Science and Environmental Health Network - Home Page
 about sehn   contact us   links  
 
P r e c a u t i o n a r y  P r i n c i p l e 

Precautionary Principle - Essays

The Precautionary Principle And Then What? Attending to the Context of our Innovations (1)
Frederick Kirschenmann
If we were to grasp the true nature of nature---if we could comprehend the real meaning of evolution---then we would envision a world in which every living plant, insect, and animal species is changing at every instant, in response to every other living plant, insect, and animal. Whole populations of organisms are rising and falling, shifting and changing. This restless and perpetual change, as inexorable and unstoppable as the waves and tides, implies a world in which all human actions necessarily have uncertain effects. The total system we call the biosphere is so complicated that we cannot know in advance the consequences of anything that we do.
- Michael Crichton
In the domain of emergence, the assumption is made that both actual systems as well as models operate by selection from immense space and variability of the world of the possible, and in carrying out this selection, new and unanticipated properties emerge . . .. emergence leads to novelties . . .

. . . nature yields at every level novel structures and behaviors selected from the huge domain of the possible by pruning, which extracts the actual from the possible. The pruning rules are the least understood aspect of this approach to emergence, and understanding them will be a major feature of the science of the future.
- Harold J. Morowitz
. . . we hardly give any thought to the long-range consequences of our scientific and technological interventions into man's life and nature.
- Rene Dubos
A few months ago David Hurd, former CEO of the Principal Financial Group, told an audience that, as the head of his company, he had learned to insist on an important procedure. Whenever anyone in his company suggested any kind of innovation, he had learned to ask, seven times, "And then what?" This simple exercise, he contended, saved his company from many unintended negative consequences that might otherwise have caused the company significant harm.

From a pragmatic perspective, Mr. Hurd's caution is simply an appeal to common sense. We should try to foresee as many of the unanticipated consequences of our actions as possible before we engage in them. However, Mr. Hurd's pragmatic management strategy also is consistent with recent scientific insights which force us to recognize that the world we live in is more complex and dynamic - and therefore much less predictable - than we previously thought.

The New Science of Caution
Hurd's strategy also corresponds with recent observations by physicists who suggest that if we took both Laws of Thermodynamics seriously, we might re-think the way we introduce technologies into the universe.(2)

Based on insights reaching back at least to Descartes, Newton and Galileo, we had come to view the world as a static, mechanical and predictable system. Nature, we assumed, existed in a state of equilibrium and functioned much like a clock. It was believed that we could predict nature, and our interventions in it, with certainty. Consequently, it was believed that human intervention in nature for the sole benefit of the human species was morally mandated. Technological innovation to replace or improve upon natural occurrences came to be regarded as the salvation of the human species.

Today we understand that nature is anything but clock-like. It is a highly dynamic, constantly evolving, living system consisting of very complex sets of relationships. With each stage of the evolutionary process, things become more complex and more dynamic, and emerge with increasing speed. Life first appeared on our planet as single-celled creatures about four billion years ago. It took almost two billion years before nuclei began to appear in cells. It only took a few hundred million years for multi-cellular organisms to emerge. Then things really start to speed up. An explosion of diversity occurred a few hundred million years later. Within a couple of hundred million years of the present day, large plants and complex animals are already on the scene. Hominids evolved from the great apes roughly five or six million years ago. Then a species emerged about 35,000 years ago that was not only artistic, as attested to by cave paintings, but also had developed both the capacity to dramatically change its environment and to rationalize its behavior.(3)

Since we now understand that we live in a very dynamic, emerging world, David Hurd's pragmatic management protocol not only makes good business sense, but also suggests a vital way of living in the world. Asking "and then what?" at least seven times recognizes that we can never introduce any innovation into the dynamic, emerging world in which we live without setting in motion a series of related consequences that are rarely apparent at the time or place of introduction. The future welfare of the human species may therefore hinge on such cautionary action. Asking "and then what?" at least seven times seems especially prudent as we contemplate introducing a new generation of technologies that are self-replicating and easily accessible. Thoughtful scientists are, in fact, now calling for exactly such restraint.(4)

Of Arts and Sciences
Literary artists have, of course, urged such caution for millennia. Ancient as well as modern literatures are replete with warnings about the indiscriminate introduction of new technologies unaccompanied by the exercise of appropriate wisdom. Greek mythology recounts the story of Daedalus, "the cunning one" who fashioned wings out of feathers and wax so that he and his son, Icarus, could escape from the Labyrinth that he himself had constructed for King Minos and within which the king later imprisoned him. Before launching their flight with the newly invented wings, Daedalus warned his son Icarus to fly "the middle way"---not too high lest the heat of the sun melt the wax in his wings, but not too low lest the tides of the sea catch him. Daedalus flew the middle way and escaped to safety, but Icarus became intoxicated with his new power, flew too near the sun and plunged to his death. The lesson seems clear. New technology can be very useful, even to save us from previous technologies, but if we fail to exercise appropriate caution it can destroy us.

