A difference between 'humanistic' and 'orthodox' environmentalist is that they have different evangelions. Orthodox can only have the evangelion of Christ, but humanists have other evangelions - preaching salvation through any human endeavor. Thus the humanist urban planner proclaims paradise through carefully crafted urban planning. Similarly, the humanist environmentalists preach utopia through carbon control or, rather, sustainability.
The Orthodox would say, "the environment hurts because of our passions which we have brought up to a whole larger scale through modern technology and although the technology is not itself bad, we must be careful to live at a human scale and guard ourselves from the passions."
The humanist says, "Sustainability - we must be able to grow in the satiation of our passions at the largest scale possible without threatening our future growth in our passions." Therefore almost always do they determine sustainability at the count of human lives - 'austerity measures' to keep resources to themselves and radical infanticide to prevent others from partaking in the resources. This is why the U.N. has many times been caught sterilizing African women through vaccination and why the U.S. Military has done forced surgical sterilizations in South America.