A photo is key when it comes to bearing witness and Greenpeace has been a leading organization in visuals for over forty years. We go to the frontline of environmental issues to see for ourselves what is happening so that we can show others.

The marriage between Greenpeace’s campaign knowledge and resources (that include its iconic ships) and world-class freelance photographers has led to many important – and previously untold - stories coming into the public domain.

When I first saw Denis Sinyakov's work I was really impressed. This was in 2010 when he had been commissioned by Greenpeace Russia to shoot in Myslyumovo, one of Russia’s most lethal nuclear dumping grounds. He was working for Reuters at the time and went on to do side projects for Greenpeace in Siberia that included documenting the Indigenous People the Yamalo-Nenets, the Rosneft oil spill and our unique polar bear actions. So last year, when I was tasked with finding a Russian photographer to cover the 2012 Gazprom protest - Denis was the hands down choice.

At Greenpeace International, we have a talent pool of twenty world-class freelance photographers. Denis cemented his spot in this group with his work last year during the Prirazlomnaya action. He was a true journalist – filing on time despite the challenges of working on a ship in the choppy, icy Arctic waters. Well liked among the Greenpeace International crew and activists on board, he showed himself to be a tough and tenacious freelancer. This has been echoed in, what I see, as his clarity of mind in the Murmansk court yesterday. He is a journalist and he will continue to be a journalist.

Freelance photographers who have in the past been commissioned by Greenpeace International have gone on to win top industry awards. Nick Cobbing won a World Press Photo award for his Scientists in the Arctic feature, as did Paul Hilton for his shark fin picture and Daniel Beltrá for his Amazon drought and deforestation images.

All three won their awards for the Nature and Environment section, but there is an even more prestigious World Press Photo category – the Spot News Award. Greenpeace-commissioned freelance photographer Lu Guang won this coveted prize in 2010 for his pictures of an oil spill caused by a pipeline blast at the Dalian Port in China.

This image Denis took on September 18th 2013 that many of us have seen in the papers or online is striking, exposing the oil industry for what it truly is. This photograph is a testament to his professionalism, skill and journalistic nature.

In my professional opinion, as Head of Photography for Greenpeace International, it is powerful because it is a picture of a threat in a bizarre environment; we’ve all seen photos of guns in the context of a conflict or in a blurred CCTV screen grab, but his image is from the waters of the Arctic. He captured a moment so dynamic that there is no way it could have been organized or manipulated. And for this, I believe it has the potential to win the World Press Photo’s Spot News Award.

Denis is a highly regarded freelance photographer in his homeland of Russia. This is marked by the dismay of the country’s photo community at his detention by the Russian authorities in Murmansk. Several Russian media outlets have decided not to publish photos today in protest, or are showing black boxes instead of photos. Like Greenpeace, Denis was bearing witness to an issue that needs to be in the public domain. I, like so many others, call for his immediate release along with the crew of the Arctic Sunrise.

John Novis is Head of Photography at Greenpeace International.