One of the key characteristics of health promotion and the new public health is that it is ecological (Milio, 1987; Martin and McQueen, 1989). The Ottawa Charter for Health Promotion (1986) speaks of a socio-ecological approach to health, and the 'Adelaide Recommendations: healthy public policy' (1988) propose to link the ecological movement and the movement for a new public health. It is necessary, however, to clarify conceptually an ecological public health, to trace the theoretical roots and development of an ecological paradigm in health, and to consider the long-term consequences of an ecological approach to public health.
The concept of an ecological public health has emerged in the past decade in response to a new range of health issues and problems in developed countries. This change can be described as a shift in risk patterns. There are new global ecological risks (such as destruction of the ozone layer and a wide range of environmental hazards and disasters) that pose a risk to health, and health risks are associated with the social, cultural and economic organisations of these societies. These risk patterns tend to be cumulative, have no clear cause and do not allow for simple, straightforward cause-effect interventions. In many cases they tend to be global and finite. Once contracted they can be diagnosed, sometimes alleviated, rarely cured. They generally build up silently and invisibly over time and then emerge as a breakdown in people's bodies and in the social and physical environment. The intervention modes of public health seem ill prepared for this new reality and the risks it poses to the health of populations. This shift has led to a reconsideration of the interdependence of people, their health and their physical and social environments, best illustrated by the mandala of health (Hancock and Perkins, 1985). Building on holistic health approaches developed in the context of the wellness movement, the mandala of health attempts to emphasise the interaction between the mind, body and spirit that constitutes health, but also relates health to the wider concept of an ecosystem that strives for balance. This interaction and interdependence is central to ecological thinking. A new public health approach would therefore not only shift from its present reliance on behavioural epidemiology and surveillance to a more environmental and social approach, but would aim to tackle the risk patterns with an ecological approach.