By the time the native americans arrived, approximately 15,000 years ago, the general geography of the Mid-South was set. The uplands were elevated to their present form, the Coastal Plain was fully developed and modern stream watersheds were established. And as the last ice age draws to a close, the sea level began to rise. During the last glacial period, large amounts of the earth’s water were sitting on the poles in the form of ice, so much that the sea level was 450 feet lower and the Coastal Plain extended perhaps 60 miles further out into the Gulf of Mexico. As the glacial ice melted, the sea level rose and the outer Coastal Plain began to shrink. With the rising sea level, the erosion that had been deepening Alabama river valleys declined, and the valleys began filling and broadening. The rivers meandered back and forth across the valley floors, depositing the present low floodplains and carving the bluffs of the lower terraces.
By 5,000 years ago, the appearance of the coastline becomes familiar as the sea level assumed its modern level and the modern barrier islands and spits became established.1 The Alabama and Tombigbee Rivers filled the upper half of Mobile Bay with silt and clay to form the Mobile-Tensaw Delta. The landscape is easily recognizable as Alabama. Though cosmetic changes continue into [End Page 219] modern times,2 from this point, time-traveling historians armed with topographic maps could easily find their way around the region in minute detail, making modern maps a reliable tool for reconstructing the late prehistoric and historic landscape.3
However, the plant cover of the state has profoundly changed in modern times, requiring careful consideration as we attempt to reconstruct events of the historic era. In general, the modern biological landscape is a poor guide to its prehistoric and early historic appearance.
Factors Regarding Forest Cover
In the South, almost any bare spot left untended will grow up in trees. The growth of a new forest typically progresses through predictable stages – herbs, grass, shrubs, mixed pines and hardwoods, and pure hardwoods. Provided the cycle is free of natural disaster, this will result in an old-growth hardwood forest, which can maintain itself indefinitely. This familiar biological principle, bare field succession, plays out on a human time scale of a couple of hundred years. Since we can actually watch bare fields grow up into hardwood forests, this leads to the assumption that prehistoric America must have been covered in old growth forest. This persistent idea, however, is not what the early travelers described.
Succession does not always run its full course. In some areas, a combination of physical, chemical, and biological happenstance will maintain the landscape at one of the successional stages for extended periods of time. What in theory should be a uniformly forested [End Page 220] landscape may in fact manifest itself as a mosaic of hardwood forest, grassland prairies, canebrakes, scrub, cedar glades, mixed forest, or longleaf pine.
An important landscape principle to remember is that practically no area of Alabama has escaped agriculture and/or timber clearing. By Depression times, essentially all of the Alabama landscape had been cleared for agriculture, grazing or forestry. Some old growth areas, particularly in the lowlands, temporarily survived, only to fall to the advent of mechanized logging after World War Two. Today, even areas covered with large hardwoods rarely contain trees more than 80–100 years old. Forested areas of Moundville Archaeological Park are shown on 1930s aerial photos to be covered in broomsage and sapling loblolly pine trees. By the mid-1990s, those pine trees, grown large, had died a natural death and been replaced by large fast-growing hardwood species. It will take another hundred years for succession to replace them with the slow-growing hardwoods species that comprise the mature forest. Bottom Line: Unless we have intentionally traveled to one of a handful of specific small areas, none of us has ever seen Alabama old growth of any kind.
Fire is one of the most active agents of this mosaic...