It is important that we teach our children that it is our responsibility to care for the earth. I don’t think you can start too young with this. Keep it positive, and show not only by words but by example ways that we can help the planet. This is not something we can leave to the schools, we must teach these things at home. The following are links to activities that you may find helpful.
http://www.dltk-kids.com/crafts/earth/index.html
http://greenliving.about.com/od/greenprograms/tp/earth_day_kids.htm
http://www.parents.com/blogs/toddlers-kids/2015/04/16/fun/earth-day-activities-for-kids/
espirational.com 
good point. It is a mind set. Food comes from the earth. We need food. No food without the earth. Care for the earth. I feel good about this one. My son is growing “his” passionfruit and I keep the veg and rice washing/cooking water and after cooled, he puts it on the ground around the passionfruit to give it nutrients. ❤
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