Read in data of Ramankutty dataset (Source: Ramankutty N, Foley JA, Norman J and McSweeney K (2002) The global distribution of cultivable lands: current patterns and sensitivity to possible climate change. Global Ecology and Biogeography, 11, 377-392.). Link to data: https://www.nelson.wisc.edu/sage/data-and-models/global-land-use/grid.php