Riparian habitats are of particular ecological importance in the predominately dry landscape of the American Southwest. Riparian vegetation generally occurs in drainage systems with more persistent or predictable water sources at or near the surface, compared to surrounding lands. Riparian areas provide important corridors for flora and fauna of the region. For instance, riparian corridors provide important migratory and breeding habitats for birds, many of which use this habitat exclusively. However, riparian environments are also common pathways for the spread of invasive plant species.