For each site in Trek Birmingham, you’ll see we identify its ecoregion. An ecoregion is part of a mapping system based not on cities and counties, but on ecology. Plants and animals don’t pay much attention to human boundaries – a tree doesn’t know if it’s Alabama or Georgia and a bird flits easily across state or county lines — but biologists rely on maps to document species distribution, so they use to ecoregions to show where plants and animals can be found.
Although most commonly used by scientists, the ecoregion concept can help us all understand the landscape in which we live, work and play.
Ecoregions point out patterns in the landscape that determine not just where plants and animals make their homes, but where we do, too. That’s especially the case in Birmingham, where the region’s initial growth was spurred by nearby natural resources for industry and the proximity to rich farmlands to feed its population.
Ecoregions are sorted into four levels, from the very large to the detailed. Each marks a geographic area with a shared climate, geology, topography and similar water and soil throughout. When those things are the same, the ecosystems found there will look alike, too.
Each ecoregion gets a roman numeral depending on its size. In Level I, all of North America, from the Maine coast to the Louisiana swamps to the California desert, is divided into just 15 ecological regions. Each level then has more divisions, culminating in several hundred Level IV ecoregions.
Alabama has 29 Level IV ecoregions, which is one of the reasons the state has such rich biodiversity and can claim more species than any other state east of the Mississippi River. At level III, where Alabama has six, they align with the physiographic regions used by geologists, another demonstration of how geology shapes our state’s terrain.
Curious how Birmingham’s ecoregions vary?
Here in the Birmingham metropolitan area, there are two Level III ecoregions: the Ridge and Valley and the Southwest Appalachians. This is how they break down:
The Ridge and Valley (Level III) Ecoregion
is made up of parallel ridges and valleys formed by geological folding and faulting. The ridges and valleys come in a variety of widths, heights and stone, including limestone, dolomite, shale, siltstone, sandstone, chert and mudstone. About half of the region is covered with forests; there are plenty of springs and caves; and the streams and rivers support a huge number of fish and other animals. The Ridge and Valley Ecoregion has three Level IV ecoregions within it in our area:
The Southern Limestone/Dolomite Valleys and Low Rolling Hills Ecoregion
which we’ll call the Limestone Valleys and Hills – is mostly broad valleys and rounded hills with many caves and springs. There are forests of oak and pine or oak and hickory, plus agricultural, industrial and urban lands.
The Southern Shale Valleys Ecoregion
also consists of broad valleys, but with fewer, smaller hills mainly dominated by shale. The soils here tend to be deep, acidic, moderately well-drained and slowly permeable. Many of the steeper slopes are used for pasture or have gone back to forest.
The Southern Sandstone Ridges Ecoregion
is mostly sandstone but also has shale, siltstone and conglomerate. The ridges are steep and forested with stony, sandy soils that aren’t very fertile. Elsewhere, most of the ridges are narrow, but in Alabama, the Coosa and Cahaba ridges are broader. A good example of how the sandstone bedrock affects the look of the ecoregion can be found at Moss Rock Preserve.
The Southwestern Appalachians (Level III) Ecoregion
stretches from Alabama north to Kentucky as a patchwork of forests, woodlands and croplands over low mountains. Here, the planet’s crust was forced steeply upwards when the continents collided to form the Appalachian Mountains. This region includes some of Alabama’s most dramatic mountain scenery, including Sand Mountain, Lookout Mountain and the Jackson County Mountains. Within it, there is one level IV ecoregion in our area:
The Shale Hills Ecoregion
also called the Warrior Coal Field – which covers most of Walker County to the west of Birmingham — has the lowest elevation in the Southwest Appalachians but is still very hilly. The bedrock is mostly shale, silt and sandstone that are hard for water to flow through, making for smaller streams. The land is mostly forested, but extensive coal mining has left open-pit mines that have changed the landscape.
To read more about ecoregions, go to the Environmental Protection Agency’s map here.