David Waltner-Toews 1

1 Department of Population Medicine and Network for Ecosystem Sustainability and Health, University of Guelph. Guelph, Ontario, Canada N1G 2W1

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I am grateful to the respondents for their critiques both of the arguments I have made, and of the less-than-clear way in which I presented them. They have been generous in making allowances for my own struggle with understanding and presenting the theory and the practice of an ecosystem approach to health. I have tried to incorporate the editorial comments into the article itself in such a way as to clarify my arguments but not, in the interests of real debate, to change them.

I feel the need to clarify the context of the article and make a few general comments. I was invited to take the ecosystem approach to health and apply it to how we think about tropical and emerging diseases. I have elsewhere discussed concepts and models of health in some detail, and in this article focused only on the tension between health - which I describe as a negotiated construct within biophysical constraints - and disease, which is merely one of many constraints (Waltner-Toews & Wall, 1997; Waltner-Toews, 2000). Secondly, the ecosystem approach to health, which is a participatory research and management methodology, firmly rooted in complex systems theories (which include elements of chaos and catastrophe theory), needs to be distinguished from ecosystem health, which is an attempt to apply health management ideas to ecosystems. Whereas the ecosystem approach states that "there is not one material system to which our definitions must conform", ecosystem health tends to take a more biomedical view that there is indeed one material system on which we can agree, and whose health we can assess. Thus ecosystem health tends to focus on outcomes, and the ecosystem approach tends to focus on process. This is obviously not a clear division, rather a difference of focus.

Luiz Jacintho da Silva is quite correct in citing the historical antecedents of viewing diseases in ecological context. What distinguishes Hippocrates, the 19th-century sanitarians, Pavlovsky, and Virchow from this current effort is a changed understanding of the natural world and our place in it. We have gone from a purely empirical sense of inter-relatedness, to miasma theories, to a focus on specific etiologic agents, back to the agent-host-environment triad, and now to a more complex and sophisticated understanding of inter-relatedness. From both da Silva's and Foller's comments, it is clear that I have not communicated with sufficient clarity that the ecosystem approach, because it requires local participation to define the elements and relationships of interest in a given ecosystem, is necessarily rooted in culture as well as nature. However, as Cristina de Albuquerque Possas points out, there are tensions between the scientific tendency to homogenize, and the cultural tendency to particularize. The ecosystem approach, drawing on what has been called Post Normal Science (Funtowicz & Ravetz, 1994), incorporates these tensions by requiring negotiation and what James Kay has called "cross talk" (Kay et al., 1999). Because of this, implementing "ecosystem approach to health" programs must face not only deficits in our understanding of socio-ecological systems, but very real and often daunting political power struggles. We continue to debate these issues, and how to deal with them, in workshops sponsored by the Network for Ecosystem Sustainability and Health (NESH), as well as on our web-site (

Given the practical issues of competing interests, governance, and uncertainties not just among disciplines, but among researchers and non-researchers, both Foller and Moran wonder about implementing this approach. They are quite correct to see these as challenges, but I think Moran is unduly pessimistic. Conflict resolution in the development context has received considerable attention in recent years (see, for instance, Buckles, 1999). Furthermore, we have found, at least at the local community level, that many people understand, accept, and can work with uncertainty and compromise if they are part of the investigative and management process. Many government institutions have problems implementing policies on public health and environmental issues because they assume that their "experts" can adequately define the risks and hence impose solutions on the public. The public will shoulder risks they have chosen, but not those imposed. In this context, the major practical constraints to implementing this approach relate to democracy, a sense of a common good beyond the individual household, and knowledge (not necessarily formal education, but the ability to articulate understanding and argument). In many poor countries, the third component is missing. In North America, a lack of the second component has proven to be the major problem. Again, there are exceptions; some of us have found modern students of science in North America to be unable to clearly articulate understandings and arguments. I did not discuss specific methodological tools in the article, but the process invariably involves triangulating results from a combination of methods, ranging from those developed by participatory action practitioners (which are usually central), to those used in conventional scholarly inquiry, Soft Systems Methodology (Checkland & Scholes, 1991), influence diagrams, and newer dynamic simulation models and Geographic Information Systems. The specific tools used are determined by the questions being asked by the participants.

José Maria G. de Almeida Jr. raises several interesting and important points. Since my wife is a counselor-therapist, I am well aware of EMDR (which links mind and body at an individual level), as well as the broader literature linking mental and social conditions to biophysical health at more encompassing systemic levels in the socio-ecological holarchies (e.g. Evans et al., 1994). Health in the tropics has both socioeconomic (e.g., poverty) and ecological (e.g., climate) constraints. One of the ways we have dealt with that in implementing the ecosystem approach is to require local, public participation defining the research questions and the management options. The process itself empowers people and promotes health; this is what I mean by saying that the means achieve the ends.

