The Millennium Assessment: Tropical Ecosystems and Infectious Diseases

Abstract

The Millennium Ecosystem Assessment (MA) was an international effort to produce a broad view of the current status and trends of ecosystems globally, as affected by human activities, with a major focus on their capacity to maintain the ‘‘ecosystem services,’’ or the benefits that they may provide to society. Although concerned especially with natural systems, the MA has also discussed aspects of cultivated systems and urban systems, as well as the interfaces between them. The three working groups —Conditions and Trends, Scenarios, and Responses—have addressed, to some extent, health issues. The MA assessment of the conditions and trends of the ecosystems has included a chapter (chapter 14) on ‘‘Ecosystem Regulation of Infectious Diseases.’’ It has surveyed the major effects of ecosystem changes on infectious diseases worldwide. Although the geographical focus was global, most of the issues discussed were concerned with problems of the developing world. This is where the major infectious diseases are prevalent and also where the main large-scale modifications of the natural systems are currently taking place. Among the 11 infectious diseases ranked in the assessment as high priority for their large global burden of disease and their high sensitivity to ecological change, only three are not typically from tropical countries: Lyme disease, West Nile virus, and Japanese encephalitis. In assembling the evidence of the links between ecological disturbance or degradation and infectious disease transmission or emergence, three anthropogenic drivers of environmental change have emerged as of great importance: agricultural encroachment into natural systems, water-management schemes (dam building, irrigation, and so on), and bushmeat consumption. These drivers seem to be involved in most cases of disease emergence/resurgence in the tropical world. Indeed, a recent survey of disease emergence has pointed out that the categories of drivers of emergence that have historically predominated in developing countries are those associated with agricultural encroachment into forests, direct contact with infected animals (e.g., bushmeat eating), and the breakdown of public health measures. Conversely, in developed countries, the predominant drivers were those associated with changes in technology/industry: microbial adaptation and interna