The Nile. A mythical river par excellence, it is the longest in the world and shares its Mediterranean soil with the Rhône, its immensity with the Amazon, and its status as a living tree with all the rivers in this series. But it is a strange, paradoxical tree: it grows, thickens, expands and then shrinks as it flows, in the lower part of its trunk, almost paradoxically. It is shaped more than any other by rain and heat, two factors that govern both plants and rivers.

Its crown is born in a world ruled by the monsoon: lakes, plateaus and powerful tributaries such as the White Nile spring forth in lush tropical landscapes. Further down, as the tree descends, the branches become thinner: the Blue Nile and the Red Nile, sometimes dry for part of the year, struggle to maintain their flow. Some disappear under the sand only to reappear with the rains: these are the wadis, the river's ghost branches. The Nile flows through areas where it hardly ever rains, but where life nevertheless depends entirely on it. Such is the moving beauty of that tree.

This contrast, this shifting line between humidity and aridity, is matched by another: that of languages and cultures. In the north, Arabic; in the south, Nilo-Saharan and Bantu languages. Once again, the Nile connects opposites.

Its shape is striking: a long, slender trunk, starting from Lake Victoria and its canopy of powerful tributaries, to the Egyptian delta, a broad and fragile root that sinks into the Mediterranean. Along the way, the trunk thins and loses its branches. It is a desert tree, adapted to drought, which reduces its activity during the dry season in order to survive. The Nile, too, beats like a heart, swelling during the rainy season and then ebbing away. This rhythm has shaped entire civilisations.

But humans messed with the tree. In 1970, the Aswan Dam put an end to seasonal flooding. The heartbeat of the Nile, so vital to the soil and crops, was stopped. Lake Nasser, a vast artificial sea, flooded the river's memory. Ancient Egypt lived to the rhythm of the Nile. East bank: life. West bank: the dead. Today, Islam and hydroelectric power have replaced the gods and sacred silt.

The Nile flows through 11 countries and feeds 257 million people — a shared, disputed, essential river. Who will keep the water, the root, the trunk or the treetop? Who will reap the fruits of the tree? The Nile is as much political as it is geographical. It is the lifeline of a region, as it always happens.

Which tree embodies this river? The date palm, no doubt. It is a tree of the desert, a source of food, its bare trunk rising towards a crown of leaves: like the Nile, it has a dry base and a lush top. It is a symbol of adaptation and continuity. A tree-river with deep roots and precious fruits, torn between abundance and tension.

The Nile date palm, Phoenix Nilus