Tribal groups in Earth’s largest rainforest are already being affected by shifts wrought by climate change, reports a paper published last week in the British journal Philosophical Transactions of the Royal Society B.

The paper, which is based on a collection of interviews conducted with indigenous leaders in the Brazilian Amazon, says that native populations are reporting shifts in precipitation patterns, humidity, river levels, temperature, and fire and agricultural cycles. These shifts, measured against celestial timing used by indigenous groups, are affecting traditional ways of life that date back thousands of years.

“Indigenous groups who have lived in the Amazon for centuries, even millennia, are seeing signs that the climate is changing there,” said Steve Schwartzman, lead author of the study and director of tropical forest policy at Environmental Defense Fund. “Indigenous people are telling us rainfall and river levels have changed; the fires they’re dealing with are different now; and the climate systems they used to depend on for growing crops have become unpredictable.”

In particular, indigenous interviewees mention concerns about drier conditions making it more difficult to control fires traditionally used for small-scale rotational agriculture. For generations, indigenous farmers set fires based on the position of stars in the sky — reflecting the time of year — with the expectation that the fires wouldn’t spread into humid forest areas. But drier conditions today mean that savanna fires can easily move into rainforests, damaging them and reducing their capacity to withstand drought and future burning.



Xingu Basin indigenous lands and protected areas corridor. From Schwartzman et al. 2013. Click image to enlarge.

“I am concerned with the change, today I am very concerned with forest fires… because the savanna and forest are burning,” Arifirá Matipu, a Xingu tribesman is quoted as saying. “Formerly, in the 1970s, these changes had not happened. Until 1980, everything was fine, we set fire to the savanna and it went out by itself, since it stopped right at the edge of the savanna. Starting in 2000, the fires don’t put themselves out anymore… In my village a lot of forest burned. The fire happens because of the heat. We are in a new climate.”

“We know when it is time to clear gardens when we see a star (the Pleiades) that doesn’t always come out, only when its time to make gardens… When the star comes out in the middle of the sky, it’s the time to stop clearing for gardens,” the paper quoted Sadea Juruna as saying. “In the old days the forest was much more humid and because of this only the part cut down caught fire. Today, all the humidity of nature dries up and more places catch fire… The star still comes out,

but the rain is very different. Last year we planted a community garden… and it didn’t grow. The sun got very hot, because the rains were very late. The earth was very dry.”

“Fire is different now. When I was little, people didn’t burn like now. The sun didn’t get as hot as it does now. It always burned and went out,” stated Lahussia Juruna of the Xingu Indigenous Park in an interview. “Now, people set fire and it gets away and there’s a big fire. Before it would burn the savanna but didn’t burn the forest.”

The observations could be partly attributable to land use change in the region. Deforestation can contribute to localized drying, while water diversion for agricultural can reduce stream flows. The study area — the watershed of the Xingu river — is surrounded by large-scale clearing for cattle pasture and industrial soy farms.

Nonetheless, the drier conditions and heightened vulnerability of the rainforest to burning mentioned by the indigenous interviewees have been widely noted across large extents of the southern Amazon. Several recent studies argue that the changes are likely the result of a combination of factors, including warmer temperatures in the tropical Atlantic, fragmentation, and deforestation. Since 2005, the Amazon has experienced the two most severe droughts on record. The droughts isolated river-dependent communities, triggered large-scale forest die-off and carbon emissions, and were associated with massive forest fires.

Some indigenous communities now fear that a spate of dam-construction projects could worsen their plight by restricting river flows, flooding traditional lands, and potentially disrupting fish migration. Especially contentious is the Belo Monte dam, which is currently under construction on the Xingu river itself. Analysts say the project will require at least two upstream dams to make it commercially viable, exacerbating its social and environmental impact.

However not all the news of late out of the Brazilian Amazon has been bad for indigenous residents. The annual deforestation rate in the region has plunged by more than 80 percent since 2004, while several studies showing that indigenous territories have lower deforestation rates has lent support to the argument that land management by native communities can play a key role in protecting forests and reducing greenhouse gas emissions. Accordingly, the authors suggest that indigenous lands and protected areas in the Xingu could be compensated with carbon-linked payments under a Reducing Emissions from Deforestation and Degradation (REDD+) framework should such a policy mechanism emerge under Brazil’s climate change mitigation program.

“The sustainability of indigenous lands and protected areas also depends on sustainable sources of finance,” the authors write. “REDD+ and payment for ecosystem services, whether from public or private sources, have often been proposed as options. A rough estimate, based on modeling of the gradual, bottom-up development of carbon markets from 2015 to 2030 suggests that the value of the Xingu indigenous lands and protected areas under a national emissions trading system might approximate $42 million per year.”

CITATION: Schwartzman S et al. 2013. The natural and social history of the indigenous lands and protected areas corridor of the Xingu River basin. Phil Trans R Soc B 368: 20120164. http://dx.doi.org/10.1098/rstb.2012.0164