It's high school, folks. And that means it's all about groups, cliques, and clubs. Everyone wants to fit in and belong. Everyone, that is, except Stargirl. She wants to be a member of the biggest group she can imagine—the universe (and all the awesome natural things in it). And we can't help but think she has the right idea. In the world of Stargirl, the smaller the group, the more isolated people become. When you are part of a smaller group, it is considered wrong to care for those who don't belong. On the other hand, if you (like Stargirl) consider yourself as being a part of nature, and the world around you, it's easy to care for and connect with, well, everyone. So, in Stargirl's world, there would be no Team Jacob or Team Edward, only Team Universe.
The farther removed Stargirl is from nature, the less happy she becomes. It is through a connection to the world around us that we feel comfort, security, and peace.
While nature may be pretty and interesting at times, Leo's character shows us that it is not necessary to feel like it is a part of your day-to-day life. You can be happy without nature, as long as you have people to love.