In the “backyard” of the Panama Canal

After 10 days of ship travel, at last we reached the entrance to the Panama Canal and our passage to the Atlantic Ocean and Caribbean. It took almost 12 hours to transit the 50 miles of the canal, through three sets of locks on the Pacific side, into huge Lake Gatun, and then through three sets of locks on the Atlantic side.

We began our journey through the Canal at 6 a.m., just as the sun was coming up.
A couple of female Frigate birds flew over to check us out. These are soaring specialists that cruise the oceans looking for fish and squid, and often steal a meal from other birds (like Boobies). They may follow large ships (i.e., frigates) which often scare up fish in their wake.
The Bridge of the Americas (which goes into Panama City) looms over the entry to the Canal. This is the main entry to both the new Panamax (super large ship canal) and the two older, original canals.

I was particularly interested in getting a look at the islands in Lake Gatun, which was formed by damming the Chagras River at a narrow point near its mouth on the Atlantic side (see map below near Gatun locks) back in 1913. When dammed, the river then flooded a once wide valley forming a large lake with just the mountain tops projecting up forming a series of small and large islands in the lake.

One of the largest islands, Barro Colorado (circled in black on the map), was set aside as a nature reserve in 1923 and has been administered by the Smithsonian since then. With almost 100 years of climate and biological data, it is one of the most studied tropical forest systems in the world.
Small lakes on the sides of the main part of the canal serve as reservoirs for circulating water through the locks.
Drainage systems collect rainwater from the surrounding hills to channel it into the main waterway. Vegetation along the banks of the canal is sparse to allow water runoff, while the hills behind are more mature rainforest.
Larger islands in Lake Gatun have undisturbed tropical rainforest with an amazing biodiversity of plants and animals. The first census in 1982 recorded over 300 tree species in a 100 acre plot on Barro Colorado Island!

This area of Panama receives about 100 inches (i.e., 8 feet!) of rain annually, but almost all comes during the rainy season. During the dry season between December and April, less than 3 inches of rain falls and many of the island streams dry up. The soil becomes so dry, large cracks develop in it. Flowers and insects disappear, trees stop producing fruit, and animals on the island become food limited.

As a result of changes in the forest structure with limited island land surface and the size of the islands themselves, species diversity of animals, and especially birds, is markedly lower than that of intact rainforest on the hillsides of the canal — as you would expect. Researchers have found smaller numbers of under-story bird and mammal species, and there are no large mammalian carnivores to control the herbivore populations. But food is a limiting factor here.

Islands (really hilltops) in Lake Gatun dot the lake surface. It spans 164 square miles in all, and makes up about 20 miles of the length of the waterway from the Pacific to the Atlantic.
Black Vultures soared over the hilltops of some of the islands in the far distance.
Plants growing on top of plants all the way down to the water’s edge — that’s tropical diversity! Imagine trying to hack your way through this forest from one end of an island to the other…

National Geographic produced an interesting video featuring some of the work that has been done on Barro Colorado Island in 2007: Panama Wild — Rainforest of Life. If you like nature videos and want to know more about this area of the world — click on the video below.

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.