Trophy hunting can play an essential role in the conservation of African wildlife, according to a growing number of biologists.

Now some experts are calling for a program to regulate Africa's sport-hunting industry to ensure its conservation benefits.

According to a recent study, in the 23 African countries that allow sport hunting, 18,500 tourists pay over $200 million (U.S.) a year to hunt lions, leopards, elephants, warthogs, water buffalo, impala, and rhinos.

Private hunting operations in these countries control more than 540,000 square miles (1.4 million square kilometers) of land, the study also found. That's 22 percent more land than is protected by national parks.

As demand for land increases with swelling human populations, some conservationists are arguing