I usually think of 'Nature' as the various spirits inhabiting plants, stones, etc. They are both part and apart from the various gods, are generally older than the gods. Because of this, most of the Gods are creatures of things either apart from nature or 'metanatural' concepts: smithing, war, healing, etc. There are 'Gods' of the forest, animals, etc, but they are actually a type of entitiy apart from them. To many humans it makes little difference.
Druids serve the force of nature in three ways; NG, NE, and TN/LN/CN. The NG druids are kind of like the 'forest witch' archetype: patient, kind, healers that use various natural herbs and such. The NE druid uses those same means to bring as much harm and hurt into the world as he can. The Neutral ones are the scary ones, the ones that have far more equitable connections to the world of plants and animals and elementals as well as to the human world. They're the ones making the huge overarching decisions on how much forest to allow humans to cut, how much deer to allow them to take, etc.
Normally none of them are going to go into 'ecoterrorist mode' unless something is not done about a particular inbalance. They don't have problems with dwarves createing mines as long as the poisonous byproducts of that are not dumped into the local river, which would wash all that downstream and start killing trees, making frogs with five heads and stuff like that. They don't have problems with humans going into the woods or even cutting roads through it as long as it's done in a respectful manner, doesn't harm rare stands of plants (ask them first, and they'll simply move the plants, or ask the plants to do it themselves), etc. They don't have a problem with agriculture as long as certain practices are followed (and they have no problem telling people what those practices are); land that yeilds good bounty makes it less likely that the farmers will want to cut more forest to get more farmland.
They have no real problem with civilization as long as they can make people understand that their actions have consequences. No, the lake does not have an infinite amount of fish in it; you can only take so much before affecting that balance. If you screw it up, then there's no fish for anyone at all. Ever again. You can only plant crop X so many times before the land you're planting it in needs rest, or needs to be planted with crop Y. Follow these precepts and this set of instructions and there will be enough for everyone.
Don't follow them at your peril. Sometimes a forest needs to be burned back before it can grow again.
If a wild boar starts making a nuisance of itself in the area, the druid will try to talk it into going elsewhere or find out why it is here. A bear coming down to raid human garbage will get the same talking to.