The ancient Hebrews were even more explicit in their warnings. The Garden of Eden story in the book of Genesis portrays a bit of Hebrew mythology which makes it clear that if Man and Woman do not live in creation on creation's terms if they succumb to the temptation of arrogantly assuming that they know better (the Tree of Knowledge) than the ecology of nature (the Tree of Life) how the garden should be managed—then they will experience one curse after another and eventually find themselves expelled from creation's fecundity.

Many similar literary examples are familiar to us. The tale of the sorcerer and the servant who misuses his master's magic has been told in many forms. Johann Wolfgang von Goethe captured the story in a powerful poem entitled "The Magician's Assistant" in the late eighteenth century. In the late twentieth century, Nancy Willard used the same tale to create a poem for children entitled "The Sorcerer's Apprentice".(5) The tale, in each case, depicts a wise magician who has the power to make dramatic changes in his environment. The servant or apprentice, ignorant of the judicious use of the powers, releases them indiscriminately only to find unintended consequences replicating themselves until they are totally out of control and cause great destruction. The lesson, as Nancy Willard suggests, is that masters learn by their failures and discover that unnatural changes must be undertaken with care---"a single lapse in common sense can have a fatal consequence." In her nineteenth century novel, Frankenstein, Mary Shelley spins a similar cautionary tale.

Contemporary novelists are carrying on this tradition. In Jurassic Park, and in his most recent novel, Prey, Michael Crichton urges us to exercise caution in the introduction of new technologies.(6) Some critics have attempted to diminish the import of Crichton's concerns because his imagination trumps his science (7) or because some of his fictional accounts won't be feasible for at least another hundred years (or maybe it's 25 years?).(8) But surely no one dismisses the significance of the Daedalus story because human flight with wings of wax and feathers is scientifically impossible, or denies the value of "The Sorcerer's Apprentice" because sorcery is scientifically suspect. The use of poetic license as a means to modify human behavior has a long and prestigious tradition.

But we don't have to believe in scary scenarios about futuristic run-away new technologies to learn that we need to use more caution when introducing novelties into the universe. On-the-ground examples of ecological backlash from technologies we have already released into the environment provide ample rationale for adopting Mr. Hurd's precautionary approach to introducing novelties into the universe.

Ecological Failures
In his essay "On the Meaning of Ecological Failures in International Development" (published in a summary of a 1968 conference on the ecological aspects of international development convened by the Center for the Biology of Natural Systems at Washington University), Barry Commoner outlined numerous examples of ecological failures that have resulted from technological innovations we had introduced.(9) Commoner concentrates on the ecological failures reported at the conference by field specialists.

Irrigation projects resulted in dramatic disease outbreaks and geophysical changes resulted in a reduction of agricultural potential. Since irrigation systems increase the amount of standing water near villages and work areas, they also increase the prevalence of life-threatening, waterborne diseases such as malaria. Waterlogging and salinity problems associated with irrigation rendered soil unusable for food production. Similarly, synthetic pesticides introduced to control agricultural pests increased pest problems due to the development of resistant strains of the pest and the reduction of natural predators.

In other words, ecological failures associated with the introduction of novel technologies were already well understood in the late 1950s and early 1960s. Yet we remain reluctant to employ adequate ecological screens to determine whether or not a new technology can be released into the environment without causing ecological harm.

