Table 2.

Description of factors affecting level of fur seal trampling of coastal terrestrial habitats over the past c. 250 years

	Pre-seal exploitation era	During the peak seal exploitation era (late eighteenth and nineteenth centuries)	During seal population recovery period (early to late twentieth century)	1980s–2020s
Seal population levels	High numbers on South Georgia. Much lower, but variable, numbers (as estimated from seal hair presence in sediment cores) on Scotia Arc archipelagos	Seal populations almost driven to extinction on South Georgia and South Shetland Islands	From very low number, rapid population increase, particularly on South Georgia, to level similar to and potentially higher than during the pre-exploitation period	Large increase in numbers towards end of twentieth century, but with evidence of decline in the early twenty-first century potentially linked to complex combination of change in food availability and distribution, and possible competition with recovering whale populations
Seal distribution	Seal populations on sub-Antarctic islands, primarily South Georgia, with smaller populations on maritime Antarctic South Shetland Islands and South Sandwich Islands	Distribution dramatically decreased due to near extinction through over- exploitation	As populations recovered, breeding distribution recovered to pre-exploitation range	Increased southern distribution range of summer-dispersing male seals extending foraging and haul-out range, possibly facilitated by climate change driven retreat of sea ice extent and new foraging opportunities
Whale populations levels	Large whale populations in Southern Ocean, almost certainly larger than exist currently	Populations declined steeply due to overexploitation in the early and mid-twentieth century	Populations of some species slowly increased after whaling industry collapse in the 1960s and international moratorium on whaling introduced in 1986	Increasing recovery of some whale populations in the Southern Ocean
Food availability for fur seals (e.g. krill)	Moderate levels of food availability, as krill also supported some whale, penguin and fish populations	High levels of krill availability due to decline in seal populations and later decline in whale populations, both through human exploitation	Continued high krill availability with slow recovery of whale populations, facilitating fur seal population explosion	Krill availability may be declining as whale populations recover; also potential impact of human krill fishery
Levels of damage to terrestrial communities	Terrestrial ecosystems strongly impacted close to pre-exploitation breeding concentrations of seals (primarily South Georgia, possibly parts of South Shetland Islands)	Little or no damage to terrestrial communities within previous breeding range due to general absence of fur seals and also reduced numbers of elephant seals	Rapid return of damage to coastal sub-Antarctic (South Georgia) terrestrial communities as breeding population of seals recovered; new damage towards the end of the twentieth century to areas previously not exposed to seals (primarily South Orkney Islands) due to high numbers of summer-dispersing males hauling out at coastal sites	Further high levels of damage extending southwards along western Antarctic Peninsula as new coastline and haul-out sites become available due to sea ice retreat linked with climate change