| Imbalance of Ecosystems and Its effect | | | | Asia, Africa, and South America have |
| on Public and Livestock health | | | | originated in coastal areas. Symptoms of |
| Dr.Kedar Karki M.V.St. (Preventive | | | | cholera include explosive watery |
| veterinary Medicine) | | | | diarrhea, vomiting, and abdominal pain. |
| Central Veterinary Laboratory | | | | The most recent pandemic of cholera |
| Tripureshwor | | | | involved more regions than at any |
| The health of humans, like all living | | | | previous time in the twentieth century. |
| organisms, is dependent on an ecosystem | | | | The disease remains endemic in India, |
| that sustains life. Healthy ecosystems | | | | Bangladesh, and Africa. Vibrio cholerae |
| are the sine qua non for healthy | | | | has also been found in the United |
| organisms. Yet there is abundant | | | | States-in the Gulf Coast region of |
| evidence that many life-support systems | | | | Texas, Louisiana, and Florida; the |
| are far from healthy, placing an | | | | Chesapeake Bay area; and the California |
| increased burden on human health. In | | | | coast. |
| some areas of the world, gains in life | | | | The increase in prevalence of V. |
| expectancy and quality of life made | | | | cholerae has been strongly linked to |
| during the twentieth century are at risk | | | | degraded coastal marine environments. |
| of being reversed in the twenty-first | | | | Nutrient-enriched warmer coastal waters, |
| century. The consequences of ecosystem | | | | resulting from a combination of climate |
| degradation to human health are | | | | change and the use of fertilizers, |
| numerous, and include health risks from | | | | provides an ideal environment for |
| unsafe drinking water, polluted air, | | | | reproduction and dissemination of V. |
| climate change, emerging new diseases, | | | | cholerae. Recent outbreaks of cholera in |
| and the resurgence of old diseases owing | | | | Bangladesh, for example, are closely |
| to ecological imbalances. Reversing this | | | | correlated with higher sea surface |
| damage is possible in some cases, but | | | | temperatures. V. cholerae attach to the |
| not in others. Prevention of ecological | | | | surface of both freshwater and marine |
| damage is by far the most efficient | | | | copepods (crustaceans), as well as to |
| strategy. | | | | roots and exposed surfaces of |
| DEFINING ECOSYSTEMS | | | | macrophytes (aquatic plants) such as the |
| An ecological system may be defined as a | | | | water hyacinth, the most abundant |
| community of plants and animals | | | | aquatic plant in Bangladesh. Nutrient |
| interacting with each other and their | | | | enrichment and warmer temperatures give |
| abiotic, or natural, environment. | | | | rise to algae blooms and an abundance of |
| Typically, ecosystems are differentiated | | | | macrophytes. The algae blooms provide |
| on the basis of dominant vegetation, | | | | abundant food for copepods, and the |
| topography, climate, or some other | | | | increasing copepod and macrophyte |
| criteria. Boreal forests, for example, | | | | populations provide V. cholerae with |
| are characterized by the predominance of | | | | habitat. Subsequent dispersal of V. |
| coniferous trees; prairies are | | | | cholerae into estuaries and fresh water |
| characterized by the predominance of | | | | bodies allows contact with humans who |
| grasses; the Arctic tundra is determined | | | | use these waters for drinking and |
| partly by the harsh climatic zone. In | | | | bathing. Global distribution of marine |
| most areas of the world, the human | | | | pathogens such as V. cholerae is further |
| community is an important and often | | | | facilitated by ballast water discharged |
| dominant component of the ecosystem. | | | | from vessels. Ballast water contains a |
| Ecosystems include not only natural | | | | virtual cocktail of pathogens, including |
| areas (e.g., forests, lakes, marine | | | | V. cholerae. |
| coastal systems) but also | | | | Two other examples of how ecological |
| human-constructed systems (e.g., urban | | | | imbalances lead to human health burdens |
| ecosystems, agro-ecosystems, | | | | concern the increased prevalence of Lyme |
| impoundments). Human populations are | | | | disease and hantavirus pulmonary |
| increasingly concentrated in urban | | | | disease. Lyme disease, sonamed because |
| ecosystems, and it is estimated that, by | | | | it was first positively identified in |
| the year 2010, 50 percent of the world's | | | | Lyme, Connecticut, is a crippling |
| population will be living in urban | | | | arthritic-type disease that is |
| areas. | | | | transmitted by spirochete-infected |
| A landscape comprises a mosaic of | | | | Ixodes ticks (deer ticks). Ticks acquire |
| ecosystems, including towns, rivers, | | | | the infection from rodents, and spend |
| lakes, agricultural systems, and so on. | | | | part of their life cycle on deer. Three |
