BADINGILO and BOMA NATIONAL PARKS, South Sudan — Seen from the air, they ripple across the landscape — a river of antelope racing across the vast grasslands of South Sudan in what conservationists say is the world's largest land mammal migration.
The country's first comprehensive aerial wildlife survey, released Tuesday, found about 6 million antelope. The survey over a two-week period last year in two national parks and nearby areas relied on spotters in airplanes, nearly 60,000 photos and tracking more than a hundred collared animals over about 46,000 square miles (120,000 square kilometers).
The estimate from the nonprofit African Parks, which conducted the work along with the government, far surpasses other large migratory herds such as the estimated 1.36 million wildebeests surveyed last year in the Serengeti straddling Tanzania and Kenya. But they warned that the animals face a rising threat from commercial poaching in a nation rife with weapons and without strong law enforcement.
''Saving the last great migration of wildlife on the planet is an incredibly important thing," said Mike Fay, a conservation scientist who led the survey. ''There's so much evidence that the world's ecosystems are collapsing, the world resources are being severely degraded and it's causing gigantic disruption on the planet.''
The east African nation is still emerging from five years of fighting that erupted in 2013 and killed nearly 400,000 people. Elections scheduled for last year were postponed to this December, but few preparations are in place for those. Violence continues in some areas, with some 2 million people displaced and 9 million — 75% of the population — reliant on humanitarian aid, according to the United Nations.
The migration is already being touted as a point of national pride by a country trying to move beyond its conflict-riddled past. Billboards of the migration recently went up in the capital of Juba, and the government has aspirations that the animals may someday be a magnet for tourists.
South Sudan has six national parks and a dozen game reserves covering more than 13% of the terrain. The migration stretches from east of the Nile in Badingilo and Boma parks into neighboring Ethiopia — an area roughly the size of the U.S. state of Georgia. It includes four main antelope, the white-eared kob — of which there are some 5 million — the tiang, the Mongalla gazelle and bohor reedbuck.
The survey said some animals have increased since a more limited one in 2010. But it described a ''catastrophic'' decline of most non-migratory species in the last 40 years, such as the hippo, elephant and warthog. Associated Press journalists flying over the stunning migration of thousands of antelope last week saw few giraffes and no elephants, lions or cheetahs.