Antarctica is a wilderness unique on Earth, and Cape Denison features many of those elements of harsh beauty for which the continent is renowned. Perhaps the most striking natural feature of Cape Denison is the towering height of the Antarctic plateau, which dwarfs Mawson’s Huts. This ice cap extends along Commonwealth Bay in the form of huge ice cliffs, which periodically calve into the sea.

— Management Plan, ASPA 162

While the site is listed nationally and internationally for its historic values, it is also located in a wilderness universally recognised for its unique natural features. The natural setting of the site contributes to its aesthetic values.

The huts, perched on a small rocky peninsula dwarfed by the vast Antarctic ice cap with its snow and ice scapes, rocks and relentless winds, convey a strong sense of time and isolation. As such, the setting meets criterion (e) on both National and Commonwealth Heritage Lists. No further assessment of the natural values of the site has to date been considered necessary, as it seemed outside the scope of management plans focused on the historic site.

The natural values of Antarctica as a whole are comprehensively protected by the Protocol on Environmental Protection to the Antarctic Treaty, which sets aside the entire continent as a natural reserve devoted to peace and science, and establishes requirements for environmental impact assessments preceding activities. This is reflected in Australian legislation. The natural features of the site, including its fauna and flora, are protected by provisions in the management plans Australia prepared for the Antarctic Treaty ASPA and the previous ASMA, which are reflected in the Mawson’s Huts Historic Site Management Plan.

The ASPA management plan notes that there is a ‘paucity of relatively ice-free areas in the immediate region’, and therefore the rocky site offers habitat supporting an important assemblage of fauna and flora. Only approximately 0.3 per cent of Antarctica is ice-free, and the nearest ice-free areas of equal or greater size are approximately 20 km to the east, and approximately 60 km to the west.

In summer (from November), species breeding at or near the site include over 18,000 pairs of Adélie penguins, Wilson’s storm petrels, snow petrels and the south polar skua. Other species sighted in the area include the Cape petrel, Antarctic petrel, southern giant petrel and emperor penguin. Weddell seals, southern elephant seals and leopard seals have been recorded as hauling out and, in the case of elephant seals, moulting at Cape Denison.

The only flora evident at the site are 13 lichen species, identified by the AAE and BANZARE and distributed on boulders and other moraines, and non-marine algae associated with 13 small glacial lakes, generally parallel to the foliation of the basement rocks, and melt streams which flow in summer.