By Donella Meadows
–May 14, 1998–
We of the industrial culture pretty much accept the laws of physics. We don’t waste time trying to make perpetual motion machines. We don’t expect water to run uphill or gravity to go away. These concessions to reality don’t stop progress, they just keep us, most of the time, from dead ends and disasters.
If only we’d develop the same respect for the laws of ecology.
Ignoring an ecological law has produced a problem summarized with some alarm in the May 7 issue of the New England Journal of Medicine. The bacterium called salmonella infects several million Americans a year. Most of us just get a stomach upset, but salmonella can kill the very young, very old, or immune-compromised, unless it is knocked out by antibiotics. The problem is that a type of salmonella, called DT104, has become resistant to five common antibiotics — ampicillin, chloramphenicol, streptomycin, sulfonamides and tetracycline.
In 1980 antibiotic-resistant DT104 showed up in less than one percent of samples tested at the Centers for Disease Control. Now it shows up in 34 percent. It is even more widespread in England, where some strains show resistance to six or seven antibiotics.
Why? Many doctors and scientists, including an expert committee of the World Health Organization, assume it’s because we slosh around antibiotics carelessly, especially in animal feed. Raising cattle, chickens, and hogs by the thousands in tight confinement invites the spread of infection. So antibiotics are routinely mixed into animal feed. Forty percent of U.S. antibiotic sales go to this purpose.
The ecological law being violated here is natural selection. Expose salmonella to an occasional medicinal dose of antibiotic, and you’ll kill them. Expose them every day to a slight dose, you’ll kill some. The ones that survive will be the most naturally resistant. They will produce the next generation, which will be even more resistant. Keep using sublethal doses of antibiotic, and you’ll end up with resistant bacteria. It’s about as predictable as water flowing downhill.
People who understand natural selection have been trying to stop routine feeding of antibiotics for years. European nations ban it, except for the U.K. The New England Journal article says, “In the United Kingdom DT104 now appears to be widely distributed in food animals, particularly cattle, and investigations have associated infections in humans with eating pork sausages, chicken, and meat paste and with contact with sick animals. Investigations in the United States have found associations between DT104 infections in humans and the consumption of unpasteurized dairy products and direct contact with livestock.”
Not to worry, say some technological optimists. We can invent new antibiotics. But evolutionary races with tiny, fast-breeding, stunningly adaptable creatures such as bacteria and insects are about as winnable as perpetual motion machine contests. Pesticide companies should have learned that lesson long ago. Spraying the countryside with bug poison, like feeding animals antibiotics, is just asking for resistant bugs. More than 500 pest species have developed pesticide resistance.
But we don’t seem to learn. A new round of ignorance about natural selection is about to destroy not only one of humanity’s best insect-control practices, but one of nature’s too.
A bacterium called Bacillus thuringiensis — Bt for short — normally hangs out in soil and on leaves waiting for a bug to eat it. Different strains of Bt infect different bugs, including cabbage worms, corn earworms, and Colorado potato beetles. In the bug’s gut the Bt multiplies happily, makes a toxin that kills the bug, and releases millions of offspring to go infect other bugs. Organic gardeners use Bt as a natural insect control. It poisons nothing but the insect that is its host. Insects have not evolved Bt resistance, because they’re not exposed to Bt toxin until the Bt is inside them, by which time they’re goners.
Along comes Monsanto, snips out the bacterial gene that codes for the Bt toxin. pastes it into the genes of potatoes, corn, cotton. The genetically engineered seeds command a high price, because every cell of the plant makes pesticide. When a potato beetle or cotton bollworm chomps a leaf, it ingests Bt toxin.
If you see this as a perfect scheme for creating resistant pests, you understand the law of natural selection. Instead of occasional exposure to Bt toxin, the pest encounters it throughout the growing season. Inside of a lethal dose, it gets a low-level one — Bt-spliced cotton kills only 60 to 90 percent of cotton bollworms. The ones that survive breed the next generation.
No one knows what will happen in nature if insect populations become resistant to wild Bt. Organic farmers are incensed that an ecology-deaf company is going to wipe out one of their most effective natural controls. You’d think Monsanto itself would be worried, because Bt resistance will undo its own gene-spliced products. For awhile their scientists and executives pretended to have a “resistance management plan,” which most farmers and entomologists saw as unworkable. Now Monsanto spokespeople are admitting that resistance is probable, but, says Erich Sachs, business director for Yield-Gard, Monsanto’s Bt-resistant corn, “Resistance is unlikely to happen within five years, and within that time frame we’ll offer new technology that will further reduce the likelihood of resistance.”
Trust us. We’ll have a perpetual motion machine any time now. So we can go ahead and destroy all these other machines that work just fine.
Copyright Sustainability Institute 1998