Controversial plans to build a tarmac road across the Serengeti National Park have been scrapped after warnings that it could devastate wildlife.
The Tanzanian government planned a two-lane highway across the park to connect Lake Victoria with coastal ports.
But studies showed it could seriously affect animals such as wildebeest and zebra, whose migration is regarded as among the wonders of the natural world.
The government confirmed the road across the park will remain gravel.
In a letter sent to the World Heritage Centre in Paris, the Department of Natural Resources and Tourism says the 50km (30-mile) section of road across the park will "continue to be managed mainly for tourism and administrative purposes, as it is now".
The government is considering an alternative route for a major trade highway that would run to the south of the park.
This would avoid areas of high conservation value, and - although a longer route - would bring the opportunities afforded by a modern transport link to more people.
Last year, a group of scientists warned that the proposed road across the park could bring the number of wildebeest in the park, estimated at about 1.3 million, down to 300,000.
Collisions between animals and traffic would be unavoidable, they said.
And with a corridor on either side of the road taken out of the hands of the park authorities and given to the highways agency, fencing would almost certainly result, blocking movement of the herds.
If wildlife were damaged, they warned, that could also affect the local economy, in which tourism plays a major role.
'Wonder of nature'
The researchers described the Serengeti as "a rare and iconic example of an ecosystem driven by a large mammal migration".
That annual north-to-south trek involves about 1.5 million animals, including wildebeest and zebra.
As the animals travel, they dump vast quantities of urine and dung across the land, fertilising plant growth, while the trampling of hooves also prevents bush from over-growing the grassland.
An impact assessment compiled for the government confirmed the expected impact on migration, adding that the decline of wildebeest and zebra would have a knock-on effect on predators such as lions and cheetahs.
These are among the animals that tourists come to see.
Scientists also warned that the road could bring invasive plant species or unfamiliar diseases into the park, a World Heritage Site.
Last year, the World Heritage Committee expressed its "utmost concern" about the "potentially irreversible damage" that the highway could bring.
Environmental campaigners have welcomed the government's decision, with the organisation Serengeti Watch saying: "A battle has been won".
However, they warned that the region faces a number of other threats, including roads around the park and poaching.