Today we can, of course, readily add many more ecological failures to Commoner's list. The introduction of fossil fuel technologies contributed significantly to global warming. The introduction of chlorofluorocarbons depleted the stratospheric ozone layer exposing life on earth to harmful ultraviolet radiation. The introduction of synthetic chemicals is likely interfering with the reproductive process of many animals as well as the developmental processes of humans, especially children. The introduction of PCBs and DDT decades ago continue to be a threat to the health of numerous organisms. The introduction of nuclear power exposed human societies to many incalculable risks and incurred numerous unanticipated costs.(10) A source of energy thought to be "too cheap to meter" turned out to be too expensive to use.(11) Nuclear energy, in fact, serves as a chilling example of our failure to ask "and then what?" before introducing a technology into the environment. No one even addressed the problem of decommissioning nuclear power plants before they were constructed. "The International Atomic Energy Agency did not hold its first meeting on decommissioning until 1973, almost twenty years after the first reactor was built." (12)

Commoner reminds us that all of the innovations introduced into international communities in the 50's and 60's were thought to be "technological advances" that would spur international development and certainly were not expected to cause harm. But as it turned out "they were in operational fact powerful intrusions on large-scale geophysical and ecological systems," that often ended up causing more harm than good.

Accidents vs. Design Failures
Commoner goes on to assert that these ecological failures were not the result of "random accidents" but were, rather, inherent in the way modern science and technologies are conducted. Commoner suggests that we fail to anticipate many of the unintended consequences of our technological innovations because our sciences have been "dominated by an intensely reductionist approach" and that such an approach is "a poor guide to the understanding of those realms of nature which are stressed by modern technology."

It is such reductionism, Commoner argues, which leads us to believe that "the most fruitful way to understand life is to discover a specific molecular event" rather than to understand the "biology of natural systems." It leads us to explore new ways to use nitrogen but think little about the "fundamental biology of soil nitrogen." It leads us to focus on the immediate properties of a new detergent - "Is it a good washing agent? Is it soft on milady's hands? Will it turn linen whiter than white? Will it sell?" - and neglects to ask, "What happens when it goes down the drain?"

Reductionism, in other words, fails to ask, "And then what?"

The failure of reductionism has, of course, been acknowledged in many fields. Richard Levins and Cynthia Lopez point out that while reductionist science has given us many technologies to attack diseases it has fallen far short of the goal of promoting human health. The reason, they argue, is that "It is at the level of complex interactions that our science has been least successful. Fragmentation of knowledge prevents us from seeing the whole, and reductionist methodologies encourage explanations within the confines of single disciplines, assigning relative weights to 'factors' rather than elucidating their interactions." (13)

Reductionism is, of course, not an evil science. Reducing complex phenomenon into fragments that can be more easily understood is essential to our understanding of how the world works. It is using those bits of information to design solutions to problems, without considering the context of the dynamic, emerging world of which those bits are merely ingredients, that gets us into trouble. It was not the act of reducing atoms to nuclei - which led to the discovery of nuclear fission and nuclear fusion, giving us the knowledge to convert mass into energy - that was problematic. It was our assumption that this knowledge provided a quick easy way to alleviate energy shortages without considering the disorders (the entropy) that the introduction of the technology into the environment would inevitably cause. It is our failure to attend to the context of our innovations, not the potential for innovation produced by reductionist science, which causes, and will continue to cause, unanticipated ecological failures.

It is our continuing failure to evaluate our knowledge of the part in the context of our knowledge of the emerging whole - our failure to anticipate the disorders inherent in entropy as well as the potential inherent in energy - that leads to ecological failures. As Barbara McClintock reminds us, it is this restrictive sense of causality that leads to environmental catastrophes. "We were making assumptions we had no right to make. From the point of view of how the whole thing actually worked, we knew how part of it worked . . . We didn't even inquire, didn't even see how the rest was going on." (14)

I believe that Commoner and McClintock are right. We don't even inquire. It is as if we believed that we could "step out of" our ecological neighborhoods---that we could ignore Mother Nature.(15) We largely ignore the context into which we introduce our innovations. We assume that the way a particular technology works to solve a particular problem---like killing a target pest (the part)---has little to do with the emergent world in which the pest lives (the whole). What is particularly unsettling is that we continue to behave this way as we contemplate introducing a new generation of powerful, self-replicating technologies. We continue to be focused, almost exclusively, on a particular solution that a particular technology might bring to a particular problem and, at best, assume that strict regulatory measures will prevent the technology from producing unintended consequences. The Second Law of Thermodynamics would seriously challenge that assumption.

