The research found that leopards (Panthera pardus) historically occupied a vast range of approximately 35 million square kilometres throughout Africa, the Middle East and Asia.
However, today they are restricted to approximately 8.5 million square kilometres, researchers said.
Scientists, including those from National Geographic Society's Big Cats Initiative, reviewed more than 1,300 sources on the leopard's historic and current range.
The results show that, while the entire species is not yet as threatened as some other big cats, leopards are facing a multitude of growing threats in the wild, and three subspecies have already been almost completely eradicated.
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"This study represents the first of its kind to assess the status of the leopard across the globe and all nine subspecies," said Jacobson.
The research also found that while African leopards face considerable threats, particularly in North and West Africa, leopards have also almost completely disappeared from several regions across Asia, including much of the Arabian Peninsula and vast areas of former range in China and Southeast Asia.
"Leopards' secretive nature, coupled with the occasional, brazen appearance of individual animals within megacities like Mumbai and Johannesburg, perpetuates the misconception that these big cats continue to thrive in the wild - when actually our study underlies the fact that they are increasingly threatened," said Luke Dollar, programme director of the National Geographic Society's Big Cats Initiative.
"We have discovered the status of the leopard in Southeast Asia is as perilous as the highly endangered tiger," said Philipp Henschel, from Panthera, an international conservation charity.
In many areas, however, habitat is converted to farmland and native herbivores are replaced with livestock for growing human populations.
This habitat loss, prey decline, conflict with livestock owners, illegal trade in leopard skins and parts and legal trophy hunting are all factors contributing to leopard decline, the researchers said.
The study was published in the journal PeerJ.