Disclaimer: The following are personal opinions/understandings and may be disputed and/or outright incorrect according to others.
What exactly they're talking about with "nature" gets pretty fuzzy with green. The kind of obscenely massive critters that it throws out from time to time-your
Krosan Cloudscrapers,
Skarrg Goliaths, and
Worldspine Wurms- aren't "natural" by any conventional meaning of the term. My understanding is that it's less about what actions are being taken and more whether those actions are a necessary and immediate response to circumstance, and whether they make use of available resources to cultivate more. "Adapt and overcome" might as well be green's motto.
As far as green is concerned "nature" is the emergent property of everything in existence striving at all times to survive and multiply to the best of their ability. Sometimes that means someone's going to break an ecosystem over their knee, but that's fine- green isn't static, and it expects everything whose world was just shattered to figure out how to survive in its new environment, or not.