| Precise boundaries between ecosystems | | | | factors have combined to increase the |
| are often difficult to establish. Often | | | | risk to humans of contracting Lyme |
| regions slide into one another | | | | disease, particularly in North America: |
| gradually, over a protracted | | | | (1) the elimination of natural deer |
| "transition" zone, as for example | | | | predators, particularly wolves; (2) |
| between the boreal forest and the Taiga | | | | reforestation of abandoned farmland has |
| regions of Canada. | | | | created more favorable habitat for deer; |
| ECOSYSTEM HEALTH | | | | and (3) the creation of suburban |
| It is important to recognize the | | | | estates, which the deer find ideal |
| inherent difficulties in defining | | | | habitat for browsing. The net result is |
| "health," whether at the level of the | | | | a rising deer population, which |
| individual, population, or ecosystem. | | | | increases the chances of humans coming |
| The concept of health is somewhat of an | | | | into more contact with ticks. |
| enigma, being easier to define in its | | | | By 1995, in the southwestern United |
| absence (sickness) than in its presence. | | | | States, hantavirus infection was |
| Perhaps partially for that reason, | | | | confirmed in ninety-four persons in |
| ecologists have resisted applying the | | | | twenty states, with 48 percent |
| notion of "health" to ecosystems. Yet, | | | | mortality. Variants of the strain that |
| ecosystems can become dysfunctional, | | | | causes hantavirus pulmonary syndrome |
| particularly under chronic stress from | | | | have also been found in other areas of |
| human activity.Example for this can be | | | | the country, as well as in Asia and |
| cited the discharge of nutrients from | | | | Europe. The virus is apparently |
| sewage, industrial waste, or | | | | asymptomatic in rodents, and it is |
| agricultural runoff into lakes or rivers | | | | transmitted in their saliva and excreta. |
| affects the normal functioning of the | | | | In humans it has a flu-like |
| ecosystem, and can result in severe | | | | presentation, which is followed by acute |
| impairment. Excessive nutrient inputs | | | | respiratory distress syndrome. The |
| from human activity was one of the major | | | | primary reservoir in the Four Corners |
| factors that severely compromised the | | | | area of the southwestern United States |
| health of the lower Laurentian Great | | | | is the deer mouse. Climatic |
| Lakes (Lake Erie and Lake Ontario) and | | | | disturbances, which in recent years are |
| regions of the upper Great Lakes (Lake | | | | thought to be exacerbated by human |
| Michigan). Unfortunately, degraded | | | | activity (e.g., global warming), appear |
| ecosystems are becoming more the rule | | | | to set up conditions that trigger |
| than the exception. | | | | outbreaks. In the early 1990s, ENSO |
| The study of the features of degraded | | | | events initially caused drought |
| systems, and comparisons with systems | | | | conditions to develop in the |
| that have not been altered by human | | | | southwestern United States. This led to |
| activity, makes it possible to identify | | | | a decline in plant and animal |
| the characteristics of healthy | | | | populations, including natural predators |
| ecosystems. Healthy ecosystems may be | | | | of the deer mouse. Heavy rains followed |
| characterized not only by the absence of | | | | the drought in 1993, resulting in a |
| signs of pathology, but also by signs of | | | | bumper crop of piñon nuts, a major food |
| health, including measures of vigor | | | | supply for the deer mouse. Subsequently |
| (productivity), organization, and | | | | the deer mouse population greatly |
| resilience. | | | | increased, bringing about increased |
| Vigor can be assessed in terms of the | | | | contact with humans and triggering the |
| metabolism (activity and productivity) | | | | outbreak of hantavirus. |
| of the system. Ecosystems differ greatly | | | | Antibiotic Resistance and Agricultural |
| in their normal ranges of productivity. | | | | Practice Antibiotic resistance is a |
| Estuaries are far more productive than | | | | growing threat to public health. |
| open oceans, and marshes have higher | | | | Antibiotic resistant strains of |
| productivity than deserts. Health is not | | | | Streptococcus pneumoniae, a common |
| evaluated by applying one standard to | | | | bacterial pathogen in humans and a |
| all systems. Organization can be | | | | leading cause of many infections, |
| assessed by the structure of the biotic | | | | including chronic bronchitis, pneumonia, |
| community that forms an ecosystem and by | | | | and meningitis, have greatly increased |
| the nature of the interactions between | | | | in prevalence since the mid-1970s. In |
| the species (both plants and animals). | | | | some regions of the world, up to 70 |
