©1997 Blackwell Science, Inc.

VIEWPOINT

.

Bridging the Gap between Humanand Ecological Health

Early threats to human health and well-being came

from

the environment—vector-carried diseases,predators, famine, combat. As human populationsgrew and developed agriculture, permanent set-tlements were established and new threats arose.Contagious diseases moved from domesticatedpets and livestock to humans. Sixty-five humandiseases are thought to have originated from cat-tle (e.g., smallpox, measles, TB); 65 came fromdogs; 42, including influenza, from pigs; and one,the common cold, from horses (Ponting 1991).

Diseases spread more quickly in the crowdedconditions of villages, towns, and cities; inade-quate sanitation was also a problem. These move-ments continue today as demonstrated by Lymedisease, Ebola fever, and, just this year, a new strainof influenza struck humans, transferred from pigsin the Far East.

The industrial revolution brought relief fromsome of these threats; wastewater treatment, forexample, reduced the threat of waterborne dis-eases. But new technologies generate new threats,ranging from toxic industrial chemicals to globaltransportation systems that speed the spread ofinfectious diseases and expose individuals to agreater variety of diseases. Still today, the healthchallenges we face are changing constantly.

Technological advances have in many re-spects improved health care but that technologyalso is a double-edged sword. Widespread use andabuse of antibiotics, for example, stimulates anti-biotic resistance, demonstrating that the threatsthemselves evolve. And the array of threats changesas well. Society needs new health care strategies todeal with evolution on so many fronts.

The papers in this issue came from a specialplenary session of the 1996 meeting of the In-ternational Society for Environmental Epidemiol-ogy (Edmonton, Alberta, Canada). The session’stheme—“Ecosystem Health: Bridging the Gap” —acknowledged that human health is no longerchallenged solely by familiar contagious diseasesor the spread of toxic chemicals.

Rather, modern affluence has brought threats

to

the wider environment—ecological disruptionat scales unprecedented in Earth’s history—whichthreaten equally the well-being of human society.In the long term, perhaps the most importantfrontier of health challenges involves the deple-tion of a natural bounty once thought infinite.Epidemiology must consider ecological health,the condition of ecosytems critical to the successof human society.

Anthony J. McMichael demonstrates the im-portance of a growing awareness of the ecologicaldimensions of population health. Humans havealways influenced their environment, in no smallmeasure the reason for our success as a species.But the scale of human impacts has changed therules. Humans can no longer overlook the funda-mental importance of the biosphere as an infra-structure that sustains human society, nor can wetake that infrastructure for granted. The shift inemphasis from the health of individuals (a localfocus) to regional and even global considerationsrequires creative new solutions with spatial andtemporal dimensions unheard of in the history ofthe public health sciences.

Jack R. Vallentyne reinforces this messagewith analysis of the effects of persistent toxic sub-stances on that infrastructure and on humans inthe region of the Laurentian Great Lakes ofNorth America. Reproductive and developmentalhealth problems associated with persistent toxicsubstances in fish, reptiles, birds, mammals, and,by implication, humans stimulated recommenda-tions by the International Joint Commission onthe Great Lakes (IJC) to halt use of industrialchlorine to protect human and biospheric health.

Yasmin E.R. von Schirnding of World HealthOrganization focuses on the health challengesfaced by humans in cities throughout the world.Age-old hazards are still prevalent and new threatsare emerging. If the public health sciences are toconfront successfully those challenges, she con-cludes, they must seek more integrated, local ap-proaches to protect city dwellers. These approachesmust also recognize the role of cities in environ-

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Ecosystem Health Vol. 3 No. 4 December 1997

mental degradation both in and outside of the ur-ban growth boundary. They must understand andminimize the “ecological footprint” of the city(Wackernagel & Rees 1996). If urban residentsare not in tune with their broad health needs, theprobability of success will be small. In short,healthy and sustainable cities depend on both hu-man health and ecological health. Success is un-likely unless society adopts a broader frameworkof health than has dominated during the past fewcenturies.

All three papers emphasize perhaps the mostimportant health challenge frontier—the deple-tion of a natural bounty once thought infinite,the systematic reduction in the Earth’s ability tosupport life, a phenomenon termed “biotic im-poverishment” by ecologist George Woodwell(1990). Human society can no longer behave as ifthere were no ecological risks or assume that wecan repair and replace the lost and broken partsof ecological systems after we recognize their im-portance to society (Karr 1995).

Biotic impoverishment is visible today inthree major forms: indirect depletion of living sys-tems through degradation of the chemical andphysical environment; direct depletion of nonhu-man living systems; and direct depletion of livingsystems (Karr & Chu 1995). Each is multidimen-sional.

(1) Indirect depletion of living systems: soil depletionand degradation; degradation of water supplies;alteration of global biogeochemical cycles; chem-ical contamination of air, water, and land; and glo-bal climate change and ozone depletion.

(2) Direct depletion of nonhuman living systems: re-newable-resource depletion; extinction of species;habitat destruction and fragmentation; red tides;pest outbreaks; homogenization of crops; spreadof alien species; and epidemics and emerging dis-eases.

