Most environmentalists don’t worry about being killed on the job. But for Leng Ouch, it’s been a near-constant danger.

Ouch’s native Cambodia has one of the highest deforestation rates in the world, much of it due to illegal logging under the protection of corrupt government officials. And much of that illicit timber ends up being exported into foreign markets. To combat the practice, Ouch has gone undercover to document the problem’s scale and expose offenders. He has posed as a cook, a driver, a timber dealer, and a tourist. He photographs the damage and sometimes confiscates the equipment used for illegal logging.

The risks he faces cannot be overstated. Cambodia has been called one of the most dangerous countries for human rights and environmental defenders. Some who’ve tried to confront loggers have been gunned down, including a close friend and colleague of Ouch’s who was murdered in 2012 — one of 14 environmental activists killed in Cambodia between 2005 and 2014.

Ouch himself has been harassed and threatened by military police, loggers, and hired thugs. He believes his family is under constant surveillance, and they have frequently gone into hiding. And because of the political sensitivity of his work, many NGOs have been reluctant to associate with him.

But at the same time he has made real gains. His work has helped lead to the government cancellation of nearly two dozen land concessions — together covering some 220,000 acres of forest — that were being used for illegal and environmentally harmful activities. He’s also raised awareness through campaigns appealing to the world to stop the cross-border timber trade that aggravates climate change, and to stop purchasing products from Vietnam and China that use natural timber — largely imported from Cambodia. For his achievements, Ouch was awarded the prestigious Goldman Environmental Prize in 2016.

Ouch admits he worries about the danger his work entails, but he believes the dire need for action outweighs the risks. “We have to put ourselves at risk to write about Cambodia’s reality,” he has said. “It is the only way to protect the forests we have left.”