04-13-2006 13:56

Human history is filled with episodes of war. Simple, basic weapons were used in early wars and later evolved into the high tech long range missiles we see today in modern wars. All wars are bloody, with both sides desperate for victory.

Besides the battles recorded in history books, an on-going invisible war has occurred. In this war, the invaders are not humans. A common plant overlooked by most people, an insect easily trampled to death by human feet, or a microorganism invisible to the naked eye, may become bio invaders, sparking a treacherous battle without gun smoke.

In Mazatlan, Mexico, the tranquil life of its residents was once interrupted by a group of invaders from the south. A primary school was attacked by a swarm of killer bees. More than 40 children were sent to hospital for emergency treatment. Several people were hurt and the residents were in a panic. Firefighters went out every morning to do battle with the bees who were spreading to densely populated areas.

Killer bees look similar to ordinary honeybees, but are much more aggressive. When provoked, they will attack violently. Their stingers will remain in the skin of the victim. Though losing their stinger means death for the bee, a chemical is sent into the air, warning the entire swarm, calling them to launch fiercer attacks. They like to attack areas like the eyes, nostrils, and mouth. More than 800 people have been killed by South American killer bees since the 1960's.

Killer bees are not native to the American continent. They are from Africa.

Only three of the over 300 species of bees in Brazil produce honey and at low yields. Brazilian honey producers introduced 54 queens of the African bees in December 1956. The honey yield was then raised but with disastrous results.

The wild African bees produced a hybrid bee when mating with local bees. This hybrid species was aggressive, well organized, swift, and had lethal stingers. In the absence of natural enemies, they attack animals and humans, even in cities. People are helpless against them.

To increase the honey yield, humans created the nightmare of killer bees. It's not a natural disaster but a man-made calamity.

Actually, most bio invasions are man-made. For example, we introduced water hyacinth for animal feed. But it has grown rapidly in Dianchi Lake, covering 1000 hectares of its water surface and killing off native water plants. More than a hundred million RMB is spent every year to destroy and control water hyacinth.

Economic losses due to bio invasions of foreign species in China amount to 57.4 billion RMB annually, while the US spends 150 billion US dollars annually. Even more frightening, some of the ecological damage is irreversible.

Why are these foreign species so powerful?

Every relatively closed space on earth has developed its own ecological balance during long periods of evolution. For example, in South America, large quantities of water hyacinth are eaten by weevils. In the Amazon River, red piranha is the prey of many fish there. Destructive foreign species are docile in their native habitats. Our mistake is that we didn't introduce their natural enemies at the same time.

Foreign species destroy local environments quickly. Humans are forced to wage a war against them. On the Seychelles Islands, a war on mice is occurring. They came to this secluded island by ship 200 years ago. They eat plant seeds, birds and their eggs. Without natural enemies, the mice reproduced at an astronomical rate and threatened all native species. The government is dropping poisonous bait from helicopters to destroy them.

Mice are cunning. The adults won't eat new food without watching the younger ones eat it first. They have to use bait that will trick the mice.

To avoid killing native species, they caught local animals and fed them in cages for six months. The extermination plan was successful. But not all battles are successful. As a Chinese saying goes, "it's easy to invite evil gods but hard to send them away".

This is a family of fire ants, with a population of 250,000; each one has a red stinger.

Like mice, fire ants also traveled in ships to America from Africa. But poison won't work on these red devils like it did on the mice.

These lamp cases had just been checked 3 weeks ago. Now people have to spray pesticides again, especially on electric wires. These ants like electricity more than they fear pesticides.

They eat all electric devices en masse, bringing disastrous consequences.

Every year, the US government spends 2 billion US dollars to fight off the ants, with only slight improvements.

The researchers are forced to try new strategies by introducing a new bio species.

These decapitating flies are enemies of the fire ants, introduced from South America. After mating, they attack fire ants, by laying an egg in the body of the ant.

The egg hatches into a maggot, and moves to the head of the ant. After eating the head, it grows into a fly, and becomes the next generation of ant killer.

This method is risky, because after the fire ants are wiped out, the flies may attack other species and become another bio invader.

This is not paranoia but what once happened in Australia.

The number of rabbits in Australia increased rapidly and unchecked. Measures to prevent them from destroying other living species ended in vain.

Someone introduced foxes to combat the rabbits. However, they ate not only rabbits, but also other small animals. Australians then had to ignore the rabbits and kill the foxes instead.

Once a bio invasion has occurred, the destruction of local ecology usually can't be prevented in a short period.

Ecological balance is gained by a biological chain. A missing link will bring tragic results to a delicate ecological environment. Less than 20 percent of existing species have been studied. Based on such limited knowledge, introducing new bio species is highly risky.


Editor:Wang Ping