At the age of 88, most people might prefer to sit back, relax, and leave the hard work to the youngsters. Not Dayton Hyde. The rancher, author, lecturer and conservation activist is a man on a mission to preserve the few unspoiled landscapes left in the West and the wildlife that lives there.

Five decades ago, the World War II veteran, former “Life” magazine photographer and author of 18 books (from “Sandy” in 1968 to his most recent, “All the Wild Horses” in 2006) established a sanctuary on 12,000 acres in the Black Hills of South Dakota that today is home to 600 wild horses. Hyde successfully thwarted attempts to turn the land into a munitions testing site, but is still fighting a uranium-mining project near Mount Rushmore that could pollute underground aquifers with radioactive waste.

That battle is part of the captivating narrative in Susan Mitchell’s documentary "Running Wild: The Life of Dayton O. Hyde,” which opens in select theaters on Oct. 4 and via video on-demand nationwide. Hyde told us why he’s so passionate about wildlife in a recent interview.

MNN: How did your interest in nature and wildlife begin?

Dayton Hyde: From the time I was a little kid and wandered in the woods, they were my friends, and sometimes the only friends I had. I am paying them back for the joys they gave me — that goes not only for horses but any type of wildlife.

Why has it remained your passion and mission?

I felt I hadn't done all I could have done for wildlife conservation. So, at 64 years old I decided to start all over again and do a better job by starting a new wildlife project. To me, horses represent freedom, my own freedom and theirs. I love what they stand for: tough, able to exist in natural environments, beautifully designed to run with the wind in their face and they are able to outrun predators. Wild horses are the first horses I broke. I owe them for a great deal of joy in my life, and now I hope I am paying them back.

Do you identify with them?

Sure. I would like to come back as a wild horse. Somehow when you are riding a horse at a full gallop with the wind in your face, you experience what they are feeling, too. It's like a sailor sitting at the bow of his ship. He becomes part of the wind and part of the sea and part of the world.

Tell me about some of your other conservation efforts — the sandhill cranes and fighting the uranium mining company.

Sandhill cranes are part of a natural world that I loved, and they were disappearing and I thought I could help. Yamsi Ranch in Oregon was in the perfect place for my work with cranes. They created the big sounds on the ranch with their wonderful voices, and I decided to start raising them in captivity and rescuing their eggs from drowning. When I got involved with them they became my good friends. My efforts to raise sandhill cranes eventually helped in the saving the whooping cranes.

In the 25 years that I have worked to build the wonderful Black Hills Wild Horse Sanctuary with the help of Susan Watt, we have created a place for wild horses and all forms of wildlife. The only water we have is from a certain aquifer and this multi-national uranium mining company is now applying to drill through this aquifer by pumping heavy metals and arsenic down into holes to extract uranium. My fear is they will pollute the aquifer, an aquifer that is already polluted from a 1950s mining operation. We will do anything to stop this type of mining from infiltrating our water supply. Uranium is so dangerous and has a hideous afterlife. The Black Hills has two sources of income; agriculture, and tourism, and if you contaminate the water supply for short-term goal, it will wreak irreparable damage to this part of the world. Now our aquifer is being threatened, and we have to ask ourselves, ‘Will what little they gain from this justify what we stand to lose?’ No. Then, after the miners come in to destroy our aquifer, they can just pull out and go back to Canada or where ever else they are based.

It's still too early to say what is going to happen but currently you have just a few board members from different permitting agencies making these decisions that can change the lives of so many people. It should be put up to a public vote, because the majority of the public does not want this mining to happen in the Black Hills.

What's your greatest environmental concern at the moment?

The uranium mining issue and the last 10 years of serious drought. Major weather records have been broken recently so something is happening, and while some say this is a normal thing, I believe it's global warming. Too much is going on to think it is not true. If you don't believe in global warming, you are a damn fool.

What is your life philosophy?

Animals are all important and humans aren't the most important things on this planet. The troubles that the world faces begin in the bedroom. There's not enough water for our growing population, and the next war will be fought over water. There's just not enough water in the U.S. to take care of the people here; people are living longer and we have to be realistic. We are fouling it up at a rapid rate, and that goes for oil and natural gas fracking, too.

What do you know now that you didn't as a young man and wish you did?

Life is too damn short when you have worthwhile causes. You can't do them all and you can't do everything that is needed. One man can do his best with a system of cooperation. He can't do it alone.

What do you consider your greatest accomplishment?

My writing comes first, because I have been able to sell my ideas by way of writing, and people can pick up your ideas from a book, where it is very difficult for them to absorb these ideas when they come from behind a podium. You can get through to people when they can understand things through your writings. And as an author you have to make it fun to read and insert these important ideas through the back door and they become the readers’ ideas and they go on. Some of the ideas I espoused 50 years ago through my writings have become common knowledge now.

Is there anything you still want to do or achieve?

Defeating the uranium mining operation is probably my last big battle, but I hope when I win that one, there will be another one. As long as there is a breath left in me, I will be fighting for wildlife and fighting for the ideas that man is not superlative to the planet. People really created God in their own image and attach a great importance to the human species, but I think all things are important not just the human species, and we have an obligation to protect other species.

What do you want viewers to take away from the film?

I hope that the idea is in there that one man who cares an awful lot can right the wrongs on this planet.

wild horses in South Dakota