南极帝企鹅种群栖息地动态变化遥感分析

帝企鹅是南极生态的指示器,其种群栖息地分布变化对研究南极气候具有重要意义,但传统的人工实地调查难以获取全面、准确的种群栖息地信息。本文依据帝企鹅种群排泄物在卫星影像上的蓝、红波段和近红外与短波红外波段的反射率差异,提出2种可以有效判别种群排泄物的光谱指数（NDII、EI）,据此精确识别帝企鹅种群排泄物并确定其种群栖息地位置。根据2009年195景时相合适、质量较好的Landsat 7 ETM+卫星影像,获取了南极共计38个帝企鹅种群栖息地,其中新发现7处（Bowman Island , Dibble Glacier , Auster, Point Geologie , Cape Crozier , Brownson Islands和Rupert Coast）,消失2处（Amundsen Bay 和Ledda Bay）,另外25处（除Thuston Glacier, Luitpold, Sanae, Gould, Ragnhild和Beaufort Island外）位置未发生明显变化,实现了全南极帝企鹅种群栖息地的识别与定位。种群栖息地提取的正确率为94%,提取结果受限于影像质量和种群规模,且随着种群规模的提高,该方法的提取效果也越好。帝企鹅种群栖息地的分布与气候要素息息相关,种群栖息地往往倾向于气温较低和海冰密集度较高的区域,气候变化对每个种群栖息地的影响不同,因此气候与种群栖息地变化的具体关系需要长时间、区域性的观测进行研究。随着气温持续上升和海冰密集度的变化,南纬70°以北的种群栖息地面临较大的威胁,帝企鹅种群呈现向极点逐渐收缩的趋势。

Analysis of Antarctic Emperor Penguins Colonies Changes Based on Remote Sensing

Emperor penguin is the indicator of Antarctic ecosystems. The distribution of its colonies owns essential significance for the study of Antarctic climate. Emperor penguins are sensitive to changes of the sea ice concentration and distribution. Thus, they have become an essential species for investigation on the effect of climate changes on the Antarctic ecosystems. However, it is difficult for the traditional manual investigation to obtain comprehensive and accurate information of the population colonies. Although some researchers have devoted to find emperor penguin colonies using remote sensing imageries in recent years, but their methods require considerable human involvement and cannot be used to detect all colonies rapidly and effectively. Emperor penguins breed and rest on land-fast sea ice and live in the same area for about six months, leaving extensive yellowish brown faeces which are significantly different from the white ice and snow around them. Inspired by the normalized difference snow index (NDSI), which is used for delineating snow cover, we can establish a/some similar index(s) to extract the faeces from extensive snow cover. On the basis of the difference between the reflectance of the faeces produced by emperor penguin in blue and red band, near infrared and shortwave infrared bands, two spectral indexes (NDII, EI) are putted forward to effectively recognize the faeces produced by emperor penguins, and determine their colony locations. According to the 195 scenes appropriate and quality-good Landsat 7 ETM+ imagery in 2009, a total of 38 emperor penguins colonies are obtained, 7 colonies of which are newly discovered (Bowman Island, Dibble Glacier, Auster, Point Geologie, Cape Crozier, Brownson Islands and Rupert Coast), 2 colonies have disappeared (Amundsen Bay disappeared and Ledda Bay), and the positions of the other 25 colonies (except Thuston Glacier, Luitpold, Sanae, Gould, Ragnhild and Beaufort Island) do not change significantly. The overall accuracy of colony detection is about 94% and the performance of the colony detection is influenced by the data quality and colony size. The performance of this method improves with increasing colony population size. Although spectral attributes are chosen to identify faeces produced by emperor penguins, some misclassifications may happen. This method may miss a few small colonies of which the sizes are smaller than spatial resolution of the imagery. The failure of detecting these colonies of small size is most likely due to the mixing of non-colony terrain in the Landsat pixels. These smaller colonies may well be identified by the satellites that have higher pixel resolution, and this method can be adapted to other high spatial resolution of satellite data in the future. The distribution of emperor penguin colonies is closely related to the climatic factors, and colonies tend to gather at the regions where temperature is low and ice concentration is high. It is different for climate change occurring at different colonies. Long-time and regional observations are needed to study the relationship between climate and the changes to the distribution of colonies. With the continued rise of the air temperature and the change of ice concentration, the colonies of which the latitude are below 70 °S are facing greater threat, and emperor penguin population shows a trend to shrink to the southern pole.