For the study, the researchers reviewed scientific reports on indigenous peoples and primate biodiversity, and then drew their conclusions.
Areas managed or controlled by indigenous peoples tend to have significantly higher primate biodiversity than nearby regions.
That’s the conclusion of a study published in Science Advances, which compared geographic patterns of nonhuman primate biodiversity and human land use.
They have also found that lorises, tarsiers, monkeys and apes whose territories overlap with indigenous areas are less likely to be classified as vulnerable, threatened or endangered than those who live entirely outside indigenous lands.
“There is an imminent extinction crisis among the world’s 521 primate species,” warns Paul A. Garber, an emeritus professor of anthropology at the University of Illinois Urbana-Champaign, who led the research with Alejandro Estrada, a professor at the Institute of Biology at the National Autonomous University of Mexico.
“We know that 68% of these species are vulnerable, endangered or critically endangered and many of them may not survive until the end of the century. Globally, 93% of primate populations are declining,” he adds.
Understanding the conditions that allow primate populations to survive and even thrive is critical to preventing their extinction and preserving their special contribution to the health of forest ecosystems, Garber stresses.
“Most primates exploit forests, where they serve as agents of pollination and seed dispersal,” he explains in a statement. They participate in important predator-prey relationships. They consume insects and small vertebrates. They play a very important role in regenerating forests.”
As they are relatively large-bodied animals, with a slow reproductive rate and a late age of first reproduction, primates are also “one of the first indicator species if there is any disturbance or drastic change in the environment,” he says.
For the study, the researchers reviewed scientific reports on indigenous peoples and primate biodiversity, and performed spatial analysis “to assess the importance of indigenous peoples’ lands in safeguarding primate biodiversity,” they write.
“We found that indigenous peoples’ lands account for 30% of the primate range and that 71% of primate species inhabit them,” they add. As their range on these lands increases, primate species are less likely to be classified as threatened or have declining populations.”
The pattern held even when comparing indigenous lands with regions with roughly the same human population density immediately outside these indigenous territories, and 10, 25, and 50 kilometers from their borders.
“The results were that the human footprint – a measure of infrastructure development and habitat conversion – was significantly higher immediately outside of indigenous peoples’ lands than within them,” Garber notes.
Most of the indigenous groups whose territories overlap with those of non-human primates have an ancestral association with their lands and these animals, and many – though not all – have developed practices and cultural norms that help preserve primate populations and the health of the ecosystem, he points out.
“In addition, indigenous groups have various prohibitions based on their knowledge, culture or religion,” he continues. We cite several cases, for example, where a species of primate can only be hunted for a particular festival. Or a specific species of primate is not hunted when there is excess fruit in the forest, which allows those populations to enter the reproductive state and produce offspring.
There are exceptions to the close relationship between indigenous peoples’ lands and primate biodiversity, says Garber. But most of the exceptions seem to be the result of colonial practices of the last few centuries. For example, in East Africa, large swaths of traditional indigenous lands have been taken from indigenous communities and preserved as national parks, where primate biodiversity remains greater than in the grazing areas that many indigenous peoples continue to inhabit.
In Madagascar, a country that is home to more than 100 primate species, no group meets internationally accepted definitions of indigenous peoples, and none identify as such, the researchers report. The country, a former French colony, has lost nearly 90% of its original forests. About 96% of its primate species, all of them lemurs, are listed by the International Union for Conservation of Nature as threatened (vulnerable, endangered, or critically endangered).
The study is correlative and therefore does not provide direct evidence that indigenous practices explain the greater diversity of primate species on these lands. However, it strongly suggests that “safeguarding the lands, languages, and cultures of indigenous peoples represents our greatest opportunity to prevent the extinction of the world’s primates,” the authors write.