| Invariably, healthy ecosystems have more | | | | percent of bacterial isolates taken from |
| diversity of biota than ecologically | | | | patients proved resistant to penicillin |
| compromised systems. Resilience is the | | | | and other b-lactam antibiotics. The use |
| capacity of an ecosystem to maintain its | | | | of large quantities of antibiotics in |
| structure and functions in the face of | | | | agriculture and aquaculture appears to |
| natural disturbances. Systems with a | | | | have been a key factor in the |
| history of chronic stress are less | | | | development of antibiotic resistance by |
| likely to recover from normal | | | | pathogens in farm animals that |
| perturbations such as drought than those | | | | subsequently may also infect humans. One |
| systems that have been relatively less | | | | of the most serious risks to human |
| stressed. | | | | health from such practices is |
| Healthy ecosystems can also be | | | | vancomycin-resistant enterococci. The |
| characterized in economic, social, and | | | | use of avoparcin, an animal growth |
| human health terms. Healthy ecosystems | | | | promoter, appears to have compromised |
| support a certain level of economic | | | | the utility of vancomycin, the last |
| activity. This is not to say that the | | | | antibiotic effective against |
| ecosystem is necessarily | | | | multi-drug-resistant bacteria. In areas |
| self-sufficient, but rather that it | | | | where avoparcin has been used, such as |
| supports economic productivity to enable | | | | on farms in Denmark and Germany, |
| the human community to meet reasonable | | | | vancomycin-resistant bacteria have been |
| needs. Inevitably, ecosystem degradation | | | | detected in meat sold in supermarkets. |
| impinges on the long-term sustainability | | | | Avoparcin was subsequently banned by the |
| of the human economy that is associated | | | | European Union. Another example is the |
| with it, although in the short-term this | | | | use of ofloxacin to protect chickens |
| may not be evident, as natural capital | | | | from infection and thereby enhance their |
| (e.g., soils, renewable resources) may | | | | growth. This drug is closely related to |
| be overexploited and temporarily enhance | | | | ciprofloxacin, one of the most widely |
| economic returns. Similarly, with | | | | used antibiotics in the year 2000. There |
| respect to social well-being, healthy | | | | have been cases of resistance to |
| ecosystems provide a basis for and | | | | ciprofloxacin directly related to its |
| encourage community integration. | | | | veterinary use. In the United Kingdom, |
| Historically, for example, native | | | | ciprofloxacin resistance developed in |
| Hawaiian groups managed their ecosystem | | | | strains of campylobacter, a common cause |
| through a well-developed social | | | | of diarrhea. Multi-drug-resistant |
| cohesiveness that provided a high degree | | | | strains of salmonella have been traced |
| of cooperation in fishing and farming | | | | to European egg production. |
| activity. | | | | Food and Water Security. Agricultural |
| Another reflection of ecosystem health | | | | practices are also responsible for a |
| lies directly in the public health | | | | growing number of threats to public |
| domain. In spring 2000, a deadly strain | | | | health. Some of these are related to |
| of the bacterium E-coli (0157:H7) | | | | inadequate waste management, which has |
| entered the public water supply in | | | | resulted in parasites and bacteria |
| Walkerton, Ontario, Canada, causing | | | | entering water supplies. Others are of |
| seven deaths and making thousands sick. | | | | entirely different origins and involve |
| This small town, with a population of | | | | apparent transfer across species of |
| five thousand, is in a farming | | | | pathogens that affect both animals and |
| community. Inadequate manure management | | | | humans. The most recent and spectacular |
| from cattle operations was the likely | | | | example is mad cow disease, known as |
| source of this tragedy. | | | | variant Creutzfeldt-Jakob disease in |
| HOW HEALTHY ECOSYSTEMS BECOME | | | | humans, a neuro-degenerative condition |
| PATHOLOGICAL | | | | that, in humans, is ultimately fatal. |
| Stress from human activity is a major | | | | The first case of Bovine Spongiform |
| factor in transforming healthy | | | | Encephalopathy (BSE), the animal form of |
| ecosystems to sick ecosystems. Chronic | | | | the disease, was identified in Southern |
| stress from human activity differs from | | | | England in November 1981. By the fall of |
| natural disturbances. Natural | | | | 2000, an outbreak had also occurred in |
| disturbances (fires, floods, periodic | | | | France, and isolated cases appeared in |
| insect infestations) are part of the | | | | Germany, Switzerland, and Spain. More |
| dynamics of most ecosystems. These | | | | than one hundred deaths in Europe were |
