Around the world, savannas are threatened by human actions like logging, development, conversion to agriculture, over-grazing by livestock, and introduction of non-native plant species.For example, in the drier parts of the African savanna, overgrazing by goats and cattle has removed most of the vegetation that holds the soil in place.And most of the southeastern United State's longleaf pine savannas have been affected by logging.This has created desert-like conditions.