On the fate of frogs, bats and rose bushes

Stuff happens – and stuff happens in the garden. But, these are things that can’t be talked about with neighbors who notice my mail box tilts drunkenly or remark that the new people across the street should mow their lawn more frequently, especially now that it’s getting warmer. Walking alone in my garden with coffee cup in hand, the night dew still slickening the leaves, I pause at a new plant at another struggling to survive. I notice fungus on my rose bushes and fret about the future of mankind.

It's the weekend. I can think about whatever I want. Right?

OK. So I’m told that, not tomorrow or the next day, but in the future, say sixty-five million years from now, we many not be here. I peer at the roses, the fungus exhaling millions of spores as I stand mute in my ignorance and bathrobe, and wonder if this is the beginning of the end, wonder if this is proof that we’re all doomed. The world is ending, not in a cataclysm, but in the stealthy creep of pathogens.

I’m not alone in this concern, as dramatic as it sounds. Writer Elizabeth Kolbert did a story about a year ago in The New Yorker about the possibility of a Sixth Global Extinction.
Read more: www.newyorker.com/reporting/2009/05/25/090525fa_fact_kolbert#ixzz0o5x4wqzy.

What I got from the article is that pathogens, specifically, fungi are attacking various life forms and killing them – frogs, bats and California oak trees.

Scientists say that of the numerous species that have existed on earth, more than 99 percent have disappeared. But, extinction, which is seen as bad and preventable, causes a lot of argument and finger pointing. Today, there are many expensive and naive efforts under way to prevent it. I worry that these attempts are futile, even silly. Are we homo sapiens merely putting our fingers in the evolutionary dike and pretending we can make a difference in the history of the universe? Is global warming the single cause of our demise?

Throughout the 18th century, the prevailing view was that species were fixed. Charles Darwin believed extinction happened slowly, but he was wrong. In Kolbert’s article, she noted that researchers have found that during the past half billion years, there have been at least 20 mass extinctions. Five of these—the so-called Big Five—were so devastating that they’re usually put in their own category.

The fifth, the end-Cretaceous event, which occurred 65 million years ago, exterminated not just the dinosaurs but 75 percent of all species on earth. Once a mass extinction occurs, it takes millions of years for life to recover, and when it does it’s generally with a new cast of characters.

In this way, mass extinctions have played a determining role in evolution’s course. It’s hard to say when the current extinction event—sometimes called the sixth extinction— began. Scientists speculate that its opening phase started about fifty thousand years ago, when the first humans migrated across Australia and America.

If current trends continue, by the end of this century as many as half of earth’s species will be gone. For example, researchers first noticed something odd was happening to amphibians. The main culprit in the wavelike series of amphibian crashes it turns out is a chytrid fungus, known as Bd. At this point, Bd appears to be unstoppable.

In 2007, biologist Al Hicks, of the New York State D.E.C., and the National Wildlife Health Center started investigating a series of mysterious bat deaths. Many of the dead bats were discovered with a white substance on their nose, which was cultured and found to be an unidentified fungus. In California, millions of native oak trees have died from the fungus-like Phytophthora ramorum, a photo of how destructive it can be is show here.

One of the maddening puzzles of mass extinction is why, at certain junctures, the resourcefulness of life seems to falter. Just in the last century, carbon dioxide levels in the atmosphere have changed by as much as they normally do in a hundred-thousand-year glacial cycle. In the end, the most deadly aspect of human activity may simply be the pace of change itself, moving too fast for life as we know it to change.

Today, fungi account for 30 percent of emerging infectious diseases in plants. These fungal diseases can radically alter natural ecosystems as well as food and agricultural production. A report in Science Daily last week noted that examples include chestnut blight fungus, which eliminated nearly 100 percent of native chestnut trees throughout eastern American forests during the last century, and, more recently, the Phytophthora cinnamomi fungus that’s threatening native forests throughout Australia.

And, other fungal pathogens have been responsible for the epidemic leading to the Irish potato famine in the 1840s and, more recently, the stem rust disease of wheat, first identified in Uganda in 1998 and now threatening North Africa, the Middle East and Asia.

So what is the Sixth Extinction? When is it coming? And what is its cause?

"It's the next annihilation of vast numbers of species and it is happening now, and we, the human race, are its cause," explains Dr. Richard Leakey, the world's most famous paleoanthropologist and co-author of the 1995 book The Sixth Extinction: Patterns of Life and the Future of Humankind. He says every year between 17,000 and 100,000 species vanish from our planet.

"For the sake of argument, let's assume the number is 50,000 a year,” Leakey says. “Whatever way you look at it, we're destroying the Earth at a rate comparable with the impact of a giant asteroid slamming into the planet, or even a shower of vast heavenly bodies."

The statistics he has assembled are staggering. Fifty per cent of the Earth's species will have vanished inside the next 100 years; mankind is using almost half the energy available to sustain life on the planet, and this figure will only grow as our population leaps from 5.7 billion to 10 billion inside the next half-century. Such a dramatic and overwhelming mass extinction threatens the entire complex fabric of life on Earth, Leakey said, including the species responsible for it: Homo sapiens, that all life as we know it is destined to vanish.

Like I said, I worry and I wonder, study the underside of leaves in my garden. All this talk about the nature of pathogens is raising startling new questions in my peanut brain. I wonder about the role of fundamental scientific research and how the study of evolution plays into our understanding of emerging disease.

In particular, I’m concerned about how specific, new species occur when a subset of a population shifts to a new host, like fungus attacking frogs, bats and oak trees. It gets on a new organism and adapts, killing the host, moving on. I slurp the last of my coffee and contemplate powdery mildew on my pumpkin leaves, decide it’s time to head for WalMart and the garden chemical section. I cannot save the planet or its amazing diversity of species. I can, however, treat fungus in my own backyard.