| processes help to "reset" ecosystems by | | | | attributed to what has come to be |
| recycling nutrients and clearing space | | | | commonly called mad cow disease. |
| for recolonization by biota that may be | | | | Improper manure management was the |
| better adapted to changing environments. | | | | likely source of the outbreak of E. coli |
| Thus, natural perturbations help keep | | | | 0157:H7 in Walkerton, Ontario, Canada. |
| ecosystems healthy. In contrast, chronic | | | | Other health risks associated with |
| and acute stress on ecosystems resulting | | | | malfunctioning agroecosystems include |
| from human activity (e.g., construction | | | | periodic outbreaks of cryptosporidiosis, |
| of large dams, release of nutrients and | | | | a parasitic disease that is spread by |
| toxic substances into the air, water, | | | | surface runoff contaminated by feces of |
| and land) generally results in long-term | | | | infected cattle. This parasite causes |
| ecological dysfunction. | | | | fever and diarrhea in immunocompetent |
| Five major sources of human-induced | | | | individuals and severe diarrhea and even |
| (anthropogenic) stresses have been | | | | death in immunocompromised individuals. |
| identified by D. J. Rapport and A. M. | | | | ECOSYSTEM RESTORATION |
| Friend (1979): physical restructuring, | | | | Ecosystem pathology in some cases can be |
| overharvesting, waste residuals, | | | | reversed simply by removing the source |
| introduction of exotic species, and | | | | of stress. In cases, for example, where |
| global change. | | | | ecosystem degradation is the result of |
| Physical Restructuring. Activities such | | | | point-source additions of nutrients or |
| as wetland drainage, removal of shoals | | | | toxic chemicals, removal of these |
| in lakes, damming of rivers, and road | | | | stresses may result in considerable |
| construction fragment the landscape and | | | | recovery of ecosystem health. A classic |
| alter and damage critical habitat. These | | | | case is Lake Washington (near Seattle, |
| activities also disrupt nutrient | | | | Washington). This lake had become highly |
| cycling, and cause the loss of | | | | anoxic (oxygen-depleted) owing to a |
| biodiversity. | | | | sewage outfall entering the lake. |
| Overharvesting. Overexploitation is | | | | Redirecting the sewage outfall away from |
| commonplace when it comes to harvesting | | | | the lake reversed many of the signs of |
| of wildlife, fisheries, and forests. | | | | pathology. |
| Over long periods of time, stocks of | | | | In cases where it is not feasible to |
| preferred species are reduced. For | | | | remove the source of stress, more |
| example, the giant redwoods that once | | | | innovative engineering solutions have |
| thrived along the California coast now | | | | been tried. For example, in the |
| exist only in remnant patches because of | | | | Kyrönjoki and Lestijoki Rivers in |
| overharvesting. When dominant species | | | | western Finland, spring and fall runoff |
| like the giant redwoods (arguably the | | | | leads to sharp pulses of acidity. Spring |
| world's tallest tree-one specimen was | | | | runoff from snowmelt, which releases |
| recorded at 110 meters tall with a | | | | acid from tilled or dug soils, has been |
| circumference of 13.4 meters) are lost, | | | | particularly damaging to fish, during |
| the entire ecosystem becomes | | | | the critical time of year for spawning. |
| transformed. Overharvesting often | | | | Fish reproduction is severely curtailed, |
| results in reduced biodiversity of | | | | if not all together eliminated in highly |
| endemic species, while facilitating the | | | | acidic water. Further there have been |
| invasion of opportunistic species. | | | | massive fish kills resulting from the |
| Waste Residuals. Discharges from | | | | highly acidic waters. One possible |
| municipal, industrial, and agricultural | | | | remedy is to replace the original drains |
| sources into the air, water, and land | | | | which take runoff from the land to the |
| have severely compromised many of the | | | | rivers with new limed drains that can |
| earth's ecosystems. The effects are | | | | neutralize the acidity. This solution |
| particularly apparent in aquatic | | | | has been implemented on an experimental |
| ecosystems. In some lakes that lack a | | | | basis and appears to substantially |
| natural buffering capacity, acid | | | | reduce acidic runoff. |
| precipitation has eliminated most of the | | | | More radical treatments for damaged |
| fish and other organisms. While the | | | | ecosystems involve "ecosystem surgery." |
| visual effect appears beneficial (water | | | | In some cases, invading exotic |
| clarity goes up) the impact on ecosystem | | | | vegetation (such as mangroves in Hawaii) |
| health is devastating. Systems that once | | | | have been removed from regions, and |
