Spatially extensive standardized surveys reveal widespread, multi-decadal increase in east antarctic Adélie penguin populations
Résumé
Seabirds are considered to be useful and practical indicators of the state of marine ecosystems
because they integrate across changes in the lower trophic levels and the physical
environment. Signals from this key group of species can indicate broad scale impacts or
response to environmental change. Recent studies of penguin populations, the most commonly
abundant Antarctic seabirds in the west Antarctic Peninsula and western Ross Sea,
have demonstrated that physical changes in Antarctic marine environments have profound
effects on biota at high trophic levels. Large populations of the circumpolar-breeding Adélie
penguin occur in East Antarctica, but direct, standardized population data across much of
this vast coastline have been more limited than in other Antarctic regions. We combine
extensive new population survey data, new population estimation methods, and re-interpreted
historical survey data to assess decadal-scale change in East Antarctic Adélie penguin
breeding populations. We show that, in contrast to the west Antarctic Peninsula and
western Ross Sea where breeding populations have decreased or shown variable trends
over the last 30 years, East Antarctic regional populations have almost doubled in abundance
since the 1980’s and have been increasing since the earliest counts in the 1960’s.
The population changes are associated with five-year lagged changes in the physical environment,
suggesting that the changing environment impacts primarily on the pre-breeding
age classes. East Antarctic marine ecosystems have been subject to a number of changes
over the last 50 years which may have influenced Adélie penguin population growth, including
decadal-scale climate variation, an inferred mid-20th century sea-ice contraction, and
early-to-mid 20th century exploitation of fish and whale populations.