I have a lot of sympathy for the Green Party on many issues. I essentially believe that Canada should have little or no standing military, we should have a much stronger education system, I think you might as well legalize marijuana at this point, etc, etc. I also believe that the Green Party is right that there is an environmental crisis in this country and the world in genreal.
However, I would not vote for the Green Party for the very simple reason that they believe that a 'market' approach can solve the environmental crisis. In other words, the Green Party is essentially a socially liberal, financially right-wing party.
This is the problem in a nut shell. The Green Party believes that they can shift the tax burden away from income (both personal and corporate) and put the majority of taxes onto the consumption of Carbon. There are two basic problems with this. One is that it would badly hurt rural and low-income people. It doesn't matter how much you attempt to compensate this portion of the population in the short term, they will ultimately suffer a great deal more than wealthy people. That is just the way it is, whether the Greens like it or admit it. The second problem with this tax shift approach is that it is by definition self-defeating. The objective of such a policy is to lower the amount of carbon products that people consume. (This is where they think the "market" forces will kick in). However, in this plan if carbon usage is reduced radically so is the government's taxation revenue and you are going to be forced to shift the taxes back to income anyway.
I don't believe in letting the so-called market solve the problem for which it is responsible in the first place. The answer to the environmental problems is to regulate producers of carbon and carbon producing products, to make huge investments in alternative energy, and to heavily regulate the production and use of chemicals in general. Corporations have demonstrated again and again that they will not be environmentally responsible unless they are forced to be. And alternative producers in advanced technological markets simply need help because the entrance requirements (in financial terms) are simply too high to depend on so called innovation and entrepreneurship.
And let us not forget that environmental organizations and activists have consistently given the NDP higher marks for their environmental policies than the Green Party.