Plans for a new road that would cause the Serengeti ecosystem to 'collapse' is attracting international concern

The world's greatest migration spectacle – the annual charge of nearly 2 million wildebeest, zebra and other mammals across the Serengeti national park in east Africa – is under threat from plans to build a road across their route.

Twenty-seven conservation experts from around the world have signed an article in the journal Nature condemning the plan, adding to growing international concern that includes thousands of signatures on petitions opposing the Tanzanian government project.

Stopping the herds from reaching their traditional dry-season feeding grounds to the north would, the scientists argue, lead to population crashes in the prey species and the predators that depend on them.

The road scheme could also lead to the "collapse" of the entire Serengeti ecosystem, from the vegetation that acts as a massive store of carbon dioxide to the sight of wild dogs, rhinoceros, lions and cheetah, they say.

"The proposed road could lead to the collapse of the largest remaining migratory system on Earth – a system that drives Tanzania's tourism trade and supports thousands of people," conclude the authors. "Such a collapse would be exceedingly regrettable for a country that has consistently been a world leader in conservation."

The United Nations Educational, Scientific and Cultural Organisation (Unesco) has also issued a statement saying it has "utmost concern" about the proposed road. It has warned that it "could result in irreversible damage to the property's outstanding universal value". In a move that has prompted speculation that Unesco could strip the Serengeti of its status as a world heritage site if the road is built, the body has also asked for a report on "the state of conservation" for its 2011 annual meeting.

About 1.5m hectares (3.7m acres) of savannah grasslands and plains, riverine forest and woodlands make up the Serengeti national park, stretching across northern Tanzania from Lake Victoria halfway to the east coast of Africa, and from the Ngorongoro game park to Kenya's Masai Mara safari region in the north.

Each year more than 1.5 million wildebeest and zebra, accompanied by gazelle and packs of predators, flee north at the end of the wet season, between April and June, to the only permanent river in the region, the Mara, and wetter feeding grounds. Across this vast area they drive a rare ecosystem by eating huge quantities of plant life, recycling nutrients through massive amounts of dung and urine, and trampling seeds across the landscape.

The planned 33-mile road linking Lake Victoria to the east coast ports and Tanzania's largest city, Dar es Salaam, was announced during the 2005 national election won by President Jakaya Kikwete, and is due to begin construction in 2012.

The Nature article was prompted by growing concern that political pressure for the project is mounting in the runup to next month's national elections, said lead author Prof Andrew Dobson, of Princeton University in the US.

The authors argue that once built, the gravel road will attract faster and heavier lorry traffic, including at night, leading to more collisions with wild animals; this in turn will lead to pressure for a tarmac road and a fence along the route, physically barring the migration route.

Similar experiences in other national parks, including Banff in Canada, Mikumi in Tanzania, and the great Kgalagadi Transfrontier national park in southern Africa, along with similar destruction of six of the world's last 24 terrestrial migratory species, including caribou in northern Canada and pronghorns in the western US, make this a real threat, said Dobson. In addition, control over the road and 50 metres either side would be switched from the national park to the roads department, he said.

Instead, opponents – including conservationists working in Tanzania and the tourist industry in Kenya, which fears it will also suffer a great loss of wild animals – want the government to consider an alternative route to the south of the park. Although the lorries would have to travel further, there would be a similar length of road to construct to link existing highways; the income from 90,000 annual tourists to these and other connected game parks would be protected; and five to eight times as many people would benefit from links to trade in a more populated region of the country, they say.

"We're not against road being built, but there's a much better alternative that serves more people, that has a win-win-win of maintaining one of the biggest wildlife sights in the world and one of the biggest carbon sinks," added Dobson.

Other conservation groups that oppose the plan include the RSPB in the UK, the US-based Wildlife Conservation Society, and the Zoological Society of London.