An Alternative Approach
It is precisely at this point that we should seriously ponder Crichton's central themes. In Jurassic Park he writes, "The history of evolution is that life escapes all barriers, life breaks free, life finds a way . . ." In Prey he warns that "The total system we call the biosphere is so complicated we cannot know in advance the consequences of anything we do," We are not in control (Jurassic Park) and things seldom turn out the way we think (Prey). These are themes worth pondering as we try to decide whether or not it is a good idea to plant pharmaceutical crops in Iowa's cornfields. Whether or not Crichton's imagination trumps his science is beside the point.

The irony of all this is that there is another approach to problem solving that we seldom consider, an approach that promises more sustainable, long-term results. Joe Lewis, pest management specialist with the Agricultural Research Service's Insect Biology and Population Management Research Laboratory in Tifton, Georgia, outlines this new approach with respect to pest management.(16) Lewis argues that we have been trying to solve pest problems in agriculture by introducing technologies to get rid of the pest rather than trying to understand the system failure that allows the pest to emerge. And it hasn't worked! Instead of asking, "How do I get rid of the pest?" he suggests we should be asking, "Why is the pest a pest?" The former question leads us, inevitably, to inventing a direct external counterforce to the problem without understanding what caused the problem to begin with and without considering the disorders the intervention may cause. The latter question is more likely to lead us toward solutions arrived at by understanding and redesigning the system. Lewis sums it up:

. . . application of external corrective actions into a system can be effective only for short-term relief. Long-term, sustainable solutions must be achieved through restructuring the system . . . The foundations for pest management in agricultural systems should be an understanding and shoring up of the full composite of inherent plant defenses, plant mixtures, soil, natural enemies, and other components of the system . . . The use of pesticides and other "treat-the-symptoms" approaches are unsustainable and should be the last rather than the first line of defense. A pest management strategy should always start with the question "Why is the pest a pest?" and should seek to address the underlying weaknesses in ecosystems and/or agronomic practice(s) that have allowed organisms to reach pest status.
Lewis contends that this principle of pest management holds true for molecular biology as well as toxic chemicals.

Fortunately some new approaches to science and technology that subscribe to the principles outlined by Lewis are now being inaugurated. The Green Chemistry movement, for example, takes a fundamentally different approach to reducing potential negative impacts on the environment due to the use of chemicals.(17) The traditional approach had been to minimize risk by limiting exposure - that is by controlling circumstantial factors through regulating the use, handling and disposal of chemicals. As we now know, that approach has largely failed to protect the environment. Green Chemistry attempts to decrease the risk of introducing chemicals into the environment by minimizing hazard - that is by designing or selecting chemicals that are benign. It is one way of taking the "And then what?" question seriously.

Green Chemistry made several other interesting discoveries as a result of studying natural systems. Nature uses very few chemicals to accomplish a host of tasks. By contrast we have tended to use a host of chemicals to accomplish a few tasks. Similarly, while we were attempting to succeed at mechanical engineering, we failed to notice that plants had already gotten organic chemistry down cold.

The Biomimicry movement is another example of solving problems by redesigning the system rather than introducing an external counterforce. Spearheaded by physicist Janine Benyus, the biomimicry movement operates on the principle that nature, by virtue of its long evolutionary journey, has already solved most of the problems we are grappling with. Consequently, biomimicry suggests that we explore nature as a reservoir of solutions to be discovered, rather than a series of defects to be corrected.(18)

Since life on this planet has been around for some four billion years nature has solved a lot of problems by extracting the "actual from the possible". As Harold Morowitz reminds us, "nature yields at every level novel structures and behaviors selected from the huge domain of the possible by pruning.(19) Since nature has done this pruning, solutions to many of the problems we want to solve are already available. Forests might serve as a permaculture-design of edible landscapes using many-storied cropping systems. What potential might that have for designing a more productive agriculture that is less dependent on exogenous inputs and therefore potentially less disruptive to natural systems? Marshes might serve as models for constructing wetlands that function as waste treatment facilities while providing refuges for wildlife. Providing habitat for wildlife might, in turn, provide free ecosystem services to agriculture---more pollinators come to mind. The prairie might serve as a model for perennial cropping systems that are more resilient, ecologically restorative, and economically profitable than current annual mono-cropping systems that hardly mimic nature at all. What are the mechanisms that bats, salmon, homing pigeons and monarch butterflies have developed to navigate as effectively as they do, and how might we mimic them to improve human navigation? The list of possibilities goes on.

