There is no question that photography has played a major role in the environmental movement.
What I mean by photographing as a participant rather than observer is that I'm not only involved directly with some of the activities that I photograph, such as mountain climbing, but even when I'm not I have the philosophy that my mind and body are part of the natural world.
Wanting to take a light camera with me when I climb or do mountain runs has kept me using exclusively 35 mm.
Today, I'm very careful not to mention very specific locations when I write or give captions.
There's no question that photographs communicate more instantly and powerfully than words do, but if you want to communicate a complex concept clearly, you need words, too.
The reason that I keep writing is that all my most powerful messages about the fates of wild places that I care about need to have words as well as images.
The landscape is like being there with a powerful personality and I'm searching for just the right angles to make that portrait come across as meaningfully as possible.
The combination of pictures and words together can be really effective, and I began to realise in my career that unless I wrote my own words, then my message was diluted.
One of the biggest mistakes a photographer can make is to look at the real world and cling to the vain hope that next time his film will somehow bear a closer resemblance to it.
My mountaineering skills are not important to my best photographs, but they do add a component to my work that is definitely a bit different than that of most photographers.
My first thought is always of light.
Luckily, many other people tell me how they have had a particular landscape photograph of mine in their office or bedroom for 15 years and it always speaks to them strongly whenever they see it.
I think that cognitive scientists would support the view that our visual system does not directly represent what is out there in the world and that our brain constructs a lot of the imagery that we believe we are seeing.
These days, most nature photographers are deeply committed to the environmental message.
I almost never set out to photograph a landscape, nor do I think of my camera as a means of recording a mountain or an animal unless I absolutely need a 'record shot'. My first thought is always of light.