World heritage: from Da Vinci to the white rhino.

• Position: Leonardo da Vinci - Convention for the Protection of the World Cultural and Natural Heritage

On the last days of the eighteenth century, a merchant in France bought Europe's largest Romanesque church for a ridiculously small amount of money. He then proceeded to tear it down and sell it, piece by piece. There was no public outcry. The idea of such a symbol of a national-let alone, universal-heritage made of brick, wood or stone was alien in the Age of the Enlightenment, when people were still struggling to digest the recently introduced notion of a universal literary heritage.

It was only after the ravages of the Second World War that a radical and original concept began to capture the imagination of people everywhere: that of a universal cultural and natural heritage.

It meant that certain buildings, objects and environments had to be preserved because they were crucial, tangible evidence of the past, or expressed the essence of a civilization's unique creativity and offered clues for its renewal and future. Or, in fact, were, simply, beautiful. Modest or grandiose, they were all irreplaceable. Their loss would impoverish us all. A brutal test

For 20 years, UNESCO elaborated and promoted the concept. Then, in 1960, it

was brutally put to the test. The precious monuments of the Nile valley were condemned to be submerged beneath the rising waters from the Aswan High Dam. Egypt's economy desperately needed the dam. And, for a moment, it seemed that survival for the living required the destruction of their own history.

But the whole world was mobilized, arguing that it had a right to preserve those monuments. UNESCO launched an international campaign. And with Egypt's full co-operation, archaeologists explored the threatened sites and 22 temples were dismantled and rebuilt on safe ground. The huge complexes of Abu Simbel and Philae have thus been preserved in their entirety.

Six years later, in 1966, the sea inundated Venice, and a wall of water and mud from the Arno River flooded the churches, museums and libraries of Florence. International rescue efforts were quickly organized. Thousands of sculptures, paintings, manuscripts and books were rescued and restored.

By then it was clear that more than a quick and improvised response to such major crises was needed. In 1972, the ground-breaking Convention for the Protection of the World Cultural and Natural Heritage was adopted. It set a permanent legal, administrative and financial framework for international co-operation in this field. Nature and culture, often considered to be in...