Young people's fascination with television, the Internet, video games and other electronic entertainment is making it more difficult to protect the world's biodiversity, a UN official warned on Tuesday.

Because many young people are urbanised and alienated from nature, they may not realise the value of protecting natural ecosystems and species, said Ahmed Djoghlaf, the United Nations executive secretary on biological diversity.

"Our children are behind their computers, their SMS, their videogames, watching TV. They are living in a virtual world and we need to re-connect them with nature," Djoghlaf told a Southeast Asian biodiversity forum in Manila.

"They don't see how a potato is grown. They just see potatoes at a shelf in the supermarket."

He cited surveys showing children in developed countries spend 95 per cent of their free time watching TV or on the computer, and only five per cent outdoors. Another survey said 20 per cent of American children had never climbed a tree, Djoghlaf said.

Arguing that the lack of education was one of the biggest threats to preserving natural heritage, Djoghlaf cited a survey of Europe in 2009 which found that 60 per cent of the population did not know the meaning of the word "biodiversity".

"How can you protect something you don't know? How can you protect something you've never seen?" he asked.