Gaia’s Lament: Rather strongly averted on Imperial worlds, and always has been even back in the Era of Steel and Steam – it turns out that one of the things that comes along with immortality is the observation that all those problems you expect to crop up in the distant future? They’re still going to be your problems. This translates, via certain other attributes, into a powerful incentive to not shit all over where you eat, sleep, and live.
(In the modern era it helps that the nanoecology makes Gaia’s laments extremely visible right up front, and as such eminently solvable before they turn into big problems.)
It is enforced variably elsewhere, with positive incentives provided by the Accord’s general recognition that garden worlds and their ecologies are really goddamned valuable and thus dim view of people who go around screwing them up – especially since the Accord on Colonization, while not actually a blanket prohibiting things, does make it possible for them to press the notion that such screw-ups shouldn’t be handed any more planets to make a hash of.