Human ecology / by Leon Eisenberg and Norman Sartorius

Human ecology by Dr Leon Eisenberg Professor of Social Medicine and Health Policy, and of Psychiatry, Harvard Medical School, Boston, USA and Dr Norman Sartorius Director of WHO's Division of Mental Health, Geneva T he term ecology was first used by biologists in the 19th century to mean the study of the inter-relationships between organisms and their environment. An ecosystem comprises a circumscribed environment, all the organisms in it, and their reactions to it and to each other. It was not until the 20th century that the notion of human ecology came to the fore, focusing on human populations, their social organization, the characteristics of the environments they inhabit and the technologies they employ. Human ecology aims to study the interactions between human beings and their social, physical and biological environment. It gives insights that can be used to guide actions favouring balance and harmony in the eco- systems of which people are an inte- gral part. Eugene Odom has outlined the importance of the human element in ecology as follows: "Until recently mankind has ... taken for granted the gas-exchange, water-purification , nutrient-cycling and other protective functions of self-maintaining eco- systems, chiefly because neither his numbers nor his environmental mani- pulations have been great enough to affect regional and global balances. Now ... it is painfully evident that such 28 balances are being affected, often detrimentally. The 'one problem, one solution' approach is no longer ade- quate and must be replaced by some form of ecosystem analysis that con- siders man as a part of, not apart from, the environment. Human ecology does not consider disease, health, life-style, and the environment in isolation. It examines them together with their determinants in dynamic systems. It sees disease as an integral part of the ecosystem and recognises that the eradication of a disease may significantly disturb an ecosystem and create more trouble than the disease itself; ecological understanding can help to avert this. The ecological approach to health care is not the same thing as the ecological position adopted by some political parties, which argue that the human environment should neither be changed nor offend aesthetic stand- ards. Industrial disasters affecting the environment have lent support to the "green" movement, which uses the word "ecology" imprecisely so as to rally broad sections of electorates. In reality, ecology studies but does not oppose changes in the environment or in the functioning of the ecosystem, which are, in any case, inevitable. It also helps to foresee the possible consequences of changes proposed by various sectors. K. Cudlin/WHO photo competition © That the "one problem, one solu- tion" approach no longer works is evident in the failure of attempts to control disease by applying single measures; for instance the use of DOT against malaria vectors. It is also evident in the disasters that have occurred when irrigation projects for arid zones have led to the rapid multiplication of disease vectors, thus increasing the burden of transmissible disease; when forests have been cleared for the cultivation of crops and severe erosion of topsoil has resulted; and when the aggregation of industrial plants in densely populated areas has seriously compromised air quality, with a consequent increase in chronic respiratory disease. Economic development Human ecology can help to explain disease. Take, for example, the changes that have occurred in the causes of mortality in "western" industrialised countries since the start of this century. In 1900 the three leading causes of death in the USA were pneumonia, tuberculosis, and diarrhoea) disease. By 1940, however, pneumonia had dropped to fifth, and tuberculosis to seventh place, and diarrhoea) disease was no longer one of the first ten causes of death, even though there were still no effective medical treatments for any of these WOR LD HEALTH, J anuary -Februa ry 1990 diseases. What, then, accounted for their rapid reduction? Safe water supplies, the pasteurisation of milk, the sanitary disposal of sewage, and less crowding in dwelling-places had sharply reduced exposure to the causal agents; improvements in nutrition and in general health made possible by economic development had increased resistance to disease. By 1980, mortality from tuberculosis had become relatively inconsequential in the USA; deaths from pneumonia had continued to diminish, and those that still occurred were predominantly among older patients affected by other chronic diseases. The gains in the control of infection over the last 40 years reflect the introduction of effective chemotherapy in the 1940s and subsequent advances in this field. But some morbidity patterns have changed for reasons we do not under- stand at all. Thus rheumatic fever, which almost disappeared in western countries, has recently been undergo- ing a resurgence, whereas prevalence rates for stomach cancer in the USA have declined precipitously over the past few decades despite the absence of effective treatment. The more severe forms of hysteria and catatonic forms of schizophrenia have almost dis- appeared, yet other mental diseases, for example depression, show an increase in incidence. Reactions to W ORLD HEALTH. J an ua ry- february 1990 R. Giling © many diseases also seem to have passed through a metamorphosis. The lethality of certain communicable diseases has decreased to a remark- able degree - cholera and plague are good examples. New diseases, AIDS being the most striking example, have made their appearance in devastating fashion. The widespread convictions that the universe of disease is finite and -that every disease will have a cure have both been severely shaken. In recent years, the interaction between people and the world they inhabit has been an arena of major change. The increase of populations whose health has to be improved has reached such dimensions that the application of 19th century public health doctrines is no longer valid. Health care in towns of 20 million inhabitants cannot rest on principles of public health that seemed so useful in towns of less than one million people. Changes in the technologies of trans- porting people, goods and energy, and consequently in the ways in which diseases are spread, have undermined many tenets of community health. Health behaviour has fallen under the influence of a significantly larger number of factors than ever before: this decreases the likelihood of success of many old-fashioned attempts to influence behaviour patterns, even The human element in ecology used often to be overlooked. Today, medicine is paying more attention to human dignity and the quality of life - whether in a hospital setting (left) or in the drought-stricken Sahel. though they may improve health. At one time, medicine had as its main goal the treatment of disease; now it clearly has to pay as much attention to the prevention of disfig- urement and pain, as well as to human dignity and the quality of life. Nine- teenth century medicine aimed to make the health system, and in parti- cular the physician, the final authority in questions concerning the prevention and treatment of disease. In the future, medicine will have to assume a new direction so as to give maximum responsibility to communities and involve other social sectors in the promotion of health and the preven- tion of disorders. Medicine has to develop a health ethic that emphasises an equitable distribution of resources even when this means decreasing the care provided to certain privileged groups. Health will have to be seen as a state of balance between human beings and their environment. Human ecology is the key that can help to develop this approach to health and health promotion. • 29