1) Environmental science: "It is all I allow myself to think about." What? Environmental science; or your desire to help the third world? I find that God responds positively to people who are passionate about things. The one thing I would caution you about is to try and discover where your focus is. God calls us to have our passion for Him be our priority, and then from that, to channel our energies to serve Him. Otherwise, good and proper things, or even spiritual things, can become idols if we allow them to usurp His place. But only you can determine where the priorities lie.

Some good people have been so consumed by their noble activities that they end up really serving themselves! I think the story of Mary and Martha is instructive in this regard. Jesus said to her, "Martha, Martha, you are worried and upset about many [good and noble] things, but only one thing is needed. Mary has chosen what is better [sitting at the Lord's feet and listening to His word], and it will not be taken away from her" (Luke 10:38-41).

2) Resources to encourage people: A good place to start would be the Psalms. 42 and 43 are particularly relevant and helpful: Why are you downcast, O my soul? Why so disturbed within me? Put your hope in God, for I will yet praise Him, My Savior and my God. As a friend of mine once said, "regardless of where you have been, David was there first!" May people have gone through experiences of discouragement, even deep depression. Many of the Psalms express these sentiments. Yet, the Psalmist continues to hang on to the Lord.

Philip Yancey wrote a book, Where is God when it Hurts? You might want to see if it would be helpful.

I would also seek out a wise, well trained, and biblically sensitive Christian counselor. Sometimes people are depressed for experiences they can't even get in touch with, buried deep down within them. A good counselor can often help them get in touch with these buried causes, help them bring them up, and then guide them to deal with them.