if the checklists for Exploration Green Conservancy and Greater Clear Lake are accurate – which is not necessarily true – you could compare those checklists in the system (without downloading the lists) to find unobserved species in Exploration Green: https://www.inaturalist.org/lists/4419264-Exploration-Green-Conservancy-Check-List/compare?page=5&utf8=✓&with=2463558
otherwise, to compare species from two places, you could use the general process i described here: https://forum.inaturalist.org/t/first-observation-on-inat-of-a-certain-species/44845/12, which would effectively compare 2 sets of taxa noted in the “species” section of the Explore webpage.
@kildor has some tools that don’t quite address the case here but potentially could be modified to address it exactly…