A new study published Thursday shows that the formalized tenure of Indigenous lands improves environmental outcomes in the Atlantic Forest in Brazil.

By analyzing the change in forest cover between 1985 and 2019, researchers found that forest cover change was 0.77 percent points higher each year for Indigenous tenured lands compared with those without tenure, signaling a steady decrease in deforestation after tenure.

The study noted that it could be used to justify the return of land to Indigenous peoples.

“Our study focuses on the environmental component of the land tenure story, but it’s also important to emphasize that land tenure is not just about the environment, but also about human rights,” said Rayna Benzeev, lead author of the study and postdoctoral researcher at the UC Berkeley Department of Environmental Science, Policy and Management.

She noted that the study fills a “gap” in broader literature around Indigenous tenure over lands. Unlike previous studies, it does not include extremely remote Indigenous lands — instead it is able to track the effects of Indigenous tenure in the context of centuries of development pressures.

The Brazilian constitution states that Indigenous peoples are the legal original land holders, granting them the right to land. However the return of land tenure to Indigenous peoples has stalled since 2012, with only one indigenous land granted land tenure since then, Benzeev added.

“This new administration has an opportunity to uphold the Brazilian constitution by granting indigenous peoples with territorial autonomy and self determination rights,” Benzeev said. “Because of that timing, I think that it’s interesting that the study is coming out right now.”

Claudia Polsky, a clinical professor of law and director of the Environmental Law Clinic, has been interested in the intersection between environmental sustainability and Indigenous land rights for more than 30 years. She noted that the United States is a “comparative latecomer” to the global discussion of Indigenous land rights and practices.

For example, California has only in the past couple of years had serious public discussions of Indigenous populations’ better handling of wildfire than Western-colonial fire managers.

“This study helps to make the empirical case for giving Indigenous populations full, secure tenure to their traditional lands as a means of achieving the twin goals of ecosystem sustainability and protection of human rights,” Polsky said in an email.

She also stated that she found the results of the study “unsurprising.”

Nazune Menka, an Environmental Law Clinic supervising attorney lecturer, noted that the intersection between environmental activism and Indigenous rights is increasing, and land tenure also increases a community’s physical and cultural wellbeing by supporting traditional livelihoods while also improving environmental outcomes.

In future work, Benzeev noted that she wants to test the social and political outcomes of Indigenous land tenure by taking into account variables like discrimination, evictions, maintenance of original language and traditional livelihood activities.

In order to link Indigenous land tenure and environmental outcomes, the researchers took a causal inference approach, using difference-in-differences regression, a model that allowed them to estimate the impact of a specific event by removing the effects of possible confounding variables.  Instead of looking at just correlation, they could identify a causal claim, according to Benzeev.

By measuring the counterfactual, which was what would have happened if the land did not get tenure, they could compare it with lands that actually received tenure, noted Eric Vance, a co-author of the study, and an associate professor and director at the Laboratory for Interdisciplinary Statistical Analysis at the University of Colorado-Boulder.

He pointed that this causal inference approach allowed the study to make the case of how and why receiving Indigenous land tenure is “so important.”

This refined statistical approach combined with environmental and Indigenous land titling expertise requires the interdisciplinary combination of environmental researchers, Indigenous land titling expertise, data scientists and statisticians, according to Peter Newton, a co-author of the study, and an associate professor at the University of Colorado Boulder.

“This was a fantastic example of an interdisciplinary collaboration,” Vance said. “Because Rayna worked with statisticians and data scientists on this project, together, we were able to come up with a really rigorous answer to her question and we were able to come up with a final result that none of us could have achieved on our own.”