This week Mr Stirton, a senior staff photographer for Reportage by Getty Images, was awarded the 2014 Wildlife Photojournalist of the Year for his Living with Lions exhibition of South Africa's lion farms, where lions are captivity-bred specifically to be killed by wealthy hunters.

It is the second year in a row Mr Stirton has won the award, which is presented annually by the Natural History Museum of London and the BBC.

"Canned-lion" hunting draws 18,000 hunters to Africa every year, with hunters paying up to $200,000 to kill a lion and keep its skin and skull as a trophy.

Mr Stirton said the trophy hunting industry was an example of the kind of rampant human consumption writ large that his work endeavoured to capture.

"I get drawn to the human-environment intersection where over-expanding population is effectively destroying the balance of the planet," he said.

"The lion story is a significant aspect of that. We're encroaching on their land, on their space."

A South-African native, Mr Stirton said his increasing focus on wildlife destruction in Africa, primarily caused by poaching, was driven by a compulsion to "do something where I felt effective."

"It's a necessary subject. Most people don't know too much about this side of photojournalism," he said.

A single assignment could take months of investigation and preparation, he said, and had led him to some dangerous encounters with poachers.

"It's a war," he said. "The rangers I'm working with are all fully-armed."

Two hundred rangers have been killed in Africa in clashes with poachers in the last decade, he said, but his own safety was a secondary concern.

"These guys regularly put themselves as risk for very little money. I'm much more worried about them."