Prospects and pitfalls for spectroscopic remote sensing of biodiversity at the global scale

Abstract

Imaging spectroscopy is a powerful new approach for observing aspects of the biological diversity of the Earth, conveying information about plant functional traits, habitat, and plant diversity itself. For decades, spectroscopic data suitable for this application have mainly been collected by aircraft. But in the next decade, global coverage from space by high-quality spectroscopic data will become available, preceded by instruments providing “global access”-not wall-to-wall coverage but data from almost anywhere in the world. For decades, scientists have experimented with and discussed optimal strategies for collecting spectroscopic data, but the next set of missions is now sufficiently well-defined that ecologists should consider how best to use the data that can now be expected. The anticipated flood of data will provide a new window on diversity, characterizing it in new ways that comprehensively sample space and change over time. Spectroscopic data will be peta-scale or larger, perhaps as much as 10 TB per day, and the data themselves will be high dimensional, requiring and allowing advanced big data techniques to be fully exploited. These data raise specific challenges such as how to characterize aggregate ecosystem characteristics, since the traits observed will change with phenology. Pixels will be fixed at ~30 m, 10-106 times larger than the plants they sample; other instrument objectives are likely in the range of 10 nm spectral sampling, coverage from 400 to 2500 nm with signal to noise in the range of 250-400. Imaging spectroscopy from space represents a huge opportunity for global ecology, but many conceptual, algorithmic, and theoretical issues will challenge the users.