A couple of weeks ago I mentioned the value of reading preambles in federal register notices to give context to words and processes. While preparing some training materials for my online courses, an example came to mind - the phrases “but for” and “reasonably certain to occur” (sometimes abbreviated to ‘rcto’ just to confuse new practitioners). One or more of those phrases are found in the regulatory definitions for Effects of the Action and Cumulative Effects, and in the regulatory language around incidental take (402.14(g)(7).
A lot of practitioners struggle with their exact meaning. It is probably helpful, but not comforting, to recognize that they don’t have specific definitions in the 402 regulations. The closest the regulations come is in section 402.17 where they are discussed. Perhaps so I can sleep at night, I always viewed the phrases less as a definite threshold and more as trying to represent concepts that then have to be fleshed out in the discussions around their use in biological assessments and consultation documents.
The good news is that in the preambles of 1986 (p. 19931-32), 2015 (pp. 26835, 26837-38), and 2019 (44976, ..981, and 44992-93) the Services tried to express how to think about them and use them in consultation. The handbook also mentions them around page 4-25 and 4-30, but for my money the preamble discussions in 2015 and 2019 (read it here) represent a fuller exploration of the subject. Those preambles spent a fair amount of text trying to outline how to consider and use the phrases. So, if you are struggling with those concepts, it helps to recognize there is not bright line for them and you can tap into the best discussions on their use by reading those preambles.
Ultimately, as with all work in section 7 consultation, it is about using the best data available, to build a rational basis for the conclusion and being transparent about choices made at each step of the way.