The great thing about living in a democracy is that you can join these parties and change them from within or you can create your own party. There doesn't have to be single green party, if you believe that nuclear power should be considered green you have plenty of options to make it reality. Beyond direct involvement You can protest, you can campaign for it.

For some reason, in countries with strong democracies and pathways for impact the youth tends not to vote. It's beyond my why they think that they are powerless.