From their newsletter:
"We're giving you the chance to have a tree planted in your name in the Daintree rainforest. It's easy...visit Change Your Latitude to register, and we'll send you a certificate confirming the location of your very own tree. Tropical North Queensland is home to the World Heritage listed Daintree rainforest, and at over 135 million years old, it's the oldest living rainforest in the world."
To plant a free tree, you need to enter your name, postcode & email address, AS WELL as the email addresses of 5 friends.