A cruise on the Delta

Five rivers feed into the 200,000+ acres of wetlands that make up the second largest river delta system in the U.S. just north of Mobile Bay in southern Alabama. The Mobile-Tensaw delta’s expanse of swamp, bog, natural rice paddies, canals, and rivers makes this area of Alabama a real biodiversity hotspot where you can find more species of fish, turtles, snails, crayfish, and oak trees than anywhere else in North America. Harvard ecologist E.O. Wilson has called it North America’s Amazon, and so it was a real treat to venture out on a small boat to explore some of the smaller waterways of the delta for ourselves.

Wild rice and Phragmites reeds grow along the edges of the river, almost closing off the small waterways in the labyrinth of corridors throughout the delta.
A variety of snails colonize the floating vegetation in the swampy bogs.
Clumps of rice seed fell into the bottom of the boat as we passed through narrow canals. A Yellow Warbler might not be interested in the seed, but there are plenty of insects in this vegetation.
We must look carefully on the river banks before stepping out of the boat — there are plenty of alligators in the delta waters.
Cruising up the Tensaw river we entered a cypress swamp where the trees grow right in the water, completely independent of any land surface.
Cypress forests are a haven for all kinds of birds — small migratory warblers as well as large waders like a Great Blue Heron.
In the Spring, these waterways are lined with brilliant flowers.
Spanish moss hangs from the Cypress’ lower branches, and odd vertical stumps arise from the tree’s roots. Their function is not certain, but they might assist in collecting more sediment to buttress the tree roots in the soft, muddy river bottom.
Honeybee nests can be found where large branches have broken away from the trunk. This is a “honey” tree.
Not only is there great diversity of vertebrate animals in the delta, but there are hundreds of species of insects as well. And some are really big — like the praying mantis..
and this 4-inch lubber grasshopper (which is not fully mature yet).

The southeastern U.S., and the Mobile delta in particular, was a refuge for species driven south during the ice ages of the Pleistocene glaciation. Warm temperatures year-round and plenty of rainfall (averaging 70 inches per year) ensure the most equitable conditions for life to survive, and so it has in this cradle of biodiversity.

5 thoughts on “A cruise on the Delta

    • I think the phragmites is native there, and has an important role in flood control. This is an amazing area to visit — it was nothing like I imagined, and was so much more diverse than I had realized. You think you are in the tropics.

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