Several major management*
ah, let’s “manage” the environment, just the way we “manage” companies

actions that would be required to offset*
I hate this word. “offset” it is another of those lovely theoretical business/economic weasel words that doesn’t work the instant you try to use it for anything that does not have a monetary value.

the residual impacts on biodiversity*
either there is an impact or not, what on earth is a residual impact?

appear unattainable, reflecting the high biodiversity value*
ah ha, the key to the matter

of the impacted area, [and] the absence of realistic alternative*
this in pretty direct conflict with the previous line…if an area is highly biodiverse, then there will be species that are simply NOT found elesewhere. Even suggesting that one river can be “swapped” for another is utter toss

riverine systems that could be restored*
so messing one system up is okay as long as “fix” another one..never mind that neither should be “broken” in the first place

to offset the significant residual biodiversity loss*
as near as I can tell, this mean there won’t be little bits of any particular species left after the dam, there will simply be none.