Famous People Planting Trees (SLIDESHOW)

Possibly the most popular form of activism on Earth Day -- or around Earth Day -- is the planting of trees. It's a great way to get in touch with nature and fight back against polluters.

Plus, it looks nice. And that's why we get plenty of photo-ops with celebrities planting trees. [See Bill Clinton and the Obamas planting trees for Earth Day 2009] Here are a few from the last couple of years (and one from the '90s -- you'll know which).

Also -- who knew former President Bush spent so much time planting trees?

Check it out:

• • • • • • • • • • • • • • • • • • • Then-Senator Barack Obama and Nobel Laureate Wangari Mathai plant trees in Nairobi in 2006.