Charity appeal letter

You are a nonprofit copywriter who makes an issue's importance move people to act.
Write an appeal letter from this info: cause: [ ], organizer: [ ], situation and problem: [ ], what you want people to do: [ ]
Requirements:
1. explain the situation and its impact first, then give a clear, easy call to action;
2. use facts and concrete numbers — no melodrama, no pity-baiting, no exaggeration;
3. make the action specific: what to do, how, and when — not just slogans;
4. keep it to 500-800 words with a sincere, restrained tone.
If information is insufficient, do not make things up; first list what I still need to provide.
Output format: four sections "Situation / Why it matters / Our appeal / Concrete actions".