English: A aspect of a NASA attempt to "map out Sahara desertification in the Sahel sub-Saharan savanna was time. If land is not considered desertified unless the change is permanent, you need to track change over a long period—ten to twenty years at least—to see if vegetation is permanently altered. In 2006, Goddard’s Global Inventory Modeling and Mapping Studies (GIMMS) group, led by Tucker, released a twenty-four-year-long data set, the longest satellite-based vegetation record available. “The data set provides an essential 24-year record of vegetation dynamics that enables us to detect areas where degradation is taking place and areas of desertification,”...
El lloc web de la NASA disposa d'un gran nombre d'imatges de l'Agència Espacial Russa, o soviètica, i d'altres agències no nord-americanes. Aquestes imatges no són necessàriament en el domini públic.
{{Information |Description={{en|1=A aspect of a NASA atteppt to "map out desertification in the Sahel was time. If land is not considered desertified unless the change is permanent, you need to track change over a long period—ten to twenty years at leas
Aquest fitxer conté informació addicional, probablement afegida per la càmera digital o l'escàner utilitzat per a crear-lo o digitalitzar-lo. Si s'ha modificat posteriorment, alguns detalls poden no reflectir les dades reals del fitxer modificat.