For centuries Kenya's pastoralists have criss-crossed the arid plains of eastern Africa, moving with their families and herds in search of water and grazing pastures.

Trekking vast distances into bordering Somalia and Ethiopia, these nomads carry their homes, Tents made of thatched grass, and their most valued assets, animals, in soaring temperatures and across inhospitable terrain.

Despite the hardship, these migrating populations say their traditional way of life provides all they need, using the meat and milk from their cows, sheep, goats and camels for survival.

But as drought ravages north-east Kenya, drying rivers and turning pastures into deserts, the pastoralists are seeing their animals starve and being forced to rethink their way of life.

Forty-eight year-old Bishar Bukurow Ahmed walked for 16 days in search of water to Modogashe town. After seeing 90 percent of his cattle perish in seven days, Bishar says he will never be able to recover the life he once had.

"This is the worst drought I have ever seen and I think we need to change our ways, maybe we could settle in one place and do something else," he says.

Kenyan President Mwai Kibaki has declared the drought a national disaster. Several million are at risk and at least several dozen people have died already.

The crisis has shocked Kenyans, whose nation is the richest in east Africa. Other countries in the region, particularly Somalia and Ethiopia, are also hit, with six million people on the brink of starvation, according to the United Nations.

MOST VULNERABLE

Aid agencies say a vast majority of those affected are pastoralists, seen as the most vulnerable community as their entire survival is dependent on the climate.

But the failure of rains across three bordering nations has left them unable to use their main coping mechanism: migration.

"Normally a drought is not a serious problem for the pastoralists as they can just move to another area where there have been some rains -- this is their main way of coping," said Ahmed Abdow from the Kenya Red Cross Society.

"But this year (drought) has hit so many countries over such a huge area, that they simply cannot migrate and they have no fallback."

Along the 320 km (200 miles) dirt road from Garissa town northeast to Wajir, rotting carcasses of animals litter the dusty desert-like terrain and vultures circle above, undeterred by the suffocating stench that fills the hot air.

The few surviving cattle in the area are weak and emaciated, unable to keep up with their owners, who say the animals that were once their most valued asset have now become a burden. They cannot feed them yet are also unable to sell them.

If they do find a buyer, earnings are meager -- a third of the price when the drought began in October last year.

Climatic change and cyclical droughts, further compounded by deforestation and land degradation, are taking their toll on Kenya's nomads, many of whom feel they may have to give up the life that previous generations have passed on.

Although few are educated, food security analysts say that with support and rehabilitation they could continue to modify their way of life and use their experience for commercial rearing and trading of animals or opening slaughterhouses.

Others add that improving road networks from these remote, almost forgotten areas to major towns would allow the pastoralists to move easily and be more involved in commercial activities and local business.