University of Vermont

PNAS Study: Linking Human Health and Ecosystems

PNAS graph
The complex relationship between altered enviroments and human health is the subject of a new study co-authored by UVM professor Taylor Ricketts. (Image: PNAS)

Since the Greek physician Hippocrates observed that diseases arise from nature -- and not the wrath of gods -- people have understood that human health and the environment are linked. Pollution, radiation and heavy metals are well-known hazards.

But until recently, science has paid little attention to how broad changes in Earth’s natural systems -- like oceans, climate and land cover -- also contribute to both human health and disease.

Now, Taylor Ricketts, director of UVM’s Gund Institute for Ecological Economics, is co-author of a new paper that works to quantify some of these effects -- and point out gaps in our knowledge.

“Human Health Impacts of Ecosystem Alteration,” was published Nov. 11 in the early online edition of the Proceedings of the National Academy of Sciences.

Health outcomes

Looking comprehensively at available research, the paper’s eight authors identified repeated correlations between changes in natural systems and existing and potential human health outcomes, including:

• Forest fires used to clear land in Indonesia generate airborne particulates that are linked to cardiopulmonary disease in downwind population centers like Singapore.

• Risk of human exposure to Chagas disease in Panama and the Brazilian Amazon, and to Lyme disease in the United States, is positively correlated with reduced diversity of mammals.

• When households in rural Madagascar are unable to harvest wild meat for consumption, their children can experience a 30 percent higher risk of iron deficiency anemia -- a condition that increases the risk for sickness and death from infectious disease, and reduces IQ and the lifelong capacity for physical activity.

• In Belize, agricultural runoff hundreds of miles upstream causes a change in the vegetation pattern of lowland wetlands that favors more efficient malaria vectors, leading to increased malaria exposure among coastal populations.

• Human health impacts of human-caused climate change include exposure to heat stress, air pollution, infectious disease, respiratory allergens, and natural hazards as well as increased water scarcity, food insecurity and population displacement.

Strained planet

“Human activity is affecting nearly all of Earth’s natural systems -- altering the planet’s land cover, rivers and oceans, climate, and the full range of complex ecological relationships and biogeochemical cycles that have long sustained life on Earth,” said Samuel Myers of the Harvard School of Public Health and the study’s lead author.

“Defining a new epoch, the Anthropocene, these changes and their effects put in question the ability of the planet to provide for a human population now exceeding 7 billion,” Myers said, “with an exponentially growing demand for goods and services.”

In their paper, the authors also identify gaps in knowledge and outline a research framework that could strengthen the scientific underpinnings of both public health and environmental conservation.

The study also points out equity and inter-generational justice issues related to this field -- since many of the burdens associated with increased degradation of natural systems will be experienced by the poor and by future generations.

“If we can combine forces and utilize sound science to build inter-sectoral bridges where conservation and public health interests are demonstrated to coincide, it's a win-win,” noted co-author Steven Osofsky, from the Wildlife Conservation Society. “On the other hand, if we don’t work together to understand the global burden of disease that’s associated with alterations in the structure and function of natural systems, well, we may find ourselves testing planetary boundaries in ways that are frightening and difficult to reverse.”

More information

Authors include Samuel S. Myers of the Harvard University School of Public Health; Lynne Gaffikin of Evaluation and Research Technologies for Health Inc.; Christopher D. Golden of the Harvard University Center for the Environment; Richard S. Ostfeld of the Cary Institute of Ecosystem Studies; Taylor H. Ricketts of the University of Vermont’s Gund Institute for Ecological Economics; Will R. Turner of Conservation International; and Kent H. Redford and Steven A. Osofsky of the Wildlife Conservation Society.

This work was supported by The Rockefeller Foundation and The Gordon and Betty Moore Foundation as part of the Health & Ecosystems: Analysis of Linkages (HEAL) program. Support was also received from the Bill & Melinda Gates Foundation.

Download a PDF of the full study.