@h2nick (and then some general ranting)
You forgot the third option: Chop down forests for more oilseed rape for fuel.
I am no environmentalist, and I shall explain why. In my unhuble opinion the current environmental movement has very little care for environments. No environs, just mental, that's how it seems to this poor sod. Still, even I can get worked up about environmental issues from time to time, and right now there are thousands of acres of forest being chopped down to grow crops for bio-fuels. The orangutan is facing the biggest threat for years because of short-sighted biofuel policies.
In fact deforestation is a huge problem in many parts of the world, and these policies are only going to make it even worse. I've seen the impact it can have first-hand while I was in Paraguay, and that was just clearance for food-crops. With the added pressure of biofuel production things just get a whole lot worse, and for no actual benefit.
That's the problem with this whole deal. The science, despite what people insist, is not settled. Anyone who reads the actual IPCC reports and not the policy-maker summaries (or worse, the media's analysis of the summaries) will see that our actual knowledge of atmospheric sciences is still in its infancy, and the so-called consensus has no basis in evidence, being merely an appeal to authority based on a-priori and increasingly fragile assumptions about how the atmosphere works. There is, I would point out, no consensus about Newton's laws of gravity or the fact that heating things makes them warmer. There doesn't need to be an appeal to the authority of consensus because the facts speak for themselves in those rather simplistic instances.
The facts do not speak for themselves in the AGW debate. The models that are used in place of hard data prove nothing except that you can make a program do whatever you like given specific assumptions. They are a logical fallacy, a dead-end, they do not reflect reality, are highly flawed and should not be used as a substitute for empirical evidence. Yet they are. That's just one problem out of any number of problems with the supposedly settled science, but it never makes it in to the summary for policy makers and the media simply ignore it.
So with that out of the way, my rant continues. The current status of global anthropogenic climate change trumps all other environmental concerns to the point where, as I mentioned, short-sighted policies that run counter to the very ethos of environmentalism are instigated in the name of "saving the planet". These policies are looked on with approval by the environmental lobby - which mostly consists of people like Al Gore - not because they actually achieve anything to save the planet (it's likely any gains made would be wiped out by a few months of heating Gore's pool) but because they are re-directing people's efforts toward the lobbyists' ways of thinking and doing. The fundamental problem is that the environmental movement has been hijacked by strutters and preeners who are more concerned with having people see them than they are with actually doing something constructive. If they believed their own hype then they'd tear down their palaces and mansions and live in energy-efficient homes, and do all their lobbying over the internet rather than flying everywhere in private jets.
They don't do this, ergo they are either callously exploiting the movement for their own self-promotion, or they are lying out of their arses. And in the meantime hundreds of species that could be saved right now, with very little effort, are being threatened with extinction because of policies inspired by these people.
And that's why I'm not an environmentalist.