Land cover mapping and data availability in critical terrestrial ecoregions: A global perspective with Landsat thematic mapper and enhanced thematic mapper plus data

Land cover provides objective and multi scale information on the extent and conditions of habitats both currently and retrospectively. Over four decades since the launch of the first land-observation satellite Landsat-1 in 1972, a tremendous number of earth observation images have been acquired and archived. Here we examined land cover mapping in 142 critical terrestrial ecoregions (identified by WWF Global 200) from three aspects: Landsat Thematic Mapper and Enhanced Thematic Mapper Plus (TM/ETM+) data availability, literature and existing global land cover map. We found that: (1) the availability of Landsat TM/ETM+ for historical land-cover change analysis in those ecoregions is poor. Only 17 ecoregions and 38 ecoregions have sufficient number of seasonal images in the Landsat archive for change analysis at 10-year and 5-year intervals, respectively. (2) Only 26 of 142 ecoregions belong to research hotspots of land cover mapping based on a spatialized literature database. (3) From a 30 m global land cover map (which is FROM-GLC, Finer Resolution Observation and Monitoring - Global Land Cover), only 28 ecoregions have greater than 80% map accuracy while 36 ecoregions have poorer than 50% map accuracy. Our finding suggests a significant gap of observation and understanding of these critical ecoregions from space, and an urgent need to meet the requirement of the conservation science community, in order for land cover data to fulfil its potential to timely monitor the loss of biodiversity from space, improve our knowledge of the state of conservation, and inform better decision making. (C) 2015 Elsevier Ltd. All rights reserved.