Remote sensing evidence for population growth of isolated indigenous societies in Amazonia

Abstract

Isolated indigenous societies who actively avoid sustained peaceful contact with the outside world are critically endangered. Last year, "Tanaru", the lone surviving man of his tribe for at least 35 years, died in Southwest Amazonia, marking the latest cultural extinction event in a long history of massacres, enslavement, and epidemics. Yet in the upper reaches of the Amazon Basin, dozens of resilient isolated tribes still manage to survive. Remote sensing is a reliable method of monitoring the population dynamics of uncontacted populations by quantifying the area cleared for gardens and villages, along with the fire detections associated with the burning of those clearings. Remote sensing also provides a method to document the number of residential structures and village fissioning. Only with these longitudinal assessments can we better evaluate the current no-contact policies by the United Nations and governments, along with the prospects for the long-term survival of isolated tribes. While the world's largest isolated indigenous metapopulation, Pano speakers in Acre, Brazil, appears to be thriving, other smaller isolated populations disconnected from metapopulations continue to be extremely vulnerable to external threats. Our applied anthropological conservation approach is to provide analyses of publicly available remote sensing datasets to help inform policies that enhance the survival and well-being of isolated cultural groups.

Figure 1

Top: Approximate locations for uncontacted Yanomami in their circular village (shabono), 55 m in diameter, on May 5, 2016. Bottom: example cluster of longhouses (white arrows), each about 20 m long, of uncontacted Pano speakers in Acre, Brazil, on August 6, 2015. High-resolution (50 cm per pixel) WorldView-03 imagery was purchased from Maxar Technologies, Inc.

Figure 2

Similar ecological footprints of cleared area (left) and fires (right) made by uncontacted Pano speakers in Acre. Since 2000 they have spread in three directions and now live in at least four clusters of longhouses and gardens (labeled).

Figure 3

Fire detections (top) and cleared areas (bottom) have increased through time for uncontacted Pano speakers in Acre. Because gardens (mainly sweet manioc) are productive for around three years, a three-year running sum is one way to estimate total productive land. The three-year sums are fit with loess smooth curves. Technological and algorithmic improvements were made to satellite remote sensing that improved detection for fires after 2012 and for cleared areas after 2015. Fires are increasing at a rate of 14% per year since 2012, and cleared areas are increasing at a rate of 17% since 2015.

Figure 4

Uncontacted Yanomami have lived in four different locations in the last 23 years. Location three is notable for the size of its cleared area and 10 fire detections, while the most recent location four is notable because it has two shabonos.