Figure: Landsat-7 image (courtesy of USGS/NASA) showing wetlands in the northern Central Valley, California.
There is a growing quantity of free imagery that can be extremely useful, for example in environmental projects. One such project, called BirdReturns, is using Landsat free satellite imagery to help migrating birds survive, supported by citizen science and conservation groups, assiting birds from Alaska and Canada to Central and South America, parallel to the Pacific coast.
In California, 90% of habitat previously available as a stopover for migrating birds has been lost to development and degradation. By analysing Landsat imagery for existing and potential habitats and comparing this to migratory routes, it has been possible to identify where resources can be used most cost-effectively in enhancing habitat that benefits the most birds and species, thus helping to reduce migratory loss.
Visit The Nature Conservancy website for further information.