Natural forces that have shaped this landscape include dominant south to southeast winds and tropical weather systems.  The estuaries of Anahuac National Wildlife Refuge are an important nursery for the fish and shellfish species found in the Gulf of Mexico.  Beyond the estuaries, the saltwater marshes ease inland.  Fresh water from an occasional storm and the inflow from rivers and creeks helps the keep saltwater out of the freshwater marshes, as well as providing nutrients and sediments.  With the change in salinity level comes a different plant community.  

Prior to human settlement, naturally-occurring wildfires and grazing by buffalo were key factors influencing native plan communities, particularly in the prairie grasslands.  Though remnant stands of native prairie can be found on the refuge, almost all of the region's historic native coastal tallgrass prairie has been lost.  These small but remaining areas play a vital role to many species that call the refuge home, from insects to migrating birds.  

A distinguishing feature of the region is the 'Cheniers,' ancient ridges made up of sand and shell fragments that generally run parallel to the Gulf and often found at the mouth of rivers, ancient alluvial deposits.  The higher cheniers support woody vegetation and many, over time, have served as protective barriers isolating wetlands from the Gulf and creating highly productive and diverse freshwater habitats.  These wooded areas are not only a source of fresh water for resident wildlife, they are very important for migrating birds in search of shelter and food.