These are all ways of redesigning systems to potentially eliminate problems rather than introducing external counter forces into systems in an effort to solve problems. Redesigning systems to mimic nature represents one way, and perhaps the best way, of asking "and then what" before introducing a novel technology.

With respect to agriculture, Wendell Berry counseled such an approach over a decade ago.

. . . an agriculture using nature, including human nature, as its measure would approach the world in the manner of a conversationalist. It would not impose its vision and its demands upon a world that it conceives of as a stockpile of raw material, inert and indifferent to any use that may be made of it. It would not proceed directly or soon to some supposedly ideal state of things. It would proceed directly and soon to serious thought about our condition and our predicament. On all farms, farmers would undertake to know responsibly where they are and to "consult the genius of the place." They would ask what nature would be doing there if no one were farming there. They would ask what nature would permit them to do there, and what they could do there with the least harm to the place and to their natural and human neighbors. And they would ask what nature would help them do there. And after each asking, knowing that nature will respond, they would attend carefully to her response.(20)
The Precautionary Principle
Asking the "And then what?" question before introducing a novel technology is another way of saying that it is "better to be safe than sorry." This way of acting has been adopted by proponents of the Precautionary Principle. The Principle suggests a framework for decision-making that enables us to introduce a technology when the science concerning its potential impact on the environment is uncertain. Essentially the Precautionary Principle suggests that we should act to protect the environment before scientific proof of harm can be established. Green Chemistry and biomimicry are proactive ways of applying the Precautionary Principle. In other words, one way to reduce the uncertainty surrounding the introduction of a technology is through removing the intrinsic hazard by using technologies that have already been selected by nature. One of the positive side effects of this approach is that it reduces or eliminates the need for regulation and the associated costs of regulation.(21) That is perhaps the most productive way of asking the "and then what?" question.

But does that mean we can never use a technology that hasn't been "pruned" by nature? The short answer is that for the foreseeable future we will. Until we conduct more research focused on approaches similar to Green Chemistry and biomimicry we will have to continue introducing some technologies that did not evolve with nature. What benchmarks might we then use in applying the "and then what?" question when we try to select appropriate technologies that will not produce unacceptable, unintended consequences?

A few years ago I wrote an essay wrestling with this question as it related to the introduction of technologies in agriculture. I proposed four principles that could be applied to all technologies.(22)

  1. If the magnitude of potential harm is limited, we might say yes to the technology. If the effect of the introduction of a material or practice could last for generations—if it doesn't disappear in one generation—we should say no.
  2. If the geography of the potential harm from the technology is limited, we might say yes to the technology. The larger the area affected by the introduction of a material or practice, the more safeguards we must use. For example if the technology to be introduced is airborne, waterborne, bio-accumulative, or in other ways ubiquitous to the environment, we should say no.
  3. If the biology of the potential harm is limited, we might say yes to the technology. Since all species in a biotic community have coevolved, we must take the welfare of all species into consideration. If the introduction of a material or practice potentially threatens the integrity or capacity for renewal of the biotic community, we must say no.
  4. If the potential social cost of the technology is limited we might say yes. Often we say yes to the introduction of a material or practice because the short-term economic gain is attractive, or because it has great potential for economic gain for one sector of society. But, rarely are these gains weighed against the long-term economic costs. If the introduction of a technology compromises future economic wellbeing or is achieved in one sector of society at the expense of another sector, we should say no.
Unfortunately in today's industrial climate such precautions are seldom considered, and indeed some sectors of our society are hostile toward them. But as we make our way into what could be a perilous future, we would do well to remember the sage advice that "nature always bats last". At the very least we might ponder Crichton's closing lines in Prey,
They didn't understand what they were doing.
I'm afraid that will be on the tombstone of the human race.
I hope it's not.
We might get lucky.
But then, again, we might not! In any event we might begin asking "and then what?" at least seven times before we proceed much further. And, we should probably all hope that the next stage of emergence on our planet is the emergence of wisdom within the human species!


References
(1). Presented at the Iowa State University's Department of Chemical Engineering 2002-2003 Seminar Series, January 16, 2003.

