Mangroves: Edge Ecosystems

Edge ecosystems are often among the most diverse, since they combine two or more environments. They usually punch well above their weight and are crucial to the larger ecosystem they join.

Among the richest of these sorts of ecosystems are mangrove forests. Mangroves are amphibious trees that grow between high and low tide. They are sensitive to frost. In the U.S., they grow only in south Florida, and a few places in Louisiana so we went to see some in the Florida Keys.

You can see in my pictures how & why they do the jobs. The tangle of roots and branches help hold soil and protect the coast from erosion and storms. They also provide cover for fish and other wildlife to breed.

There are dozens of species of mangrove in parts of the tropics, but in Florida there are only three: black, red and white. Red mangroves grow in the inter-tidal region where their roots are always under water, even at low tide. If you see a clump of mangroves in the water at low tide, they are red mangroves. Black mangroves’ roots are under water during high tide, but exposed during low tide. White mangroves grow above high tide, but in places where their roots are always wet.

The keys, BTW, are are the end of a chain of barrier islands the stretch all the way from Canada. Barrier Island are interesting ecosystems with or w/o mangroves. A barrier island is temporary thing. They are more than sandbars but less than real terra-firma. In an instant of geological time, they are born and disappear and they are always moving. Storms play a big role in determining what grows on barrier islands. Most of the vegetation is small because storms blow down bigger trees. Where some hardwoods can establish, they are called hammocks. These are not big trees as we would expect inland, but they are forests.

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