The United Nations Environment Program (UNEP) has organized a worldwide photo contest around the theme of challenges confronting environmental diversity. The winners of the contest ''Focus on Your World'' will receive prizes ranging from 500 dollars to 20,000 dollars, and their work will be exhibited from March to September 2005 in Japan.

UNEP sources in Mexico, where the Latin American and Caribbean office is based, told Tierramérica that the contest is the most important of its kind and that hundreds of amateur and professional photographers are expected to participate in the adult, youth and children's categories.

''We know that the extraordinary diversity of life on our planet is endangered. You are invited to enter 'Focus on Your World' and photographically express your hope, joy, anger, and concern for all life on Earth. Send us your photographs. Show us your world,'' says UNEP in its official launch of the contest, which opened this month and lasts through Oct. 24.