Ethiopia is clearing large swathes of land and forcibly displacing populations to make room for state-run sugar plantations in the Omo Valley, according to Human Rights Watch.
The rights watchdog said 500,000 people are affected by the land clearance, which covers "virtually" the whole valley in southern Ethiopia. The reports are based on recently released satellite imagery.
"Ethiopia can develop its land and resources but it shouldn't run roughshod over the rights of its indigenous communities," said HRW's Africa director Leslie Lefkow.
There are several large state-run sugar plantations in the Omo Valley and several new projects under way. Sugar production, mainly for export, is a key source of revenue for Ethiopia.
HRW said communities -- mainly pastoralists -- are being forcibly moved under the government's "villagisation" program, which Addis Ababa says will help rural citizens access key services such as education and health care.
"As has been seen in other parts of Ethiopia, these movements are not all voluntary," said HRW.
The lush Omo Valley, a UNESCO World Heritage site, is home to several indigenous tribes, including the 7,000-member Bodi group, often photographed in traditional beaded dress and with lip plates.
Several rivers run through the valley, including the Gibe River, which the government is using to build a number of large hydroelectric dams.
The main tributary for Kenya's Lake Turkana is the Gibe River, and environmental groups have said the dam constructions will dramatically decrease water levels.
With an average income of less than $2 per day, Ethiopia is one of the poorest countries in the world, but also has one of the globe's fastest growing economies.
The Horn of Africa nation is seeking to industrialise its economy, notably in the agricultural sector, in order to boost exports and reach middle income status by 2025.