During this time of year, Africa’s national parks, conservancies and private game reserves should be teeming with tourists and trophy hunters. But thanks to border closures and crackdowns on international travel, foreigners couldn’t visit these places even if they wanted to.

“It’s very unfortunate,” said Anthony Ntalamo, owner of Tony Mobile Safari, a Botswana-based safari company, who was expecting more than 150 customers in the months to come.

In places like the Okavango Delta and Kruger National Park, where lions, leopards, rhinoceroses, elephants and Cape buffalo are on full display, tourists, hunters and the guides they hire to lead their expeditions have a far greater presence than law enforcement.

Without them, the task of monitoring millions of acres of remote and unforgiving wilderness rests solely on the shoulders of a few thousand rangers.

“Without the tour guides, the rangers are like somebody moving without one leg,” Mr. Ntalamo said.

Nearly all of Mr. Ntalamo’s clients have canceled their upcoming trips. Unless things turn around, he may soon have no choice but to put his 12 employees on unpaid leave.

“People are being laid off in the tourism industry by the dozens in Africa at the moment,” said Andrew Campbell, the chief executive of Game Rangers’ Association of Africa. “All these things are happening because, without tourists, there is no money.”