Brazil’s new President, Jair Bolsonaro – known for his misogynistic, racist, homophobic and anti-environmental comments – has raised questions about the future of the world’s fourth-largest democracy with his support for torture and his unapologetic nostalgia for the country’s 1964-85 military dictatorship. But no part of Brazil’s diverse society has more to dread from Mr. Bolsonaro’s coming to power than the country’s already beleaguered Indigenous groups.Over the past five centuries, the number of Indigenous people in Brazil has shrunk from as much as five million to about 895,000, less than 0.5 per cent of the country’s population. Since 2006, their territory – the Brazilian part of the Amazon Basin – has lost forest cover over an area greater in size than the Democratic Republic of the Congo, the world’s 11th-largest country, according to satellite data. Mr. Bolsonaro, perhaps the most right-wing leader of any democracy in the world, has vowed to open up the Amazon rain forest to developers by repealing constitutional safeguards for Indigenous lands, claiming the protected reserves amount to keeping Indigenous people in “zoos.”As if to signal his intent to permit greater destruction of the world’s biggest rain forest, he has appointed a Foreign Minister who believes climate change is an anti-Christian plot by “cultural Marxists” seeking to criminalize red meat, oil and heterosexual sex. And he has appointed an anti-abortion evangelist to head a new ministry overseeing Indigenous groups, women and human rights. To be sure, Brazil is not the only country where Indigenous tribes must confront mounting threats to their ways of life – and their lives. From Canada and the Philippines to Japan and Indonesia, Indigenous people face growing threats of discrimination, marginalization and forced assimilation. As a result, the world’s Indigenous communities are rapidly dwindling in numbers owing to encroachment and the exploitation of their natural resources.With their combined share of the global population shrinking to 4.5 per cent, Indigenous communities are locked in modern-day David-versus-Goliath battles against mining companies, dam builders, oil-palm plantations, loggers, ranchers, hunters, evangelists and military forces. Their rights continue to be violated with impunity despite an international convention obligating governments to protect their lands, identities, penal customs and ways of life. More fundamentally, at a time when environmental degradation and climate change have emerged as mortal threats to humankind, Indigenous peoples’ ways of life, with their premium on maintaining a balance between human needs and the preservation of ecosystems, serve as examples to the wider world.Living close to nature, with their survival tied to ecosystem health, Indigenous communities respect nature as their teacher and protector. Consequently, they tend to understand nature better than modern societies, as was illustrated in late 2004, when a devastating tsunami struck in the Indian Ocean, killing more than a quarter million people across 14 Asian countries. On India’s remote Andaman archipelago, however, close to the epicentre of the earthquake that caused the tsunami, two of the world’s most isolated Indigenous tribes escaped harm by relying on traditional warning systems and moving to higher ground in time.In fact, one of these two groups – the world’s last known pre-Neolithic tribal community, living on coral-fringed North Sentinel Island – made international headlines recently because of a Chinese-American missionary’s covert but fatal expedition to convert its 100 or so members to Christianity. John Allen Chau made repeated forays onto the island over three days, ignoring warnings from the Sentinelese tribe members to leave their community alone.After the decimation of Indigenous tribes under European colonial rule, countries such as Bolivia, Brazil, Ecuador, India and Peru have pursued “no contact” policies toward isolated tribes. These policies are anchored in laws that protect the rights of Indigenous people to live in seclusion on their ancestral lands. Tribal reserves in India’s Andaman archipelago, for example, are off-limits to all outsiders. Intrusions are punishable with a prison sentence.Yet, with the support of a Kansas City-based missionary agency that trained him for the arduous undertaking, Mr. Chau dodged Indian laws and coastal security to make repeated incursions into North Sentinel to convert a highly endangered tribe to his religion, according to his own diary accounts. He undertook his mission just before American Thanksgiving, an annual whitewash of the genocide perpetrated against Native Americans.Contrast the Sentinelese handling of the alien with punishments for unlawful activity or entry in the so-called civilized world: On Mr. Chau’s first intrusion into their peaceful world, the hunter-gatherer Sentinelese did not subject him to Abu Ghraib-style torture or to U.S. President Donald Trump’s “catch and detain” policy, applicable to anyone entering the United States illegally. The Sentinelese, as Mr. Chau acknowledged in his notes, let him go – with a warning not to return.But an undeterred Mr. Chau, using a fishing boat and a kayak, repeatedly stepped ashore, disparaging the island as “Satan’s last stronghold.” The patience of the Sentinelese wore out, and he was likely shot with a bow and arrow. His body was reportedly buried on the beach, in the way the tribe disposes of its own dead.Although local police have filed a case of murder against “unknown persons,” the Sentinelese acted in a way permitted by the “stand your ground” laws in states such as Florida. That self-defence law shields a person from both criminal prosecution and a civil lawsuit “if he or she reasonably believes it is necessary” to use deadly force to prevent harm or death.Mr. Chau – the son of a refugee father who fled China during the Cultural Revolution and converted to Christianity in the United States – described in his notes how he hid from Indian coastal patrols under cover of darkness to make his criminal forays into an island forbidden even to Indians, including military forces. By demonstrating the ease with which one can breach Indian tribal-protection laws and security, he helped highlight the vulnerability of India’s endangered tribes.More broadly, his mission exemplified the threats to Indigenous people who live in total isolation. Today, most of such tribes live in the Amazon Basin, straddling Brazil’s borders with Peru, Ecuador and Bolivia, or in the jungles of New Guinea and India.The isolated tribes have rejected contact with the external world usually after experiencing ghastly violence and deadly diseases brought by outsiders from the time of European colonization, which wiped out many Indigenous