(2). Jack Hokikian, 2002. The Science of Disorder. Los Angeles: Los Feliz Publishing. The first Law of Thermodynamics stipulates that the amount of energy in the universe is constant---that it can neither be created nor destroyed. The second law stipulates that entropy increases irreversibly in all processes. Hokikian contends that these two laws affect all physical, social, environmental, economic and intellectual processes. He asserts that humanity would be better served, consequently, if we devoted more of our energy to the development of knowledge and attitudes that help us understand the emerging world in which we live, (especially the irreversibility of natural processes) and less on technologies designed to control or reverse that emergence. "Our perspective on the world is very different if we view it as a reversible system subject to our control rather than an irreversible system governed by the Laws of Thermodynamics."

(3). Harold J. Morowitz, 2002. The Emergence of Everything: How the World Became Complex. New York: Oxford University Press. Morowitz traces the emergence of everything through 28 steps, from the "big bang" to "the spiritual"---the spiritual being the "attempt to ascribe meaning to the other emergences."

(4). Bill Joy, co-founder and Chief Scientist of Sun Micro-systems, was one of the first industrial scientists to call for much greater caution in the release of the new generation technologies---genetic engineering, nanotechnology and robotics. See Bill Joy, 2000. "Why the Future Doesn't Need Us," Wired. April.

(5). Nancy Willard, 1993. The Sorcerer's Apprentice. New York: The Blue Sky Press.

(6). Michael Crichton, 2002, Prey, New York: HarperCollins Publishers, is perhaps the most recent call for caution regarding the introduction of nanotechnology, genetic engineering and computer-based artificial life. In his 1990 novel, Jurassic Park (New York: Knopf Books), Crichton urged caution with respect to the release of novel life forms into nature.

(7). Jim Holt, in his review of Prey in the New York Times Book Review (November 24, 2002), says, "The problem with Prey is not that Crichton puts in too much science; it is that the science is of an anything-goes variety that allows him to indulge his tackier imaginative impulses." In a similar vein, in her book The Century of the Gene, Evelyn Fox Keller considers "the utterly fantastic premise that one could clone a dinosaur from its DNA" as Crichton does in Jurassic Park, as an "egregious problem."

(8). In her review of Prey in Business Week, (December 2, 2002), Heather Green quotes inventor Ray Kurzweil who points out that some people predict it will take 100 years before nanotechnologies can be self-replicating but since we are "doubling the paradigm shift for every decade, . . . we'll be there in 25 calendar years."

(9). Barry Commoner, "Summary of the Conference: On the Meaning of Ecological Failures in International Development," in M. Taghi Farvar and John P. Milton (eds.) 1972. The Careless Technology: Ecology and International Development. Garden City, NY: The Natural History Press.

(10). Vezelay Group. 1991. "Global Risks at Stake: From Thought to Action," April. No one anticipated Three Mile Island or Chernobyl, although both were probably foreseeable disasters.

(11). Lester R. Brown, 2001. Eco-Economy. New York: W. W. Norton and Company.

(12). Cynthia Pollock, quoted in Carolyn Raffensperger, "Waste Disposal and Decommissioning," in John Byrne and Steven M. Hoffman, eds., 1996. Governing the Atom. New Brunswick: Transaction Publishers.

(13). Richard Levins and Cynthia Lopez, 1999. "Toward an Ecosocial View of Health," International Journal of Health Services, Vol. 29, No. 2, 261-293.

(14). Quoted in Evelyn Fox Keller, 2000. The Century of the Gene. Cambridge, Massachusetts: Harvard University Press.

(15). Niles Eldredge, 1995. Dominion: Can Nature and Culture Co-Exist? New York: Henry Holt & Co.

(16). W. J. Lewis, et al. 1997. "A Total System Approach to Sustainable Pest Management," Proceedings of the National Academy of Sciences 94: 12243-8.

(17). Martyn Poliakoff, J. Michael Fitzpatrick, Trevor R. Farren, Paul T. Anastas, 2002. "Green Chemistry: Science and Politics of Change," Science, Vol. 297, 2 August. 807-810.

(18). Janine M. Benyus, 1997. Biomimicry. New York: Quill, William Morrow & Co.

(19). Harold J. Morowitz, Op.Cit..

(20). Wendell Berry, 1990. What Are People For? San Francisco: North Point Press.

(21). Poliakoff, et al. Op. Cit.

(22). Frederick Kirschenmann, 1999. "Can We Say "Yes" to Agriculture Using the Precautionary Principle: A Farmer's Perspective," in Carolyn Raffensperger and Joel Tickner, Protecting Public Health and the Environment. Washington DC: Island Press.


Print Friendly Page
 
| SEHN