I consider gene therapy to be a medical procedure and not a health promotion technique, and cloning faces the same problems as other genetic engineering of organisms, in that (among other things) it changes the rate of change at a particular scale (the individual) and hence creates serious disturbances at other, co-evolving scales which cannot adapt as quickly (Giampietro, 1994). Bill Reese makes this point much more forcefully in his comments. If I have downplayed the rapidity of change and the potential for catastrophe it is because, from a practical point of view, I have found that such descriptions of the situation, while probably true, tend to foster some combination of panic with despair, numbness, or totalitarianism. Indeed, I would argue that many of the lists of quantitative indicators of sustainability generated by international agencies reflect these tendencies. Faced with the urgency of systemic breakdown and hemorrhaging of species, my veterinary training tells me that calm, considered interventions may get us further toward our goals.

Still, Dubos' "mirage of health" can be discouraging for anyone working in the health field, since it quite clearly demonstrates that health, as a state, is a moving, probably unattainable, target. Studies using the ecosystem approach may be classified in static form (Figure 1), and portions of it may be teased apart and made to appear linear (Figure 2), but the process overall is always, in practice, an iterative one of continuous re-negotiation of goals defined from different perspectives, actions, assessments, changed understandings, and re-negotiation (Figure 3). This is not a process with a beginning and an end, and reflects the fact that good health is a function of both the outcomes and how they are achieved. Health in this context is not so much a mirage as a sense of well-being that we need to continually redefine and renew as the world changes.

Dr. Lima Barreto's comments raise the question of whether the ecosystem approach, as here defined, is science at all. John Robinson, Director of the Sustainable Development Research Institute at the University of British Columbia, has argued that what we are talking about is "co-generation of knowledge", and that by referring to it as a kind of "post-normal science" we are giving unwarranted credit to scientists (personal communication). People like Funtowicz and Ravetz tend to see this as an enrichment or expansion in the nature of science, in which the primary task of scientists is to help us find ways to live with what appears to be irreducible uncertainty. That is, in addressing questions marked by epistemological and ethical conflicts and where the stakes and uncertainties are high, a new kind of public science, responding to an expanded peer group, is required. This is still, I think they would argue, a systematic gathering of knowledge in the pursuit of general laws, open to scrutiny and evaluation and verification by peers, and thus qualifies as a kind of science. One could argue that this is simply a sort of "rational politics", a politics informed by science. Barreto's response to this is that political interventions are only partly rational and scientific. As, I would add, is the very notion of health. Indeed, one member of our NESH group - not coincidentally, I think, a Peruvian - has argued that we pay far too little attention to the forces of political economy in our ecosystem approach. Surveying the political and health landscape at the beginning of the 21st century, I have no convincing response to this. The struggle to find reasonable resolutions to complex and often tragically absurd situations is a struggle, I think, worth pursuing.

Barreto wonders how we can measure success. The ecosystem approach is focused on resolving the practical, complex problems of how we can live well (with health), as one species among many, on this planet. In a constantly changing context, how can we know if we have succeeded? In at least one of our projects (in Kenya) we derived two sets of indicators for measuring success - one created by the research team, and one created primarily by the villagers. The latter, we found, were the more useful - though much more difficult for researchers to measure - because they reflected the qualities of life that people actually cared about. Nevertheless, health is also a concept full of contradictions, in which for instance, global health may dictate restrictions on local health, and population health in a context of ecological constraints requires the death of some individuals. Indeed, we face many tragedies which have no technical solutions. As both a scientist and an activist, I think that the ecosystem approach to health, as defined in this paper, which struggles as much with process as with outcome, offers (at least to the extent to which the ideal is realized) some hope for dealing with questions where conventional science and politics appear to be at an impasse. Nevertheless, I do not believe that we will ever find a definitive way of coping with the uncertainty, tragedy, and wonder of the human condition. For this reason, music, poetry, stories, and rituals will always be essential for achieving health. But that is another paper.



BUCKLES, D., 1999. Conflict and Collaboration in Natural Resource Management. Ottawa/Washington, D.C.: IDRC/World Bank Institute.


See the original article for all other references.

Escola Nacional de Saúde Pública Sergio Arouca, Fundação Oswaldo Cruz Rio de Janeiro - RJ - Brazil