. Once the civilization reaches truly planetary scales, there has to be some feedback on the coupled planetary systems that gave it birth (air, water, rock). This will be particularly true for young civilizations like ours still climbing up the ladder of technological capacity. There is, in other words, no free lunch. While some energy sources will have lower impact—say solar vs. fossil fuels—you can’t power a global civilization without some degree of impact on the planet.
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Once you realize, through climate change, the need to find lower-impact energy sources, the less impact you will leave. So the more sustainable your civilization becomes, the smaller the signal you’ll leave for future generations.