Study Links Intact Amazon Forests on Indigenous Lands to Lower Disease Rates

A new study in Communications Earth & Environment found that parts of the Amazon rainforest that are legally recognized and effectively maintained by Indigenous peoples were associated with lower rates of several human diseases, adding empirical evidence to long-held Indigenous claims that intact forests protect community health.

Researchers compiled and analyzed data on forest quality, legal recognition of Indigenous territories and disease incidence across countries that border and include the Amazon. They report that instances of illnesses, including respiratory conditions linked to smoke from fires and vector-borne diseases such as malaria, were reduced in areas where forest cover was maintained under Indigenous stewardship.

The authors sought to separate the influence of forest protection from other factors that affect health outcomes, such as access to medical care. Paula Prist, a senior program coordinator for the Forest and Grasslands Unit at the International Union for Conservation of Nature and a co-author, said the analysis accounted for variables that could affect disease spread. The team also examined how legal recognition of Indigenous land rights corresponded with forest condition and human health metrics.

Francisco Hernández Cayetano, president of the Federation of Ticuna and Yagua Communities of the Lower Amazon (FECOTYBA), said the findings align with Indigenous knowledge that links human well-being to the surrounding environment. "The ‘forest man’ or ‘man forest,' according to the Indigenous perspective, has always been linked to the reciprocity between human health and the natural environment where one lives," Hernández said. He urged states to guarantee Indigenous rights and territories, saying failure to do so would harm health, lives and ecosystems.

Outside scientists praised the study's ambition and methods while urging caution about interpreting the results as causal. Kristie Ebi, a University of Washington health and climate scientist, called the work "impressive" for highlighting the complexity of factors that affect human health and for suggesting a role for Indigenous communities in shaping healthier landscapes. Magdalena Hurtado, an anthropology and global health professor at Arizona State University, said the study was a useful starting point but cautioned that some specific thresholds reported by the authors — such as their finding that Indigenous territory protections were beneficial only when forest cover exceeded about 40% — may reflect limits of the data and correlational methods rather than precise tipping points.

James MacCarthy, a wildfire research manager with Global Forest Watch at the World Resources Institute who was not involved in the research, noted that there is already a strong body of evidence that Indigenous land tenure tends to help keep forests intact. He said the new study emphasizes the broader public-health implications of forest loss and the importance of protecting forested areas both inside and outside Indigenous stewardship.

Study co-author Julia Barreto, an ecologist and data scientist, said the international team aimed to make information publicly available and to draw attention to the Amazon’s global importance. Paula Prist noted the study's goal was to understand how landscapes can support human health while acknowledging that not all forest landscapes will remain unchanged because of competing needs such as farming and livestock production.

The research arrives ahead of the United Nations climate summit scheduled for November in Belém, Brazil, a city often described as a gateway to the Amazon. Organizers, delegates and Indigenous activists are expected to highlight the role of Indigenous communities in climate action and conservation during the conference. The authors and advocates said the study’s findings are relevant to international negotiations that will address climate and land-use policies.

The researchers used publicly available datasets and statistical approaches intended to control for confounding factors, but they acknowledge that observational studies cannot definitively prove causation. Hurtado said future research using additional methods and finer-grained data could refine the relationships observed and test whether thresholds like the 40% forest-cover figure hold under other analytical approaches.

The study adds to a growing literature that links land tenure, forest management and environmental governance with ecological and human-health outcomes. By empirically connecting legal recognition of Indigenous territories, conservation of forest cover and reduced disease incidence, the authors said the work supports arguments for strengthening Indigenous land rights as part of strategies to protect both planetary and human health.

The study and reactions to it underscore ongoing debates about how to balance conservation, economic uses of land and public-health priorities in the Amazon basin. Researchers emphasized that maintaining intact forest mosaics can provide multiple services, including carbon storage and disease regulation, and that policy choices about land rights and land use will affect both local communities and global environmental goals.