Preserving healthy environments must encompass efforts to protect land, air, water and biodiversity that depends on different ecosystems. A major threat to healthy environments is the global demand for extraction of resources (mining, and industrial production, local population pressures with resultant demands on land, water and other resources. The 2005 Millennium Ecosystem Assessment found that 60% of the world’s ecosystem resources were degraded or used in unsustainable ways (Hassan et al 2005). Local and regional environment degradation may take many forms: chemical and microbiological contamination of water, particulates in the air from forest fires, coal-burning power plants, factories, erosion and contamination of soil, depletion of aquifers, loss of forests and wetlands and many others. Each of these can have effects on agricultural production and nutrition, and also directly on the occurrence of infectious and/or non-communicable diseases.
Without investments in protecting environments and ecosystems, and addressing exposure to environmental threats, there will be an increasing likelihood of nonlinear changes. These are accelerating, or abrupt changes, such as disease emergence, abrupt alterations in water quality, creation of dead zones in coastal waters (reduced level of oxygen causing species to be unable to survive), collapse of fisheries, and shifts in regional climates. Dry land ecosystems, which are characterized by their lack of water, are where human population is growing most rapidly, but poverty is highest.