Research drought in the southwest.
After you're finished researching drought, research what happens to wild animals as they slowly die from starvation and lack of water. Look at the pictures. It ain't pretty.
When you're finished there, research what happens when humans impinge on the animals' lands.
After that, learn about progress, civilization, and human growth.
Want to save wild horses; don't breed. Don't move to the west. Don't need a house and community to live in and surely, don't give some developer of lands your money to build a housing development in the wilderness.
Oh, and to whomever it was talking about NV selling public lands; read up and do your own research. Those would be public lands shit on by humans. They've dumped their mattresses, their motor oil, their old refrigerators, and their dead pets on it and then they've driven up and down it with their ATVs and destroyed any habitat for flora or fauna. Those are the public lands sold. But, hey, it's just desert and nothing lives in the desert, right?
You don't like horses rounded up? Don't breed. Don't move west. Don't breed your own mutt horses.
You think it's caused by ranchers of cattle? Don't eat beef; don't buy cow leather or its products.
Otherwise, STFU and go adopt a mustang and learn what wonderful horses they can be.