About 75 percent of Africa\'s savannahs and much of the lion population once estimated to live there have disappeared in the last 50 years, a study found. Burgeoning human population growth and subsequent massive land-use conversion has led to a two-thirds drop in the number of lions living on the shrinking savannahs, a study by Duke University and wildlife conservation group Panthera reported. Researchers used Google Earth\'s high-resolution satellite imagery to study savannah habitat across Africa and analyze human population density data to identify areas of suitable habitat currently occupied by lions, a Panthera release said Monday. The analysis found just 67 isolated regions across the continent where significant lion populations may persist, of which only 15 were estimated to contain a population of at least 500 lions, researchers said. \"The reality is that from an original area a third larger than the continental United States, only 25 percent remains,\" Stuart Pimm of Duke\'s Nicholas School of the Environment said. In West Africa lions are classified as Regionally Endangered on the IUCN Red List of Threatened Species. \"Lions have been hit hardest in West Africa, where local governments often lack direct incentives to protect them,\" said Philipp Henschel, Panthera\'s Lion Program Survey Coordinator. \"While lions generate billions of tourist dollars across Eastern and Southern Africa, spurring governments to invest in their protection, wildlife-based tourism is only slowly developing in West Africa. Currently lions still have little economic value in the region, and West African governments will require significant foreign assistance in stabilizing remaining populations until sustainable local conservation efforts can be developed.\"