The ideas discussed in his post, especially the idea of rapidly expanding spheres of civilizations consuming all resources in their path, were beautifully explored in Stephen Baxter's sci-fi book, Manifold: Space (a spin-off of his earlier book, Manifold: Time, which is also excellent). In his book, alien intelligences are common; once they become sufficiently advanced, their civilizations tend to rapidly expand and consume all available resources, often to the detriment of other civilizations in their path. This pattern leads to some interesting phenomena: first, while the night sky might seem quiet at first, once we do encounter aliens, we tend to see their signals across many star systems in rapid succession. The reason is pretty obvious: there is only a brief period of time when we are on the surface of a sphere - a few years after our first observations of aliens, we are engulfed within their sphere and observe their signals from all over our stellar neighborhood. Another idea he plays with is the idea of "refugee" species, who attempt to flee oncoming spheres by evacuating ahead of their path instead of being consumed.

Actually, he pushes this idea even further: in the book, our solar system was already engulfed in a few spheres millions of years ago. He suggests that this why Venus is such a hellscape: the aliens came, took the resources they wanted, and left behind a polluted mess. In the case of Venus, they left lots of greenhouse gases behind as the result of some chemical process used to extract resources; as a result, Venus quickly became the warmest planet in the solar system. It's a fun twist on the Fermi paradox: signs of aliens are actually all around us, we are just too dumb to notice them.

Another interesting idea he explores a bit is "ownership" of resources. Do the resource-rich asteroids in our solar system really belong to us? Or are they available to any alien race who happens to pass through? In the book, we first notice aliens by observing unexplainable infrared radiation from the asteroid belt (later revealed to be thermal emissions from their resource extraction). He suggests that these aliens will potentially crowd out humans; even if they are not overtly hostile, they could gobble up all the resources we would have used to expand our civilization.

Highly recommend this book.