I feel like people generally assume that the establishment of a national park means that area will become a paradise for wildlife and plantlike. While establishing a national park is almost certainly better than ripping down forests and nature to build oil pipes or real estate, the massive number of visitors that the natural beauties attract can do some real damage to the nature  of the area.
To be clear, I’m not arguing that we should stop establishing national parks or anything even remotely close to that, but it’s important to understand how we impact the world around us, even when we’re trying to be as kind to it as possible. This short video detailing the disappearance of Zion Canyon’s mountain lions provides a lot of interesting information relating to our unfortunate impact.
Image Credit: National Park Diaries on YouTube