The Adélie penguin has a circum-Antarctic distribution and is widely considered a useful indicator of status and change in the Antarctic and Southern Ocean ecosystems. Breeding distribution of the Adélie penguin was surveyed with Landsat-7 Enhanced Thematic Mapper Plus (ETM+) over the entire continent of Antarctica. An algorithm was designed to minimize radiometric noise and to retrieve Adélie penguin colony location and spatial extent from the ETM+ data. In all, 259 ETM+ scenes were selected from the Lansdat archive from the 1999–2003 era and were used in the retrieval. Pixel clustering identified a total of 244 individual Adélie penguin colonies, ranging in size from a single pixel (900 m2) to a maximum of 875 pixels (0.788 km2). The Landsat retrievals successfully located Adélie penguin colonies that accounted for ≈96 to 97% of the regional population used as ground truth, with errors of omission and commission on the order of only 1 to 2%.

Distribution of Landsat-7 ETM+ scenes over the continent of Antarctica that were used in the retrieval of Adélie penguin distribution and abundance (top), and the location of Adélie penguin colonies retrieved from the satellite data (bottom).
The continent-wide Landsat survey identified 26 colonies previously unknown and unreported in the literature. In addition, regional analysis found several areas where the Landsat retrievals indicate populations that are significantly larger than published estimates. The principal results of this are illustrated in the figure, and can be visualized by using Google Earth. A kmz formatted file containing geographic overlays of colony images retrieved from Landsat 7 data (along with colony spatial area and other information) can be obtained at this URL: http://tinyurl.com/kmjh4tb.

Antarctica remains one of the planet’s most challenging environments for biological survey. Satellite remote sensing represents a significant improvement over direct field counts alone, which lack the scalability of remote sensing surveys, and are subject to underestimation bias in regional or global estimates due to the remoteness and inaccessibility of sections of the Antarctic coastline. Landsat retrieval of Adélie penguin distribution and abundance has radically expanded the opportunities for regular, high-quality biological surveys at the continental scale. As a result, Antarctica has become a model system for the use of remote sensing for biological conservation.

This work was done by Mathew Schwaller of Goddard Space Flight Center, Heather Lynch of Stony Brook University, and Colin Southwell and Louise Emerson of the Australian Antarctic Division. For more information, access doi:10.1016/j.rse.2013.08.009, doi:10.1371/journal.pone.0113301. GSC-17019-1