泛滥之谜 07

The labyrinth of papyrus provides food and shelter for enormous numbers of fish.

These waters are clearly fertile

But did they nourish the faraway fields of Ancient Egypt?

The world of papyrus is always on the move.

Air sacs in the stem give it great buoyancy.

Huge papyrus rafts drift on the current.

These restless islands of reeds constantly redefine the channels of the waterways.

It's no wonder explorers found the Sudd impenetrable.

A healthy population of dangerous animals

also helps maintain the Sudd's inhospitable reputation.

At this time of the year, the huge swamp is, in fact, shrinking.

Fish become more densely concentrated, making them easier prey.

But it's not just the water that's becoming overcrowded.

White-eared kob retreat into the dwindling grasslands

of the Sudd during the dry season.

When they were last counted, there were thought to be a million of them

One of the greatest concentrations of large animals on Earth

1,000 per square kilometre.

But the overcrowding encourages strange behaviour.

The males are forced to fight over females

by protecting tiny, merely symbolic, territories.

But they aren't the only ones

for which the White Nile is a lifeline in the dry season.