The Christian tradition has always emphasized prudence, courage, temperance, justice (the four classical virtues), faith, hope, and love (the three theological virtues).
After careful considerations of all factors I'm convinced that prudence based on the principles of justice is the most important virtue when considering the current environmental problems.
Justice...the fair and equal treatment of all the things in nature and the respect for their legal right of existence is the most powerful virtue to motivate humans in protecting the very environment that pivots our life sustainance.
"Listen closely. Even the trees exhale their own sweet love songs that roll off their boughs and echo out to all of creation. Love is always in the air." - Cristen Rodgers
I think most of these said virtues come in a package. One pops up when another is detected. I am not Christian, so i do not classify love and hope as theological. I am knwn for being honest, but today I am very proud to be abe to love others people and all living beings with lots of respect. My goal is to make people the happiest possible, even if when they seem not to deserve it.
Faith and love because when we have love for ourself, love for our neighbor and love for our country the world will be a better place and our environment will be good to live at.
Prudence and love matter to me when it comes to environmental concerns as God created the earth and gave us humans dominion over it. But, I think our selfish nature takes over and we disregard our environment by polluting it. So, being prudent and developing a love for God's creation would helps us to better protect and use our environment for a sustainable future. This recent conference publication can help to shed further light on this issue:
Conference Paper Leveraging Environmental Education for Achieving Sustainability
Let me be contrarian. I think "faith" is perhaps what we DON'T want, when it comes to protecting and preserving the environment from our selfish wants. The idea that we can do whatever we please, because "God will provide," is what too many of us seem to be doing.
Prudence, on the other hand, is my choice. Also some amount of justice, to leave the world a decent place for those to come.
Prudence is obviously relevant since the principle of prudence is internationally recognised in environmental policy (not to be confused with precaution). Temperance puts less pressure on the environment: it is probably the most traditional of environmental virtues. Skip justice (because bisemic), focus on love instead. I am finishing a book on extending love of one’s neighbour to love of all creation (In French, with critical reference to Calvin). Faith & hope are bad ideas in environmental policy. Courage is dicey because it can lead anywhere. Rightly used it is of course indispensable.
I start with hope, in the sense of a positive expectation of the future. Otherwise, why bother. Then, agreeing with most of the respondents, I choose prudence. Though not among the options, I would add compassion. Compassion enables our ability to see our responsibility in the suffering of the earth, each other, and ultimately our self.
Hope is a poor guide to environmental policy. The nuclear power industry relied on the hope that a solution would be found to nuclear waste before it became a problem. Now we have the waste and no solution has been found. Faith is much the same : there are those who have faith, regardless of all evidence, that global warming is not taking place.
Prudence inspired by love is the key. Primum non nocere - first do no harm.