Unsplash is a wonderful resource for high resolution photographs that you can download and use for anything you wish, no strings attached. You can use it for any design project; be it a mock up or an asset is completely up to you.
Human beings have been shaping the the Earth since the beginning of time. Molding it to our benefit, sometimes to a detrimental point. Indeed, there have been plenty of debates on the impacts of Global Warming and it is an important topic in our time. There is a common phrase, a belief and mantra that exists in most cultures; if you respect mother nature, she will respect you back.