Human health impacts of ecosystem alteration

Human activity is rapidly transforming most of Earth’s natural systems. How this transformation is impacting human health, whose health is at greatest risk, and the magnitude of the associated disease burden are relatively new subjects within the field of environmental health. We discuss what is known about the human health implications of changes in the structure and function of natural systems and propose that these changes are affecting human health in a variety of important ways. We identify several gaps and limitations in the research that has been done to date and propose a more systematic and comprehensive approach to applied research in this field. Such efforts could lead to a more robust understanding of the human health impacts of accelerating environmental change and inform decision making in the land-use planning, environmental conservation, and public health policy realms.

At least since Hippocrates wrote On Airs, Waters, and Places, the natural environment has been viewed as an important determinant of human health. However, over the last century, the field of environmental health has focused increasingly on quantifying exposure–response relationships for toxins encountered in the human-dominated environment: from an initial focus on workplace exposures, to a population-level focus on radiation, heavy metals, air and water pollution, and more recently, to exposure to endocrine-disrupting chemicals. Over this period, relatively little attention has been paid to how changes in the structure and function of Earth’s natural systems might affect human health. Growing evidence that changes in these natural systems can affect human health in a variety of important ways and the increasing pace and extent of these changes has prompted this Perspective. In it, we review current understanding of this field, identify some of its gaps and limitations, and suggest an approach to expanding our understanding.

Human activity is transforming nearly all of Earth’s natural systems. With the human population now exceeding 7 billion people and rapid growth in per capita consumption of goods and services, humanity’s growing ecological footprint is altering the planet’s land cover, rivers and oceans, climate system, biogeochemical cycles, and the functioning of its ecosystems (1). This suite of changes has given rise to the definition of a new geological epoch: the Anthropocene (2).

The arrival of the Anthropocene presents an uncertain future, not only for the biosphere, but for humanity itself. There is widespread debate about the ability of an altered global environment to meet the needs of a growing and prospering human population. Health is one dimension of human well-being that has received particular attention in this discussion. In 2005, for example, 1,360 experts from 95 countries produced The Millennium Ecosystem Assessment (MA), a consensus document evaluating the state of the planet’s ecosystems. The authors concluded that “any progress achieved in addressing the Millennium Development Goals of poverty and hunger eradication, improved health, and environmental sustainability is unlikely to be sustained if most of the ecosystem services on which humanity relies continue to be degraded” (3). At the same time, the Director-General of the World Health Organization underscored that “Nature’s goods and services are the ultimate foundations of life and health” (4).

Despite the intuitive importance of natural systems to human health, the empirical evidence to support these claims has been relatively thin. On one hand, natural systems provide a suite of “ecosystem services” including nutrition, purification of water, protection from natural hazards, and reduction of some infectious diseases (3). On the other hand, extensive human alteration of the natural world has coincided with large improvements in most health indices globally.
Here we explore our current understanding of the human health impacts of alterations in the structure and functioning of Earth’s natural systems. Our goals are to (i) illustrate what is currently known, (ii) identify gaps and limitations that can be addressed by future research efforts, (iii) address the scale of the health burden associated with changes to natural systems, and (iv) propose a research approach that strengthens the practice of both public health and environmental conservation.