Can't decide on path in life...?

So I'm attending junior college right now at 16. I know some people spend their entire lives trying to find what they want to do, but I've had two dreams for a long time. I know I'm capable of achieving either. I might change my mind in the future, but I've considered these for a long time, and I'm passionate about them.

My first interest is aiming for a PhD in either Physics or Geoscience. I could either work in a related field or teach at a university. I understand that it would require hard work, and I'm willing to do it. Science has always been fascinating to me, these especially. I might want to gear my Physics towards Astrophysics.

My other interest is to get a BS in Horticulture (possibly double major and get Environmental Science or Ecology, too). In the long-term, even if I do get a PhD, I want to settle down on an organic farm or in an ecovillage. With my Horticulture degree, I could begin that right away and travel through the WWOOF program. I would also have more time to volunteer. I would apply for the Peace Corps, and even if they didn't accept me, I could find other programs and use Habitat for Humanity or a number of other organizations like Greenpeace.

I'm sorry this is so long, but please give whatever advice you can.:)