it probably wouldn’t be too difficult to calculate yourself, if you were so inclined.
to get iNaturalist country stats, see https://forum.inaturalist.org/t/overview-statistics-of-all-countries/13973/7.
to get population figures, you could use: https://en.wikipedia.org/wiki/List_of_countries_and_dependencies_by_population (or something similar)
and area figures, you could use: https://en.wikipedia.org/wiki/List_of_countries_and_dependencies_by_area (or something similar)