When Botswana’s president, Ian Khama, opened a giant $4.9bn diamond mine in the heart of the Central Kalahari Game Reserve in September, there were some notable absentees among the invited guests: the 700 bushmen whose hunter-gatherer families had been the traditional inhabitants of the desert, but who have been exiled to impoverished settlements on the edge of the park and are forbidden to hunt the wildlife.

According to a Survival International report, launched at the World Parks Congress in Sydney, the world’s biggest conservation meeting, the San of the Kalahari are just one among hundreds of tribal peoples who have been evicted or are under threat of expulsion from the world’s 6,000 national parks and 100,000 protected conservation areas, which together are thought to cover nearly 13% of the Earth’s land surface.

The Survival study states: “In an attempt to protect these areas of so-called ‘wilderness’, governments, companies and NGOs forming the conservation industry enforce the creation of inviolate zones free of human habitation. Tribespeople who live in them are expected to change their way of life and relocate. They are given little, if any, choice about what happens.”

Stephen Corry, director of Survival, said: “This [trend] is based on unscientific assumptions that tribal peoples are incapable of managing their lands, that they overhunt, overgraze and overuse the resources on their lands.

“But it is also based on an essentially racist desire by governments to integrate, modernise and control tribal peoples.”

The number of “conservation refugees” forced out of protected areas is growing, as deforestation threatens water sources and aid linked to climate change becomes more widespread. Academic studies suggest that nearly 20 million Africans were evicted from their traditional homes to make way for conservation in colonial times, but that nearly 50,000 people, including pygmy groups, may have been evicted more recently by central African governments and “eco-guards” working for conservation groups. Meanwhile, groups such as the nomadic Masai and the forest-dwelling Batwa have lost much of their traditional land to conservation projects in Kenya and central Africa.

In Thailand, nearly 500,000 people face being evicted in the name of forest and watershed protection, and in India an estimated 100,000 people have been moved out of tiger reserves and national parks. “Globally, many millions of people must live with the threat of eviction hanging over them,” say the report’s authors.

Forest peoples are being removed to protect water resources for burgeoning urban areas. Last month Jim Yong Kim, the president of the World Bank, appealed to the Kenyan president, Uhuru Kenyatta, to resolve a Bank-backed Kenyan conservation project that has led to the eviction of thousands of Sengwer people living in the Embobut forest. That follows the forced removal of thousands of Ogiek families from the Mau forest.

In a new development, governments are using climate change as an excuse to move people out of reserves. Because forests act as carbon “sinks” and can qualify for lucrative carbon credits, governments are threatening to evict indigenous peoples who traditionally cut wood. “Climate change has raised the stakes, leading governments and corporations to anticipate that they can secure vast amounts of money for laying claim to forest,” says Tom Lomax, a human rights lawyer with the Forest Peoples Programme.

The policy of creating “inviolate” core zones for tiger conservation in Indian reserves has also led to many human rights violations, says the study. Last year hundreds of Munda families living inside the Similipal tiger reserve in Odisha “voluntarily” left the national park, but villagers claim they were barely compensated and that promises of land have not been honoured. Earlier this year thousands of tribal people living in the Kanha tiger reserve were also evicted.

Leading Indian conservationist and writer Prerna Singh Bindra, a former member of the Indian National Board for Wildlife, said many families had left tiger reserves in search of a better standard of living. “There has been voluntary relocation of people within tiger reserves – largely driven by people themselves. Thousands have petitioned governments and even courts seeking rehabilitation, as they live in extreme hardship, lacking basic facilities like electricity, healthcare and education in remote forests and seek a better life outside mainstream society, and with better amenities and opportunity. It is a win-win situation for people and wildlife, especially large mammals like tigers and elephants, which need inviolate forests to survive.”

For those who want to stay in their traditional homelands, however, there is mounting concern among environmentalists. Lomax said: “Conservation groups recognise that indigenous peoples have the rights to the lands, territories and resources that they have traditionally owned, yet in practice they continue to exclude local people from using forest and other resources. Many still practise an outdated ‘fortress conservation’ model, which entails eviction and exclusion of all human presence through continued enforcement.”

Research by the Centre for International Forestry Research, the World Bank and academics has found that traditional communities often protect forests and the environment efficiently and cheaply. In a letter last month to Kenyatta, Paul Kibet, secretary of the Sengwer council of elders, said: “We need to change the mindset of the colonial conservation which fails to recognise that these communities’ traditional lifestyles, economies and knowledge is in harmony with nature.”