Band Aid in this case refers to a charity fundraising effort started in the 1980s to combat famine in Ethiopia. It included some misleading lyrics in its headliner song:

> Lyrics of the song included description of the country saying, "where nothing ever grows, no rain or rivers flow..."

https://en.m.wikipedia.org/wiki/Band_Aid_(band)

They all don't need to stay alive. They just need some of them to take hold and grow and then spread seeds so that new trees grow, like a normal forest.

The idea is to plant 350 million knowing that a lot won't survive, but that in planting a huge amount, many millions will survive and nature can take over.

Wikipedia puts Seatle at 37.49", Washington State as a whole at 42.2", and Addis Ababa at 45.9". The precipitation figures (for Washington/Seatle) includes snowfall - I think it's about 10:1 snow:rain