"whatever those are" was a poor attempt to indicate that I wasn't sure what people mean by second order effect. was it that something that was not intended, or is it that it happens further in the causal chain, or is it something about particular affordances and general ones (a bridge affords crossing. a bridge that affords crossing both affords crossing a bridge to buy your groceries and crossing a birdge to commit a crime.) Or is it just things that are hard to predict might occur? Or things that have an intervening autonomous moral agent between the engineer and the victim? its not clear to me.

A man-made dam might increase a city's availabe water supply and allow power generation, but it also can increase CO2 emissions and do harm to salmon reproduction. Increased CO2 emissions and detriments to salmon reproductions might contribute to global warming in the first case and an increased price on fresh fish and a declining seal population in the second. Increased price of fresh fish mean less availability to poor consumers and the loss of what might be an otherwise valuable part of diet. Global warming means climage change, sea level rise, an expected increase in unrest, and large scale ecological instability. All those things mean that my daughters may not enjoy the relatively secure life that my generation has led...