I believe that our attitudes towards people are mirrored in our attitudes toward nature, and our attitudes towards nature are mirrored in our attitudes towards people.
If we think people are "disposable," that they just constitute numbers, that their "utility" needs to be maximised, that some will lose at the benefit of others, that the worth of a human life is his or her ability to contribute to the economy, well, then we will think that nature is "disposable," that nature is just a bunch of numbers (of trees, of parts per million of our pollutants), that the only use of nature is for our aggregate utility, that our mountains and forests here in the "rich" parts of the world will be preserved at the expense of the nature in "poor" parts of the world, that the worth of nature is its ability to contribute to the economy (see for example this article about biodiversity and tree loss). Similarly, if we are willing to blow up the top of a mountain for coal, if we can sleep at night knowing that our pesticides are causing frogs to become hermaphroditic, if we are willing to dam rivers and block their progress, well, then we won't mind blowing people up in the name of "peace," we will allow people to ingest and work with those pesticides, and we will be willing to block indigenous peoples from fighting for their rights and their land.
What this means is that if we are to stand any chance of a less ecologically destructive future, we must come to a peaceableness with other humans. If we are to stand any chance of living in a world in which we respect other humans, we must respect nature. I hope to have conveyed over the past months that there is actually no difference between environmental issues and social issues. They are one and the same. Committing violence against people is the same as committing violence against the land, air, and water. Violence towards land, air and water is the same as violence towards people; it does not take a logical leap to make the connections.