(3) Direct depletion of human systems: epidemics;emerging and reemerging diseases; reduced hu-man cultural diversity; reduced quality of life andeconomic deprivation; failure to thrive in infantsand children; and environmental injustice and rac-ism.

The list includes many health hazards that havechallenged human society for millennia. But italso includes many that are not considered ashealth challenges in the conventional sense de-spite their direct and indirect relevance to thehealth or well-being of human society. Collec-

tively, this broad sweep of issues illustrates themagnitude of human and ecological challenges.More important perhaps, it reminds us of theclose association and common underpinning ofecological, social, and public health concerns.

The final paper published here paints insharp relief a danger of cavalier construction ofbridges connecting these three dimensions ofhealth concerns. Trevor Hancock, a health pro-motion consultant, cautions against the simplisticapplication of the methods of medicine to theprotection of ecological health. He first contraststhe medical model with its emphasis on curingacute infections and traumatic conditions withthe public health approach in which protectingand promoting health are the primary goals. Onedeals with problems after they arise; the other ispreventive. He concludes that the preventive orpublic health model is more appropriate to eco-logical health.

He also calls for efforts to avoid actions thathave unanticipated or unintended consequences.Anyone familiar with ecological systems and natu-ral resource management is well aware of thisphenomenon. The use of pesticides to kill croppests, the use of exotic species to control other ex-otic species (mongoose to control rats on is-lands), or the use of hatchery fish to supplementsalmon populations all brought unexpected ef-fects. In each case, the “cure” caused unantici-pated problems (“illnesses”), often with seriousconsequences for desirable commodities or re-gional life-support systems.

Physicians are very familiar with this phenom-enon—iatrogenic (doctor-caused) disease. Thesediseases, caused inadvertently by a physician ormodern medicine in a broader sense, may be clin-ical (infections contracted during an operation),social (dominance of the care of illness by doc-tors), or cultural (coping systems to deal withbirth or death, illness, or suffering have beenusurped by medicine). Because these challengesare so important in human medicine, Hancockcautions against the widespread adoption of amedical model to protect ecological health. Hismessage is important to all concerned about soci-etal well-being, whether they come from medi-cine, epidemiology, or the ecological health arena.

Efforts to bridge the gap between human andecological health require new cooperation andcollaboration among members of the (human)health community (medicine, epidemiology, pub-lic health) and the ecological health community.That collaboration must also recognize the im-

Karr: Ecological Health is Public Health

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portance of improved communication with all cit-izens. We must be more effective at communicat-ing human and ecological health challenges andthe risks associated with those challenges to citi-zens and policymakers so that all concerned com-munities can contribute to policy-making that ad-dresses societal well-being. We must be moremindful of the ecological equivalent of clinical,social, and cultural iatrogenic disease. If we fail toaccomplish that simple task, the unintended eco-logical consequences of efforts to protect humanand ecological health will be a significant share ofthe evolving health challenges faced by humansociety.

Long-term protection of living systems re-quires that we focus on organisms themselves.The health of individual organisms, including butnot limited to humans, and the communities theybelong to provide the most effective markers ofecological health and the most relevant guide-posts for programs to protect society’s economicand ecological interests.

Unfortunately, agencies charged with envi-ronmental protection (protection of ecologicalhealth) are mired in implementing regulationsand overlapping and sometimes conflicting mis-sions and jurisdictions. They emphasize counts ofpermits written or the cataloging of environmen-tal impact statements. They struggle to avoid list-ing endangered species rather than taking actionsto prevent species from reaching endangered sta-tus. Instead of seeking out and treating the rootcauses of present risks to human and ecological

health and preventing their continuation, agen-cies too often assume that chemical or physicalsurrogates and technological remedies will keepthose systems alive. They are wrong. How can so-ciety expect a landscape that can no longer sup-port life to support healthy humans or human af-fairs?

James R. Karr

Professor of Fisheries, Zoology, EnvironmentalHealth, Civil Engineering, and Public Affairs,University of Washington, Box 357980, Seattle,WA 98195-7980.

REFERENCES

Karr, J.R. (1995) Risk assessment: We need more thanan ecological veneer.

Human and Ecological Risk As-sessment

1,

436–442.Karr, J.R. & Chu, E.W. (1995) Ecological integrity: Re-

claiming lost connections. In: Westra, L. & Lem-ons, J. (eds)

Perspectives on Ecological Integrity

; pp.34–48. Kluwer Academic Publishers, Boston, MA.

Ponting, C. (1991)

A Green History of the World: The Envi-ronment and the Collapse of Great Civilizations

. St.Martin’s Press, New York.

Wackernagel, M. & Rees, W. (1996)

Our Ecological Foot-print: Reducing Human Impact on Earth

. New SocietyPublishers, Philadelphia, PA.

Woodwell, G.M. (ed) (1990)

The Earth in Transition: Pat-terns and Process of Biotic Impoverishment

. CambridgeUniversity Press, Cambridge, UK.