry depended on. The salmon population crashed, then the bears, birds of prey, and other creatures that had come to depend on the salmon disappeared. A tiny shrimp had starved eagles out of the sky.!/
To my knowledge we haven’t had any disasters resulting from bioinvasions in Costa Rica, though we do have some non-native species that have the potential to cause problems. We have thousands of hectares of melina plantations that were planted for paper pulp. A number of imported pasture grasses tend to take over and are extremely difficult to get rid of. One in particular, “German grass,” tends to cover wetlands and form thick mats that soak up all the water and crowd out water birds. However, I’ve noticed that where there is a large native forest nearby, these grasses eventually tend to choke themselves out and, with time, native trees will repopulate the area. In the tropics there are many more species and a lot more competition than in temperate climates, which makes it more difficult for exotics to become established. This large variety of species is called biodiversity, and it is the key to a healthy environment. That doesn’t mean the tropics are safe, by any means. Lake Victoria sits on the equator. It does mean that we need to seriously protect our biodiversity.
The Costa Rican environmental ministry, MINAE, with the enthusiastic assistance of many environmental organizations, has elaborated a strategy for the conservation of the biodiversity of Costa Rica. Additionally, there is a plan for each conservation area within the country. You can find these on internet at www.minae.go.cr/estrategia. Protecting our biodiversity is the best thing we can do to defend ourselves against invasive species. Altered habitats are more vulnerable than intact ones. We need to conserve our tropical forests.
We have a multitude of beautiful native plants in Costa Rica, some flowering, some useful and others merely decorative. When you go to a nursery to buy plants for your garden or landscaping your new home, tell them you want species native to Costa Rica. Better yet, buy from local people. Many country people love plants and have elaborate gardens. They often pot and sell some of their more attractive ones. These are usually displayed by placing the potted plants out by the roadside where motorists will see them and stop to browse and hopefully purchase some. That way you will not only be protecting biodiversity, you will also be helping the local people.
Just because Costa Rica hasn’t experienced a disaster on the scale of Lake Victoria doesn’t mean we don’t have to be on guard. There are some critters out there that could really wreak havoc here. Let’s have a little fun and invent our own nightmare - an animal that, if introduced into Costa Rica, could upset the entire country, not just ecologically, but economically and socially as well. Something that would strike terror into the hearts of everyone, drive away the tourists, destroy fauna and leave the country in a shambles. What characteristics would this imaginary demon have?
First of all, it must be small enough to stow away on a ship or plane without detection and hardy enough to survive a long journey without food. Since one is not enough to invade a country, reproduce and establish a population capable of becoming a threat, more than one should be able to travel on the same vessel or they should be adept enough to stow away many different times. Let’s say it is very sneaky, not easily detected and has a knack for slipping into homes, hotel rooms, offices and just about anywhere it wants to go. Since people are terrified of poisonous animals let’s make it poisonous enough to kill people, especially smaller children and pets. It won’t have any natural predators and will tend to prey on some of our most treasured wildlife.
So what do you think? Does our fantasy animal sound terrifying enough? I hate to tell you this, but this thing isn’t imaginary; it really exists. The brown tree snake, a native of Asia, was introduced into Guam during World War II. It is not known exactly how it arrived on Guam, but it probably came in a cargo ship’s hold. What is known is that they have driven 12 of Guam’s 14 bird species to extinction, destroyed the tourist industry and created paranoia in other Pacific islands, especially Hawaii, where several of them have been discovered in the wheel wells of jet planes. The brown tree snake is poisonous enough to kill a child and has a nasty habit of sneaking into dwellings and small spaces. They are excellent climbers and their long slender bodies can reach 3 meters in length. This species has another trait that makes it the nightmare invader. After a female mates, possibly with several different males, she carries the sperm within her body and may not fertilize the ova and bear young until six months to a year later; and she can have several sets of offspring from one mating. So, conceivably one impregnated female, stowed away in a ship’s cargo hold and off loaded with the cargo would be sufficient to populate Costa Rica. One of them was once found inside a new washing machine that was manufactured in Korea, off loaded in Guam, loaded on another boat and shipped to Houston, where it was discovered.
The worst incident I have ever heard of was a brown tree snake that found its way into a septic tank, probably through the ventilation tube. It crawled up the tube that discharges waste from the toilet into the septic tank, and, you guessed it, bit someone who was sitting on the toilet. I know not where it bit them. Sound scary enough? Chances are the brown tree snake won’t make it to Costa Rica, but it’s possible and there are plenty of other scary things out there as well. Be careful with exotics. Stick with natives. Let’s protect our biodiversity.
For more reading on this subject, I recommend Life out of Bounds by Chris Bright. It is available from www.worldwatch.com.
Article courtesy of Jack Ewing
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