energy usage has a huge impact on the earth. the most visible effect of course is in global warming, which appears to be at a potential tipping point, including the disappearance of the glaciers, the rise in sea levels, the increasing amount of carbon dioxide and NOx and methane in the atmosphere.
hydrocarbons are poison, period. coal, oil and gas are all terrible pollutants.
actually so is factory farming, which consumes huge amounts of water -- and hidden energy costs in terms of transportation -- as well as polluting waterways with nitrates. and all this ends up in the oceans, parts of which are becoming dead spots where the coral reefs and the fish are dying.
the biggest problems are automobiles and buildings. we have talked about cars quite a lot, but really a huge amount of energy is used up in energy-inefficient buildings. i suspect that buildings that are well-designed can actually be run on nothing but photovoltaic energy based on the sunlight that falls on them.
and there are horribly ridiculous things that we have become used to: for instance, in california, with its abundant sunshine, it is *actually illegal* in many counties to hang out your washing on clotheslines in your yard! that is, you are forced to use up energy to dry your clothes! i wonder how many other such stupid regulations exist.