Ecological Risk and Surprise on the GMO Roller Coaster

by Ed Grumbine
Winter 2002

Next time you're dangling from a rope in the middle of a Yosemite big wall, ripping downhill on a bike headed into a logging road hairpin or zipping shut your tent in occupied hyena habitat deep in the African bush, take a moment to ponder all the ways you get yourself going too high, too fast and too far out for your own good.

We all take risks and manage them as best we can. Consider climbing rope: When it becomes visibly frayed, you replace it. Few people tackle Moab's bike trails knowing that their brake pads are as smooth as slickrock. And I do not go to sleep in the bush wearing the Baggies that I drenched with anchovy oil during dinner. Risk is part of the fabric of life. We can learn to deny, avoid and reduce risk, but we can never eliminate surprise. We all know this now – post-September 11, 2001 – more than we ever did before. Yet while humans will always struggle to live with uncertainty, surprise is one of nature's ways of running the world. Unpredictability and nature's creative power are what yield biodiversity – the bewildering array of tropical orchids, the mysterious arc of monarch butterfly migration and the habits of bears all trace back to the endless recombination of the genetic building blocks of life.

We don't run the world. But with the creation of transgenic, or genetically modified organisms (GMOs), we are acting as if we do. And because we think we are running the world, we have never thought through what risk really means as we splice our way into Earth's genetic pool. Like a climber on a 5.10 pitch with a thunderstorm approaching who discounts the behavior of lightning, if we don't gauge the risk of GMOs we can never judge well whether we should proceed or retreat.

Some would argue that with GMOs the decision to proceed has already been made. In 1996, four million acres of GMO crops were planted worldwide. In 1999, that figure had increased to 87 million acres. So far, few negative consequences to biodiversity have occurred and despite the hype, few benefits have accrued. Yields (and profits) have increased modestly and herbicide use has decreased about one percent.

But risk should not be measured in hindsight.

Both mountaineers and scientists gauge future risk against conditions in the here and now. A climber observes peaks and weather, ponders "what if?" and makes decisions. Using this same approach, when biologists measure what is known about transgenic plants, three kinds of ecological "what ifs?" come into focus.

The first risk is that GMO plants will survive, reproduce and sustain themselves outside of cultivation. This could lead to herbicide – and insecticide – resistant superweeds that could become highly invasive. Experiments done to evaluate this risk suggest that it will happen occasionally. The consequences are unknown.

A second risk is that GMOs will eventually hybridize with close wild relatives. When hybrids survive and reproduce in the wild, the spread or introduction of transgenes into wild gene pools will occur, creating new invasive species. This risk is not farfetched. Seven of the world's 13 major crop plants, simply through traditional breeding practices, have mixed their genes with closely related wild species to form new weeds. This has eliminated the genetic uniqueness of some wild plants and contributed to extinctions. One thing is clear, the potential for genetic mischief increases with total area of cultivation.

Both self-sustaining GMO plants and transgenic hybrids could add to the worldwide list of biological invaders. After habitat degradation, most scientists consider invasive species to be the most dire threat to biodiversity. Over 50,000 plants are not native to North America. In my California county about one of every three plants in the wild is from someplace else. Exotics that out-compete native species cost $137 billion a year to control in the United States alone. GMOs will only add to this burden.

The third risk is the potential of transgenic plants to impact nontarget species and ecosystems. Say you plant a Roundup-tolerant GMO plant. With this wonder, you can spray your field and keep it clear of weeds while your transgenic crop thrives. But indirectly, there will be fewer seeds and insects for wild birds to eat. Multiply this by X millions of acres and watch what happens to food supplies for birds and small mammals. And nobody is watching. There are only a handful of experimental studies based on models and no long-term studies of any kind.

It is precisely because we are not running the world that the potential for a wide variety of negative, indirect ecological effects from GMO plants is great. You may have read recently about how monarch butterfly larvae were killed because the milkweed leaves they ingested were dusted with pollen from transgenic corn fitted out with the genes of Bacillus thuringiensis (Bt), a natural insecticide. There is experimental evidence that GMO crops reduce soil decomposition rates and alter soil carbon and nitrogen levels. There is precious little data to evaluate the risks associated with these known ecosystem responses to transgenics. The same can be said of potential risks associated with virus-resistant GMO crops and forest supertrees.

Assessing the ecological risks of GMOs is, in the end, much more complex than the judgment calls that outdoors people make every day. If you fall off a rock face, that may be your final climb, but monarch butterflies will most likely survive. If a grizz mistakes me for a school of anchovies, I may not hike again, but soil microbes will continue to consume the dead and the down in the Cornbelt. The scale of risk associated with GMOs is not personal, but global. Transgenic risks are ecological and endlessly variable, not up close and personal like a boulder or a bear.

With GMOs, the chips are down. Even with more experiments, field trials and better data, we cannot measure every ecological variable in a field of cotton, let alone a forest. Genes exist in the world to flow, and we are helping them move around in unprecedented ways.

There is only one sensible path to follow. We must place an immediate moratorium on introducing GMOs and use this interlude to clearly measure the risks of transgenics against the status quo, chemical-intensive agribusiness as well as the sustainable future offered by organic farming. Maybe we can grow enough food more efficiently and at a reduced ecological cost by releasing lady beetles instead of planting Monsanto Bt corn. No one really knows because no careful comparisons have ever been attempted.

We are rearranging the world because there are profits to be made and because dominant values are skewed toward power and control. There are other values alive in the world. In conservation science, we study nature and marvel at elegance and surprise. Organic growers ask the land not "how much?" but "how well over time?" In Zen, the teachers say "minimize harm."

Clip into your climbing harness, fasten your toe clips, cinch up your pack's hip belt, and remember why you are here.

À propos de l'auteur

Ed Grumbine grows non-GMO crops in a small garden in the hills outside of Santa Cruz, California. He directs the Sierra Institute undergraduate wilderness program through UC Santa Cruz Extension ( and has published extensively on biodiversity and wildness.