Justification of Red List Category
This species is listed as Near Threatened because it is projected to undergo a moderately rapid population decline over the next three generations owing to the effects of projected climate change. However, it should be noted that there is considerable uncertainty over future climatic changes and how these will impact the species.
A survey of satellite images from 2009 found 46 colonies containing c.238,000 breeding pairs, suggesting a total of c.595,000 individuals (Fretwell et al. 2012). Since then, a further seven colonies have been discovered bringing the total number to 53 (Fretwell, pers. com.). The global population estimate has not yet been updated.
An analysis carried out by Ainley et al. (2010) suggests that all colonies north of 67-68°S could be lost when Earth's tropospheric temperature reaches 2°C above pre-industrial levels, with negative impacts on all colonies north of 70°S. In this study, 2042 is the median year (range 2025-2052) at which a 2°C warming is forecast to be exceeded by the four climate models used (those models used in the IPCC Fourth Assessment Report [AR4] that most closely predicted data collected on environmental conditions in the Southern Ocean over recent decades) (Ainley et al. 2010). An ensemble of these models was then used to predict changes in climate and habitat in the Southern Ocean until 2025-2052, namely sea ice extent, persistence, concentration and thickness, wind speeds, precipitation and air temperature. Predictions were then made based on historic responses of the species to past variations in environmental conditions (Ainley et al. 2010).
According to a survey of satellite images by Fretwell et al. (2012), the global population in 2009 is estimated at c.238,000 breeding pairs, including nine colonies north of 67°S, accounting for c.36,600 pairs. Assuming the loss of these colonies and an exponential population trend, BirdLife International has projected that a decline of c.27% in the number of breeding pairs will occur over the next 61 years (three generations). There are substantial uncertainties over future changes in the patterns of weather variables and how these are likely to impact the species, as well as whether there will be a lag in the decline of mature individuals as recruitment falls, or whether this decline will be proportional to the loss of colonies as climatic changes result in the increased mortality of mature individuals. The relocation of A. forsteri colonies will be limited by decreases in sea ice thickness, making it more difficult for them to find stable, long-lasting fast ice for breeding (Ainley et al. 2010). Colonies could conceivably move to any areas of coastline not affected by ridges formed by wind-blown pack ice; however, where this has occurred in the past it has been regarded as a rare event. Importantly, it has been argued that a simple latitudinal gradient in the loss of sea ice is unlikely, and that warming has so far been regional in the Antarctic (Zwally et al. 2002, Turner et al. 2009, Trathan et al. 2011, Fretwell et al. 2012). With these uncertainties in mind, a precautionary approach is taken, and the population is projected to decline by 20-29% over the next three generations.
Aptenodytes forsteri has a circumpolar range, restricted when breeding to the coast of Antarctica where breeding colonies occur right around the continent (Fretwell et al. 2012). At least ¾ of the breeding colonies of this species are vulnerable to predicted changes in sea ice conditions and 1/5 may be quasi-extinct by 2100 (Jenouvrier et al. 2014). There are regional variations in population declines but colonies located north of 70°S have a probability of 46% to decrease by up to >90% by the end of this century (Jenouvrier et al. 2014).
This species is marine and pelagic, feeding mainly on fish in Antarctic waters (although krill and cephalopods can be important dietary components). It breeds almost exclusively on fast ice near the coast or on the coast itself, sometimes up to as much as 200 km from the open sea. Only one known colony occurs wholly on land (Robertson et al. 2014) while a small number uses available land for parts of their breeding cycle. Four colonies are known to locate at least temporarily onto the top of ice shelves (Fretwell et al. 2014). It has an annual breeding cycle, arriving at colonies in late March to April, and lays eggs in May/ June. Chicks fledge in December/January (del Hoyo et al. 1992).
It is thought to be threatened by the effects of projected climate change, primarily through future decreases in sea ice concentration and thickness, as affected by wind speed and persistence, as well as changes in other climatic variables such as precipitation (Ainley et al. 2010). The decrease of a colony on Emperor Island from c.150 pairs in c.1970 to fewer than 20 pairs by 1999 (at which time it occurred on land), with the apparent disappearance of the colony by 2009, has been linked to a decline in seasonal sea ice duration, particularly in seasonal stable ice suitable for nesting (Trathan et al. 2011). Disturbance is a threat in some areas, with problems to colonies caused by the proximity of scientific bases and aircraft movements (del Hoyo et al. 1992).
In recent years, Antarctic sea ice increased, especially in East Antarctica. In June 2014, it had reached the largest extent on record with > 2 million km2 above the long term average. Increased runoff of fresh water from melting glaciers in West Antarctica and strengthening southerly winds in the Ross Sea region were suggested to decrease sea surface temperatures (Fan et al. 2014). Alternatively, increases in the wind strength of westerly winds may increase sea ice extent. However, Ferreira et al. (2015) indicated that this could be a short-term response only (~20 years) and that over the long-term effect will still be a decrease in sea ice extent.
The Antarctic cryosphere continues to change and with it the habitat of A. forsteri. In 1994-2003, the ice loss from ice shelves around the continent was estimated to occur at a rate of 25±64 km3/yr. From 2003 to 2012, ice loss had increased to 310±74 km3/yr; in West Antarctica, the fastest warming part of Antarctica, ice loss had increased by 70% (Paolo et al. 2015).
In the long-term, the habitat of A. forsteri is likely to deteriorate to a point where suitable habitat may be available only in restricted refugia or, in the worst case, may no longer be available (Jenouvrier et al. 2014).
Human impacts potentially also include disturbance from tourists, scientists, construction of new science facilities and fisheries, particularly fisheries for Antarctic krill. Fisheries for Antarctic silverfish could also develop in the future. Harvesting of silverfish and krill could be a threat, if management does not adequately take into account the needs of species that feed upon these species. Oil spills may also be important at local scales. Protection of habitat at sea is important, with the designation of appropriate protection for transit, foraging and rafting areas at sea.
Conservation Actions Underway
The species is the subject of on-going international research but there are currently no special conservation activities. Human disturbance is strictly regulated in some areas (Antarctic Specially Protected Areas).
Conservation Actions Proposed
Conduct regular surveys to monitor population trends. Continue to improve on existing modelling work to better predict future population changes. Carry out further research into the species' ecology to improve understanding of how environmental changes will affect the population. Continue to monitor the thickness, extent and persistence of Antarctic sea ice, and other environmental variables to assess the availability of suitable breeding habitat. Continue international work to tackle the drivers of projected climate change.
Text account compilers
Wienecke, B., Butchart, S., Trathan, P., Ekstrom, J., Taylor, J., Moreno, R., Calvert, R.
Fretwell, P., Schneider, T., Kooyman, G., Schmidt, A., DuBois, L., Makhado, A., Ainley, D., Wienecke, B., Ballard, G., Woehler, E., Trathan, P.
BirdLife International (2018) Species factsheet: Aptenodytes forsteri. Downloaded from http://www.birdlife.org on 22/10/2018. Recommended citation for factsheets for more than one species: BirdLife International (2018) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 22/10/2018.