IN THIS BOOK, the author considers the human relationship with disease since the beginning of recorded time. He contrasts two perspectives on disease. The first focuses on specific causes and remedies, disease by disease, an outlook used to control and eradicate large-scale epidemics and life/public health-threatening phenomena since the middle-late industrial age. The second, an ecological approach, views disease and public health as a cohesive part of a complex environment, with disease agents responding to environmental changes, many of them caused as human societies move from one developmental threshold to another, thereby altering the environment and changing diets and living conditions.

The author describes seven demographic challenges that need be tackled to achieve acceptable levels of social and environmental sustainability in the twenty-first century. These are: the overwhelming majority of global population growth occurring in countries where poverty and unemployment are endemic; Europe’s declining population; the ever-increasing economic, environmental and political pressure for international migration; the predicted rise in global urban populations from the present 50 per cent to 67 per cent by 2030; the predicted tripling in the number of people over 65 by 2050; economic and health resources in low-income countries being increasingly stretched to deal with communicable and non-communicable diseases, especially those associated with poverty and with an ageing population; and the ongoing demographic changes in both high-income countries (with greater proportions of the populations forming pre- and post-employment age groups) and low-income countries (greater proportions being young, unskilled, unemployed adults – leading to social unrest and emigration).

McMichael considers a question debated among environmentalists, namely, is the number of people itself the pivotal environmental factor? The author comes down on the side of consumption levels rather than raw numbers. In another major debate, on the optimum, sustainable size of the global human population, McMichael accepts that without broad agreement on the desirable size of the human population, debates about population policy are conducted in a vacuum. The most serious estimates made since 1980 are mostly in the range of 3–12 billion, with the most recent estimates being the lowest, and with ecologists’ estimates being consistently lower than those of demographers and economists.

The author considers five main determinants of environmental carrying capacity for humankind: food production, fresh water, energy supplies, biodiversity and (combining these), availability of ecologically productive land. As to consumption, he shows that three-quarters of the present population consumes relatively little. If consumption were at US levels, it would require two extra Earths; to provide US-level consumption for 10 billion people would require four extra Earths. For food production, McMichael shows how the Earth could sustainably support 7 billion on a basic, principally vegetarian diet, 4 billion with 15 per cent of energy from animal foods or 3 billion with 25 per cent of energy from animal foods. For energy requirements, 17 billion kilowatts were used globally in 1999, an average of 7.5 kilowatts per person in high-income countries and 1 kilowatt in low-income countries. For biodiversity, McMichael lists eight key factors which are affected by human population numbers: climate regulation, soil fertility, water quality, waste disposal, nutrient recycling, controlling pest species, limiting the spread of infectious diseases, and pollination of flowering plants. McMichael brings these together with the concept of the ecological footprint. Given that the Earth has 9 billion hectares of ecologically productive land – if divided as 2.5 hectares per person – 3.5 billion people could be supported, on the basis of equity again. McMichael’s preference is for solutions