Adelie Populations Growing

By Paul Homewood

h/t Richard Treadgold

Richard has unearthed a more recent study of the population of Adelie penguins, published in January 2017:

Abstract

Antarctica and the Southern Ocean are increasingly affected by fisheries, climate change and human presence. Antarctic seabirds are vulnerable to all these threats because they depend on terrestrial and marine environments to breed and forage. We assess the current distribution and total abundance of Adélie penguins in East Antarctica and find there are 3.5 (95% CI 2.9–4.2) million individuals of breeding age along the East Antarctic coastline and 5.9 (4.2–7.7) million individuals foraging in the adjacent ocean after the breeding season. One third of the breeding population numbering over 1 million individuals breed within 10 km of research stations, highlighting the potential for human activities to impact Adélie penguin populations despite their current high abundance. The 16 Antarctic Specially Protected Areas currently designated in East Antarctica offer protection to breeding populations close to stations in four of six regional populations. The East Antarctic breeding population consumes an average of 193 500 tonnes of krill and 18 800 tonnes of fish during a breeding season, with consumption peaking at the end of the breeding season. These findings can inform future conservation management decisions in the terrestrial environment under the Protocol on Environmental Protection to develop a systematic network of protected areas, and in the marine environment under the Convention for the Conservation of Antarctic Marine Living Resources to allow the consumption needs of Adélie penguins to be taken into account when setting fishery catch limits. Extending this work to other penguin, flying seabird, seal and whale species is a priority for conservation management in Antarctica and the Southern Ocean.

http://ift.tt/2yKKGB7

This builds on results of the 2014 study by Lynch and LaRue, which I referred to yesterday here.

The new study comes up with a figure of 3.5 million in East Antarctica. In comparison, Lynch and LaRue estimated 3.79 for all of Antarctica, including 21% on the Peninsula.

The Southwell paper surmises that the difference may be due to the unavailability of satellite imagery and lack of recent direct counts for a number of East Antarctic breeding sites in Lynch and LaRue’s global assessment.

It is worth reiterating what the Lynch study stated:

Our global total abundance of 3.79 million breeding pairs is 53% larger than the most recent estimate of 2.47 million breeding pairs 20 yr ago (Woehler 1993). This difference of ∼1.3 million breeding pairs can be explained largely by increasing abundance at known colonies (27% of the difference) and abundance estimates of colonies that had not been previously surveyed (explaining 32% of the difference)….

In addition to a genuine increase in the size of known colonies, the increase reflected in our census is, in part, an artifact of estimating abundance at colonies that had never been surveyed before. In fact, mapping abundance and distribution for the largest and most remote Adélie Penguin colonies is one of the major advantages of using high-resolution satellite imagery. Indeed, our finding is similar to the recent global estimate of Emperor Penguins (Aptenodytes forsteri) using satellite imagery (Fretwell et al. 2012) that found nearly double the number of Emperor Penguins expected on the basis of previous estimates, as well as breeding populations previously unknown to science.

In short:

Part of the increase since 1993 in population is real
Part is due to under measurement in the past.

They also noted that:

LaRue et al. (2013) found that a colony on Beaufort Island, in the southern Ross Sea, grew by 84% in response to glacial retreat and increased habitat availability. We hypothesize that some colonies may be experiencing habitat release where climate changes have caused glacial retreat (LaRue et al. 2013).

All in all, Adelies seem to be doing just fine.