Comparison of a regional-level habitat index derived from MERIS and MODIS estimates of canopy-absorbed photosynthetically active radiation

Abstract

Earth observation data and approaches are increasingly being utilized to improve our insights into the ecological processes that influence biological diversity. Physically based indices such as the fraction of absorbed photosynthetically active radiation (fAPAR) intercepted by vegetation are particularly useful in describing variations in productivity and seasonality that can, in turn, be related to species abundances and distributions. The increasing availability of time series of fAPAR data from 2000 from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensors, as well from other satellites, such as ENVISAT, has resulted in a motivation to extend techniques, originally developed for MODIS biophysical data, to other sensors. In this letter we investigate and demonstrate the application of the dynamic habitat index (DHI) methodology to the MEdium Resolution Imaging Spectrometer (MERIS) Global Vegetation Index (MGVI) across the over 1 million km2 province of Ontario, Canada. Results indicate the three DHI components varied significantly in their magnitude, principally because of MODIS fAPAR estimates being larger than those observed by MERIS fAPAR. However the relationship was, in general, temporally stable across the years and the residuals tended to be spatially consistent. We conclude that following inter-calibration the production of consistent indicators of habitat and biodiversity from different data sources is possible, thus supporting global terrestrial ecological research, policy support and management.