Biological Diversity Mapping Comes of Age

Over the past 60 years, Earth observing has evolved from aerial photographic studies to high-tech airborne 3-D imaging and global satellite-based monitoring. These technological advances have been driven by an increasing call for quantitative and information-rich data on changes in Earth properties and processes. Within the biospheric remote sensing arena, focus has mostly been placed on changes in land cover and land use, ecological disturbance including fire, and basic biophysical properties such as vegetation light absorption and greenness. In recent years, however, interest has rapidly increased in the area of biological diversity monitoring. This special issue of Remote Sensing [1] captures some of the latest thinking on how both traditional and newer mapping technologies can contribute to biodiversity monitoring and analysis. The term biodiversity encompasses variation in the composition and functioning of life at scales ranging from genes to entire biomes. This special issue captures a critically important portion of this range. First, there has been an explosion of work at the " organismic " level with remote sensing. Large-area mapping and analysis of plant species was once considered highly unlikely; now we see a rolling out of methods and applications that bring the possibility to life. Several of the papers in the special issue report on the use of Light Detection and Ranging (LiDAR) and/or imaging spectroscopy (also known as hyperspectral remote sensing) for organismic remote sensing. LiDAR provides a quantitative, three-dimensional view of the vegetation, revealing the height of canopies, their branching and foliar distribution, and other properties. New LiDAR results indicate a fast expanding capability to detect and map species and communities, often with high precision and accuracy. While LiDAR presents options for analyzing biodiversity via canopy structure, imaging spectroscopy provides an avenue for looking at plants through their detailed reflectance properties or " spectral traits ". In all plant canopies, spectral traits are determined by a combination of factors ranging in scale from the amount of foliage present (i.e., leaf area index) to the angular distribution of the foliage, and to the chemical composition of the leaves. Papers represented in the special issue repeatedly highlight the enormous leverage afforded by imaging spectroscopy for understanding species composition based on their often unique spectral traits. Several papers took organismic remote sensing to its current limits, by combining the structure and spectral properties derived from LiDAR OPEN ACCESS