As Christians, we are called to be true environmentalists. That is, the rational link between the Judeo-Christian worldview and the call to care about and for the planet and its component parts is straightforward and clear.
According to the Scriptures, the universe, the planet Earth, and all of its inhabitants were created by God. Psalm 24 begins this way,
The earth is the Lord's and the fulness thereof, the world and those who dwell therein, for he has founded it upon the seas and established it upon the rivers.Moreover, God gave man (at the very beginning of human history and again later) dominion over the Earth and all of its other inhabitants. This "dominion mandate" is both descriptive and prescriptive. It accurately describes reality. Human beings, with their reasoning (an important aspect of the "image of God" with which they alone of all creatures are endowed by the Creator), do indeed have greater potential and actual impact on the global and local environment than does any other species. The biblical understanding is that this impact can be for good as well as for harm. (By contrast, some of today's most zealous environmentalists see the effect of humans on our planet as only harmful; they deny our potential for being good stewards or carrying out beneficial husbandry.)
The prescriptive aspect of the dominion mandate says that not only do humans have dominion over the planet but that they should take that dominion seriously. We are expected--and accountable to our Creator--to be good stewards of all that he has created.
While the Bible does not teach extensively on this issue (and is largely silent on the how of good stewardship), we can be certain that followers of the one true God are called by him to care for the creation with which he has blessed us. And while being Christian does not automatically give one any expertise in environmental science, it nonetheless behooves us to be salt (a preserving influence) in our generation with regard to creation care. This means (among other things) being responsible with our individual and local resources (indeed, I would argue that we should be on the forefront of such responsibility) as well as educating ourselves so that we might offer and support reasonable, well-founded solutions to more widespread environmental issues.
There are at least three reasons that Christians need to be better (than we have been in recent generations) at creation care. The first is simply that we are to obey God in all things, and being good stewards is one of those things he has commanded us. Another is for the sake of the environment itself, for the future generations of humans and other creatures that will need its resources. Many of the decisions our generation faces have greater potential for long-term effects on the future livability of our planet than the decisions of any previous generation. (I am not here denying God's sovereignty over such things, but affirming that that sovereignty involves the free will of the humans he created.) Third, our failure to obey the dominion mandate--the fact that Christians have not maintained a position at the forefront of creation-care issues--represents, for many in our generation, a further barrier to their considering the claims of Christianity.