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Monday, August 10, 2009

Avian Silence: Without Birds to Disperse Seeds, Guam's Forest Is Changing

"The forest on Guam is silent."

"Sometime after World War II the brown tree snake arrived as a stowaway on this U.S. Pacific island territory 6,100 kilometers west of Hawaii. It has since extirpated 10 of the island's 12 native forest bird species. The remaining forest birds have been relegated to small populations on military bases, where the snakes are kept in check. In the first study of its kind, a rugby-playing researcher named Haldre Rogers is documenting how the forest itself is changing."

"There's nothing in the forest on Guam," Rogers says, "and when you hear anything you have to stop and say, 'What was that?'"

Rogers is a doctoral student at the University of Washington in Seattle who once had a cell phone with the number 777-HISS during the three years she worked for the U.S. Geological Survey's brown tree snake rapid response team. From 2002 to 2005, she estimates she nabbed about 100 snakes out of a population estimated in the hundreds of thousands.

"People knew that the birds had disappeared, but nobody had taken the next step to see what impact that had," she explains, "which is why it seemed like enticing research."

"Some 25 percent of U.S. birds are facing extinction, and many common U.S. bird species have declined by 50 to 80 percent since 1967. On islands, the situation is particularly dire, with 28 to 56 percent of species expected to be extinct by 2100, many due to introduced species. Hawaiians are dreading the day when the brown tree snake inevitably establishes itself there, despite careful monitoring of airports and shipping facilities."

"Rogers is now looking for similar trends in a dozen other tree species on Pacific islands, and investigating how the absence of birds has affected populations of agricultural pests and spiders, which are 40 times more abundant on Guam than on neighboring islands. She says it is still too early to know if the brown tree snakes are just altering the distribution of trees in the forest, or if they could lead to a collapse of the island's entire ecosystem."

"The brown tree snake is held up as textbook example of how a destructive invasive species can eradicate birds," she says. "This shows that the effects of introduced predators reverberate through the ecosystem."

Not only are bird species being eradicated on Guam due to the brown snake, the snake is also being blamed for a reduction in the number of tree species found on Guam:

"Before introduction of the brown tree snake, Guam had 12 species of native forest birds. Today 10 of those are extinct on Guam, and the other two species have fewer than 200 individuals. Though Guam has some non-native bird populations, few other birds moved in when native species died out, and none of them live in the forest. That leaves few birds to consume tree seeds and then drop them away from the trees.That could have two possible negative impacts on the native forests, Rogers said. First, some plant species need birds to handle their seeds to ensure effective germination. In addition, seed predators and fungi that kill seeds are often found in high density directly beneath a parent tree, so the trees rely on birds to disperse seeds beyond the range of those negative effects. If native birds performed those functions on Guam, tree populations could suffer from the loss of birds. It appears 60 percent to 70 percent of tree species in the native forests are dispersed, at least in part, by birds, she said."
According to Dr. Gad Perry, "there may be up to 2 million of the serpents on Guam,
 possibly the highest density of brown tree snakes on earth!!!!" How bad is this problem? So bad that
scientists such as Smithsonian pathologist Don Nichols are trying to " find some
 kind of disease that we can release onto the island that is specific for snakes," says Nichols.
 "There [are] two particular strains of virus I'm looking at right now, which, in the laboratory,
cause severe disease and death in these snakes."

To read an in-depth evaluation of the brown tree's snake's role in causing
severe changes within the Guam ecosystem please

Photograph of the brown tree snake taken by :Isaac Chellman

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Thoughts worth thinking about

"Our subconscious minds have no sense of humor, play no jokes and cannot tell the difference between reality and an imagined thought or image. What we continually think about eventually will manifest in our lives."-Sidney Madwed

Laws alone can not secure freedom of expression; in order that every woman and man present their views without penalty, there must be spirit of tolerance in the entire population.- Albert Einstein Too often we underestimate the power of a touch, a smile, a kind word, a listening ear, an honest compliment, or the smallest act of caring, all of which have the potential to turn a life around. - Leo Buscaglia

A person's true wealth is the good he or she does in the world. - Mohammed

Our task must be to free ourselves... by widening our circle of compassion to embrace all living creatures and the whole of nature and its beauty. -Albert Einstein

The best way to find yourself, is to lose yourself in the service of others. - Ghandi

The unselfish effort to bring cheer to others will be the beginning of a happier life for ourselves. - Helen Keller

Aim for success, not perfection. Never give up your right to be wrong, because then you will lose the ability to learn new things and move forward with your life. Remember that fear always lurks behind perfectionism. Confronting your fears and allowing yourself the right to be human can, paradoxically, make yourself a happier and more productive person. - Dr. David M. Burns

Life is as dear to a mute creature as it is to man. Just as one wants happiness and fears pain, just as one wants to live and not die, so do other creatures. -His Holiness The Dalai Lama

Mankind's true moral test, its fundamental test (which lies deeply buried from view), consists of its attitude towards those who are at its mercy: animals. And in this respect mankind has suffered a fundamental debacle, a debacle so fundamental that all others stem from it. -

Milan Kundera, The Unbearable Lightness of Being

The worst sin towards our fellow creatures is not to hate them, but to be indifferent to them. That's the essence of inhumanity. -George Bernard Shaw

Ego's trick is to make us lose sight of our interdependence. That kind of ego-thought gives us a perfect justification to look out only for ourselves. But that is far from the truth. In reality we all depend on each other and we have to help each other. The husband has to help his wife, the wife has to help the husband, the mother has to help her children, and the children are supposed to help the parents too, whether they want to or not.-Gehlek Rinpoche Source: "The Best Buddhist Writing 2005 pg. 165

The hostile attitude of conquering nature ignores the basic interdependence of all things and events---that the world beyond the skin is actually an extension of our own bodies---and will end in destroying the very environment from which we emerge and upon which our whole life depends.