Christians have varying interpretations of biblical passages that address the relationship between people and the environment. But there are several points that Christians as a whole agree on, and there are some general biblical themes that should guide Christians in their actions and attitudes regarding environmentalism.
From its opening chapter, the Bible teaches that God created the world and everything in it. And He declared it to be good. In Genesis 1:31, “God saw everything that He had made, and behold, it was very good.” While it is true that the Fall affected every aspect of creation, its original goodness should lead Christians to desire its preservation. Sustaining God’s creation should be a priority for all believers.
God has given the earth to us for our benefit. According to Genesis 1:29, God gave to us “every plant yielding seed that is on the face of the earth, and every tree with seed in its fruit.” But “the earth is the Lord’s and the fulness thereof, the world and those who dwell therein” (Psalm 24:1). We have the freedom to use the earth’s resources for our good, but we should not abuse the resources that God has given us. The earth ultimately belongs to its Creator, and Christians honor God when they care for His creation.
When God created Adam and Eve and placed them into the Garden of Eden, He did so with the intention of having them “work it and keep it” (Genesis 2:15). God’s design, even before the Fall of humanity and the entrance of sin into the world, was for His people to tend to the earth and take care of it. The curse has made that task much harder, but the original task of humanity to work the earth and keep it still applies. We have a responsibility to steward the earth well.
God remains the Sustainer of the universe (Hebrews 1:3, Colossians 1:17). But in His sovereignty and in His providence, He has granted us the privilege and responsibility to manage responsibly the environment that He has created for us. He has entrusted the care of His creation to us, and we must embrace our roles of being caretakers and protectors of it.
But with all of this in mind, we as Christians must remember that we as humans are the crown of creation, uniquely created in the image of God. Though we are called to steward God’s creation well and embrace our roles as caretakers, our greater priority must always be to care for our fellow human beings. That is to say that we should care about protecting baby humans more than protecting baby whales, though protecting baby whales is also a noble (though lesser) cause. And we should prioritize spreading awareness of the saving gospel of Jesus Christ more than spreading awareness about global warming, even if that might be a good cause.
Sometimes, Christians rightly keep these priorities in line when they work to resolve environmental concerns for the sake of giving people a better life. Indeed, in many cases the health of human beings is tied to the health of the planet. Living in the midst of trash or unsanitary conditions inherently makes people more vulnerable. 
As we care for the physical betterment of the marginalized, we must not forget to care for their spiritual betterment as well. Taking care of the environment is a great tool that Christians should use to serve their fellow humans. And it is a great bridge for presenting them with the gospel.
Unfortunately, many Christians mix up these priorities and place caring for the environment above caring for the souls of people. But it is a mistake to participate in acts of social justice that are separated from the gospel. What good is it to give a person a better temporary life on this earth only to have them end up in hell after they die because we focused more on environmentalism than the Great Commission?
The reality is that no matter how well we steward the resources of God’s creation or how well we do our part to protect the environment, it will inevitably pass away one day. In Matthew 24:35, Jesus says, “Heaven and earth will pass away.” He didn’t say “might” or “could.” He said, “will.” We certainly should think about future generations and do our best to preserve the resources of the earth. We should learn about the damaging effects of plastics, and we should strive to reduce, reuse, and recycle. But we must not allow our concerns with environmentalism to slip into idolatry.
In Exodus 20:4, God warns us not to idolize “anything that is in heaven above, or that is in the earth beneath, or that is in the water under the earth.” Paul explains in Romans 1:25 that many people have “exchanged the truth about God for a lie and worshiped and served the creature rather than the Creator.” We must not make the mistake of serving the creation rather than the Creator.
As Christians, we must find the appropriate balance. We take care of the earth while also using it for our benefit according to God’s design. We care for it and don’t abuse it. But we don’t glorify it, and we don’t give it a position in our lives that is higher than it deserves. For God alone is worthy of our worship, and He alone merits sitting on the throne of our lives.
One day, we will get to experience the new heavens and new earth that Revelation 21 describes. We will no longer have sinful natures or sinful tendencies, and we will be able to find the perfect balance of caring for our environment. We won’t fall into the extreme of abusing it, and we won’t fall into the extreme of worshiping it. But until then, we must try our best to live out that balance in the here and now.
Some Christians may feel convicted to do more for the environment than others. Some may become conservation advocates and strategize and implement different sustainable practices. Some may make personal goals to reduce waste. But the central factor driving their decisions must always be obedience to Scripture and a desire to bring glory to God.