The savannah habitat that sustains African lions has shrunk by 75 per cent over the past half-century, according to a study published in the journal Biodiversity and Conservation, a dramatic loss that could threaten the species’ survival.

The analysis by American, African and British researchers – which suggests the continent’s lion population has declined from 100,000 to roughly 32,000 over 50 years – provides a clear picture of where the animals live and how land-use changes and population growth have put them in jeopardy.

The findings come a week after the US Fish and Wildlife Service announced it will study if African lions should be listed under the Endangered Species Act, a move that would end the importation of trophies into the United States. Several groups petitioned the agency last year to list the species, though some conservationists argue that trophy hunting provides a source of revenue to local communities, which helps keep savannah habitat intact.

Thomas Lovejoy, a science professor at George Mason University, Virginia, said the paper’s authors “have made a historical contribution” by showing how dramatically Africa‘s viable terrain for lions has declined in recent decades. Lions used to roam much of Africa and Eurasia but are now limited to sub-Saharan Africa. Professor Lovejoy said the fact that savannah habitat loss is outpacing the decline of the world’s tropical rainforests “is terrifying when combined with the prospects of population growth and land-use change in Africa”.

The paper’s lead author, Jason Riggio, assembled a team of graduate students to examine high-resolution satellite imagery of Africa from Google Earth to determine what could qualify as suitable lion habitat. They then compared that information with existing lion population data.

Part of the challenge lions face is that when they venture outside national parks, they may kill livestock and come into conflict with humans. Professor Lovejoy said he was optimistic that public pressure will build for officials to take action. The officials will decide within a year whether to list African lions as endangered.

The study does not, however, answer one of the central questions that officials must answer: whether trophy hunting helps or undermines the species’ survival. Jeff Flocken, the director of the International Fund for Animal Welfare‘s Washington office, said Americans are responsible for importing 64 per cent of the lions hunted for sport.

But hunting groups such as Safari Club International and some environmental organisations say a trophy ban could have unintended consequences. Luke Hunter, the president of the wild cat conservation group Panthera, said that even though he finds lion hunting “abhorrent, as a scientist, I have to ask myself whether it can be a tool for conservation”. Mr Hunter added that ending hunting could accelerate the decline in land conservation. “The danger is: you stop that revenue stream, and all those areas are up for grabs.”