Migration and Global Environmental Change

This project generated estimates of net migration (NM) by ecosystem over the four decades from 1970 to 2010. Because of the lack of globally consistent data on migration, indirect estimation methods were used. We relied on a combination of data on spatial population distribution for five time slices (1970, 1980, 1990, 2000 and 2010) and subnational rates of natural increase in order to derive estimates of NM on a 30 arc-second (~1 km) grid cell basis, which were then summed by ecosystem. We ran 13 geospatial NM estimation models based on outputs from the same number of imputation runs for urban and rural rates of natural increase. We took the average and standard deviation of the runs to produce the results described in the ‘Results’ section and Appendix A (see Maps A1–A4 for maps of the results by decade).

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