Foreign tourists in safari riverboats observe elephants along the Chobe river bank near Botswana's northern border where Zimbabwe, Zambia and Namibia meet in this picture taken March 4, 2005. Botswana's Chobe National Park has one of the highest densities of elephant on the planet - so many that they are gradually turning to forest to savannah - but officials want to avoid being similarly overrun by tourists. Picture taken March 4, 2005. TO MATCH FEATURE BOTSWANA-CHOBE REUTERS/Peter Apps