The huge growth of global 'ecotourism' industry is becoming an increasing concern for conservationists with mounting evidence that many wild species do not respond well to contact with human beings. Overexposure to tourists has been linked to stress, abnormal behavior. and adverse health effects in species such as polar bears, dolphins and gorillas (大猩猩), says a report in New Scientist. While regulated ecotourism can help conservation efforts by encouraging people to manage endangered species and their habitats, many projects are poorly designed and unregulated, it says. 'Many ecotourist projects are unaudited, unauthorized and merely hint they are based on environmentally friendly policies and operations.' Ecotourism is growing by 10 to 30 percent a year and an estimated 20 percent of tourists are thought to visit a conservation-based project. Philip Seddon, of the University of Otago in New Zealand, said that although most tourist projects conformed to basic guidelines on land use and not scaring wildlife, their full impact was rarely considered. In Africa, gorillas have picked up parasites introduced to their habitat by tourists an mongooses (獴) have caught lung diseases from human beings. Experts said that the answer to the problems was better regulation and supervision of ecotourism. The Galapagos Islands, where visitor numbers are strictly controlled, is a good model. Ecotourism is meant to______.