In the Brazilian Amazon, getting back to nature may really be the healthiest option. Data covering hundreds of municipalities show that people who live near areas under strict conservation protection experience lower incidences of common diseases and infections such as malaria.
As much as a quarter of the global burden of disease—the total impact of illnesses and injuries on the world’s health—has been attributed to poor environmental quality. But so far, little data has been available to back up that estimate. “The connection between conservation and human health seems intuitive to us, but it is not well documented in the scientific literature,” notes Subhrendu Pattanayak of Duke University. That has at times undermined arguments for conservation, since the costs may be better documented than the benefits.
Between 1990 and 2010, Brazil greatly expanded its system of parks and other protected areas in the Amazon, so that such areas now cover 44 percent of the region. Some of these areas are under strict environmental protection—no roads or other land development are allowed. In others, people can reside in a protected area and use its resources as long as they abide by set standards for sustainability. This contrast makes the Brazilian Amazon an ideal place to study the ways environmental health influences human diseases.
Pattanayak and colleagues gathered data on 700 municipalities throughout the Brazilian Amazon and examined the incidence of the three major disease types that are thought to be linked to environmental quality: malaria, diarrhea and acute respiratory infection. As a control, the team also looked at four diseases that are not believed to be associated with local ecology: AIDS, arthritis, leukemia and dengue. Like malaria, dengue is transmitted by mosquitoes, but the disease mostly occurs in urban areas in Brazil.
Incidence of all three environmental diseases, but not the four others, was lower in the strictly protected areas, the researchers report today in the Proceedings of the National Academy of Sciences. But the same pattern was not seen in other areas. Sustainable-use areas and those with roads and mines saw higher incidences of malaria. And indigenous reserves only had lower incidence of diarrheal diseases.
“Relative to multiple- or sustainable-use protected areas, strict protected areas are generally considered to impose more costs on local people in order to produce global public goods like biodiversity conservation,” says coauthor Erin Sills of North Carolina State University. “But our findings suggest that those strict protected areas are also the most effective at generating local public health benefits.”
Strict land protection slows deforestation and discourages people who are susceptible to malaria and other diseases from interacting with the forest. That helps these areas to serve as a barrier to disease transmission. By contrast, malaria incidence was higher when roads were present. Roads did appear to have a benefit when it came to diarrheal diseases, perhaps because they link people to medical services, the researchers posit. Overall, though, the team estimates that Brazil's move to increase protected areas led to reductions of malaria, diarrhea and acute respiratory infections of 6 percent, 2 percent and 1.5 percent, respectively.
Brazil now faces a challenge in consolidating its network of protected areas and preventing illegal logging and deforestation, says Sills. “The fundamental problem is that there are powerful interest groups who would benefit from other uses of the land.” In addition, people in this region tend to associate economic development, especially in the form of deforestation, as the best means for improving public health, she notes.
But that may not be the case. The findings support the idea that nature can be thought of as a form of capital for people living close to protected zones, says Pattanayak. “This 'natural' capital—well-functioning ecosystems—is paying off by keeping people from falling sick.”