The deserts surrounding Chihuahua will be tropical and lush in the future, but re-hydrated deserts take time to recover from their past, and this takes decades, not years or months, to fully flower. Deserts do more than bake hard, they lack bacteria and humus by which to support plant life. Baked hard, without water, much of the land is lifeless, and without soil or wetlands to capture rain, the runoff scours the land clean so soil or humus is often lost, not gained, in the early years. Eventually, pockets of wetlands develop, soil accumulating, in areas where rapid runoff cannot occur. This can be assisted by man, survivors, by creating rock and gravel dams, holding back the runoff. Eventually, migrating fauna and flora arrive, and populate the wetlands and inland ponds, and the transformation to a sub-tropical land picks up the pace. During the shift itself, those living in and around Chihuahua will find their greatest worry to be resident from more populace area, Mexico City, who learn at the last minute of the predictions for their area, and flee their neighboring volcano, going north. These migrants will be unlikely to remain in what they consider a desert area, but will push forward, toward the US, toward lands they recall hearing about from family and friends working in the US. Thus, it will be travelers, not settlers, that will be the greatest worry for survivors in Chihuahua.
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