| contained a variety of organisms and | | | | native vegetation has been replanted. In |
| were highly productive (biologically) | | | | areas of North America where wetlands |
| become devoid of most lifeforms except | | | | have been severely depleted owing to |
| for a few acid-tolerant bacteria and | | | | farming, urbanization, and industrial |
| sediment-dwelling organisms. | | | | activity, efforts have been made to |
| Introduction of Exotic Species. The | | | | establish new wetlands. |
| spread of exotics has become a problem | | | | More often than not, however, reversing |
| in almost every ecosystem of the world. | | | | ecosystem pathology is not possible. |
| Transporting species from their native | | | | Efforts to restore the indigenous |
| habitat to entirely new ecosystems can | | | | grasslands in the Jornada Experimental |
| wreck havoc, as the new environments are | | | | Range in the southwestern United States |
| often without natural checks and | | | | provide an example. Overgrazing by |
| balances for the new species. In the | | | | cattle has severely degraded the |
| Great Lakes Basin, the accidental | | | | landscape and has lead to replacement of |
| introduction of two small pelagic | | | | the native grasses by largely inedible |
| fishes, the alewife and the rainbow | | | | shrubs, dominated by mesquite. Erosion |
| smelt, combined with the simultaneous | | | | by wind and episodic heavy rains have |
| overharvesting of natural predators, | | | | left areas between shrubs largely bare, |
| such as the lake trout, led to a | | | | and subsequently underlying sands have |
| significant decline in native fish | | | | developed in dune-like fashion over a |
| species. The introduction of the sea | | | | large part of the area. The resulting |
| lamprey, an eel-like predacious fish | | | | mesquite dunes have proven highly |
| that attacks larger fish, into Lake Erie | | | | resistant to efforts to restore the |
| and the upper Great Lakes further | | | | native grasslands, although almost every |
| destabilized the native fish community. | | | | intervention has been tried, including |
| The sea lamprey contributed to the | | | | highly toxic defoliants (Agent Orange), |
| demise of the deepwater benthic fish | | | | fire, and bulldozing. |
| community by preying on lake trout, | | | | Even where it has been possible to |
| whitefish, and burbot. This contributed | | | | restore some of the ecological functions |
| to a shift in the fish community from | | | | of degraded ecosystems, and thus improve |
| one that had been dominated by large | | | | ecosystem health, the restoration seldom |
| benthics to one dominated by small | | | | results in reestablishment of the |
| pelagics (fish found in the upper layers | | | | pristine biotic community. The best that |
| of the lake profile). This shift from | | | | can be achieved in most cases is |
| bottom-dwelling fish (benthic) to | | | | reestablishment of the key ecological |
| surface-dwelling fish (pelagic) has now | | | | functions that provide the required |
| been partially reversed by yet another | | | | ecosystem services, such as the |
| accidental introduction of an exotic: | | | | regulation of water, primary and |
| the zebra mussel. As the zebra mussel is | | | | secondary productivity, nutrient |
| a highly efficient filter of both | | | | cycling, and pollination. In all such |
| phtyoplankton and zooplankton, its | | | | efforts, key indicators of ecosystem |
| presence has reduced the available food | | | | health (vigor, productivity, and |
| in the surface waters for pelagic fish. | | | | resilience) are essential to monitor |
| However, while the benthic fish | | | | progress. Standard ecological indicators |
| community has gained back its dominance, | | | | can be used for this purpose (e.g., |
| the preferred benthic fish species have | | | | measures of productivity, species |
| not yet recovered owing to the degree of | | | | composition, nutrient flows, soil |
| initial degradation. Overall, the | | | | fertility) along with socioeconomic and |
| increasing dominance by exotics not only | | | | human health indicators. |
| altered the ecology, but also reduced | | | | Experience in efforts to restore highly |
| significantly the commercial value of | | | | damaged ecosystems suggests that |
| the fisheries. | | | | ecosystem-health prevention is far more |
| Global Change. Rapid climate change (or | | | | effective than restoration. For marine |
| climate warming) is an emerging | | | | ecosystems, setting aside protective |
| potential global stress on all of the | | | | zones that afford a sanctuary for fish |
| earth's ecosystems. In evolutionary | | | | and wildlife has considerable promise. |
| time, there have of course been large | | | | Many countries are adopting policies to |
| fluctuations in climate. However, for | | | | establish such areas with the prospect |
