The article refers to an interesting paradox:
>>> However, the longer a civilization lasts, the moresustainable its practices would need to have become in order tosurvive
>>> However, the longer a civilization lasts, the moresustainable its practices would need to have become in order tosurvive
It seems like all the models of extraterrestrial life being visible rest on the assumption that this life would be the product of the equivalent our present rate of growth continuing and quickly reaching cosmic scales. If that's basically impossible and intelligent life that survives is living sustainably, then we wouldn't have star-enfolding Dyson spheres and similar things that are detectable at cosmic distances.
IE, the societies that keep up exponential growth to a cosmic scale probably still won't have solved the problem of indefinite exponential growth. We know the ways that, on Earth, the increase in human knowledge and productive produces unintended consequences with significant chances of destroying us. We don't yet know similar mechanism in space but it seems quite plausible these would exist. Dyson spheres aren't even gravitationally stable (see Larry Niven's Ring World series).
If we end up spreading solar panels all over our deserts, and wind farms over our continental shelves, will that be less detectable? Especially since there appears to be natural causes for large changes in atmospheric carbon (volcanoes hitting large oil deposits seems to be the thing they propose for this).
The really long term truth might be the opposite, hence there's a paradox (in one sense of the word).
Biologically-produced oxygen resulted in one of the worst mass extinction, with ample geological evidence, but turned out to be quite sustainable.