communities from Australia to North America. To escape genocide, some tribes fled to the deepest and most inaccessible parts of jungles, where they still live.For example, until 150 years ago, the Andaman archipelago was home to more than two dozen isolated aboriginal communities, whose ancestors left Africa tens of thousands of years ago in a major exodus that provided the earliest inhabitants of Asia and Oceania. Studies have identified a genetic affinity between the Andaman islanders, Malaysia’s tiny Orang Asli Indigenous population and Oceania’s Melanesians.After British colonial excesses, only four Andaman tribes survive. Two of these groups were forcibly assimilated by the British and have become rootless and dependent on government aid. They are likely to vanish much ahead of the other two groups, which are self-sufficient and continue to live in complete isolation.The future of these highly endangered tribes hinges on policies and laws that adequately safeguard their seclusion and privacy from interlopers and encroachers,Likewise in Brazil, three-quarters of the Indigenous communities that were forced to open up to the outside world became extinct, with the rest suffering catastrophic population declines. Since the late 1980s, however, Brazil’s constitutional protections for Indigenous territories have helped many remaining tribes increase their populations – protections Mr. Bolsonaro has now threatened to repeal.The examples from the Amazon Basin and the Andaman islands underscore the potent dangers of forced assimilation for isolated aboriginal people. Forced incorporation usually happens in the name of providing access to better technology, education and health care or, as Mr. Bolsonaro wants, to open up Indigenous lands to resource extraction and other development projects.Today, the world’s Indigenous groups, despite their small and declining share of the global population, manage 80 per cent of Earth’s biodiversity, in part because their ancestral lands make up 22 per cent of the world’s land surface. By preserving forests, lakes, rivers and other ecosystems on their territories, they play an indispensable role in climate-change mitigation and adaptationThere are compelling anthropological and epidemiological reasons to prohibit outsiders from establishing contact with remote tribes. For example, the first waves of European colonization caused a calamitous depopulation of Indigenous societies by introducing smallpox, measles and other infectious diseases to which Indigenous people had no immunity.Modern life is characterized by rampant use of antibiotics, including in meat production, with antibiotic resistance posing a major public-health challenge globally. Secluded people have no antibodies against the outside world’s deadly pathogens.This helps explain why, even in death, Mr. Chau poses a potential threat to the Sentinelese community because of the pathogens he may have brought.To be sure, contact may be perilous for isolated Indigenous groups, but leave-them-alone policies are no guarantee that remote-living tribes will survive. Small, highly inbred groups confront the spectre of dying out completely, irrespective of whether they stay in or come out of isolation.Close rapport with alien culture, however, may be the worst option, speeding up their disappearance. An isolated Indigenous community’s embrace of modern culture usually dooms its existence. This is why remote-living groups choose to stay in isolation and – like the Sentinelese – fire warning arrows at those who seek to encroach on their habitats.Constitutional or legal safeguards for indigenous lands, cultures and lifestyles, as in Bolivia, Brazil, Ecuador, India and Peru, have allowed some endangered tribes to grow. When authorities look the other way, however, these tribes lose out in battles to defend their lands and cultures from miners, loggers, ranchers, evangelists and others.The unpalatable fact is that the clearing of more forests and other ecosystems for cropland, mining, pasture and other purposes continues to contribute to the decimation of isolated Indigenous groups living in peace and contentment.Most such groups are small and very vulnerable. Brazil, in addition to 238 “contacted” Indigenous tribes, has “23 confirmed and 47 potential” Indigenous groups living in complete isolation, according to one study, while Peru has about 15 such “uncontacted” tribes.For scientists seeking to reconstruct evolutionary and migratory histories, tribes living in complete isolation are an invaluable biological asset. As another study has put it, “Isolated populations living in remote and/or inaccessible parts of the world are regarded as biological treasures from the genetic viewpoint. Many of these isolated human groups have remained relatively unknown until very recent times, so that the information provided by population genetic studies can help the scientists in the partial reconstruction of their demographic and evolutionary histories.”The future of these highly endangered tribes hinges on policies and laws that adequately safeguard their seclusion and privacy from interlopers and encroachers, who bring violence, disease and rapacious exploitation.Media labels such as “primitive” and “Stone Age” are racist tags that conjure up false images. Isolated tribe members certainly do not have the luxuries of modern life and use primal tools. But as Indian anthropologist Madhumala Chattopadhyay, who studied the Andaman Indigenous groups, has said, “The tribes might be primitive in their technology but socially they are far ahead of us.”Let’s be clear: Religion has little meaning for Indigenous societies that revere nature and serve as the world’s environmental sentinels. Where Indigenous communities have been converted to a religion – as on India’s now predominantly Christian Great Nicobar Island – the lifestyle changes have been so profound that the traditional Indigenous cultures have been uprooted.Today, the world’s Indigenous groups, despite their small and declining share of the global population, manage 80 per cent of Earth’s biodiversity, in part because their ancestral lands make up 22 per cent of the world’s land surface. By preserving forests, lakes, rivers and other ecosystems on their territories, they play an indispensable role in climate-change mitigation and adaptation.A critical part of the world’s cultural diversity and ecological harmony, Indigenous peoples have much to teach us about how to combat environmental degradation and climate change. In fact, their role as guardians of biodiversity is critical to the search of modern societies for more sustainable lifestyles.brahma chellaney is a geostrategist and author of nine books, including the award-winning water, peace, and warPublished in Daily Times, January 15th 2019.