| the most part these fluctuations have | | | | that these healthy regions can serve as |
| occurred gradually over long periods of | | | | a reservoir for biota that have become |
| time. Rapid climate change is an | | | | depleted in the unprotected areas. Yet |
| entirely different matter. By altering | | | | this remedy is not without its limits. |
| both averages and extremes in | | | | Restoring ecosystem health is not simply |
| precipitation, temperature, and storm | | | | a matter of replenishing lost or damaged |
| events, and by destabilizing the El | | | | biota. It is also a matter of |
| Niño Southern Oscillation (ENSO), which | | | | reestablishing the complex interactions |
| controls weather patterns over much of | | | | among ecosystem lifeforms. Having a |
| the southern Pacific region, many | | | | ready source of healthy biota that could |
| ecosystem processes can become | | | | potentially recolonize damaged |
| significantly altered. Excessive periods | | | | ecosystems is important, but it is only |
| of drought or unusually heavy rains and | | | | part of the solution. |
| flooding will exceed the tolerance for | | | | PREVENTION OF ECOSYSTEM DISRUPTIONS |
| many species, thus changing the biotic | | | | Given the difficulties in reversing |
| composition. Flooding and unusually high | | | | ecosystem degradation, and the many |
| winds contribute to soil erosion, and at | | | | associated human health risks that arise |
| the same time add to nutrient load in | | | | with the loss of ecosystem health, the |
| rivers and coastal waters. | | | | most effective approach is simply the |
| These anthropogenic stresses have | | | | prevention of ecosystem disruption. |
| compromised ecosystem function in most | | | | However, like many common-sense |
| regions of the world, resulting in | | | | approaches, this is easier said than |
| ecosystem distress syndrome (EDS). EDS | | | | done. In both developed and developing |
| is characterized by a group of signs, | | | | countries there is a strong inclination |
| including abnormalities in nutrient | | | | to continue economic growth, even at the |
| cycling, productivity, species diversity | | | | cost of severe environmental damage. |
| and richness, biotic structure, disease | | | | Apart from selfish motivations, the |
| prevalence, soil fertility, and so on. | | | | argument is made that economic growth |
| The consequences of these changes for | | | | has many obvious health benefits, such |
| human health are not inconsiderable. | | | | as providing more efficient means of |
| Impoverished biotic communities are | | | | distributing food supplies, providing |
| natural harbors for pathogens that | | | | more plentiful food, and providing |
| affect humans and other species. | | | | better health services and funding for |
| ECOSYSTEM HEALTH AND HUMAN HEALTH | | | | research to improve standards of living. |
| An important aspect of ecosystem | | | | These are indeed benefits of economic |
| degradation is the associated increased | | | | development, and have led to substantial |
| risk to human health. Traditionally, the | | | | increases in health status worldwide. |
| concern has been with contaminants, | | | | However, at the dawn of the twenty-first |
| particularly industrial chemicals that | | | | century, the past is not necessarily the |
| can have adverse impacts on human | | | | best guide to the future. The human |
| development, neurological functions, | | | | population is at an all-time high, and |
| reproductive functions, and that appear | | | | associated pressures of human activity |
| to be causative agents in a variety of | | | | have led to increasing degradation of |
| carcinomas. In addition to these serious | | | | the earth's ecosystems. As ultimately |
| environmental concerns (where the | | | | healthy ecosystems are essential for |
| remedies are often technological, | | | | life of all biota, including humans, |
| including engineering solutions to | | | | current global and regional trends are |
| reduce the release of contaminants), | | | | ominous. Under these circumstances, a |
| there are a large number of other risks | | | | tradeoff between immediate material |
| to human health stemming from ecological | | | | gains and long-term sustainability of |
| imbalance. | | | | humans on the planet may be the only |
| Ecosystem distress syndrome results in | | | | option. If so, the solution to |
| the loss of valued ecosystem services, | | | | sustaining human health and ecosystem |
| including flood control, water quality, | | | | health becomes one of devising a new |
| air quality, fish and wildlife | | | | politic that places sustaining life |
| diversity, and recreation. One of the | | | | support systems as a precondition for |
| major signs of EDS is increased disease | | | | betterment of the human condition. |
| incidence, both in humans and other | | | | BIBLIOGRAPHY |
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