Sealing gangs working the sub-Antarctic in the late eighteenth and early nineteenth centuries took Antarctic fur seals in enormous numbers, and by the 1820s the species was commercially extinct across most of its range. A remnant survived at South Georgia. Protection in the twentieth century allowed exponential growth, and South Georgia now holds the overwhelming majority of the world population.
The density has consequences ashore. Breeding beaches expanded inland into stands of tussock grass, Poa flabellata, which is trampled and killed under heavy seal traffic. Loss of that habitat affects burrowing petrels and other island fauna, and increased nutrient input alters soil chemistry.
Recent counts complicate the story further. Fur seal numbers at South Georgia have declined since the 2000s, and the decline is often linked to variability in krill availability associated with warming ocean conditions. Whether the current numbers represent an overshoot correcting itself or the start of a longer decline is not yet resolved.