Why an Ecotone is not a Mangrove

By Gilberto Cintron, US Fish & Wildlife Service
An ecotone is usually a transitional feature [without permanent “identity” (it is like a mixing zone)], whereas mangroves are stable entities (have a persistent identity) . Let’s say that when you see a mangrove ecosystem what you see is really a mosaic of features. Like elements in a picture, each little tile is part of the whole picture. If you focus your attention on a single tile you lose the whole picture. To see a mangrove as a whole you need to “step back” and see the whole, not the individual elements.

There are flows of materials between elements so that although they seem discrete they are tied to each other. In the case of mangroves, some of these elements can change their character and flip into other states, like the pixels on your computer screen. So the mosaic is dynamic, but the whole remains stable–it is still a mangrove ecosystem.

Really, the problem is in our need to fragment things. We cannot study an ecosystem broken into components. It cannot be assembled into a whole. I call this the Humpty Dumpty Effect –[Humpty Dumpty had a great fall. All the king’s horses and all the king’s men couldn’t put Humpty Dumpty together again”……… ] This nursery rhyme enfolds a very important management lesson. We cannot successfully manage ecosystems or landscapes in a fragmented way. Whereas scientists tend to like tearing things apart to see how they work, it is the manager’s role to do the opposite. Managers must learn to integrate. The problem is that in nature the parts in isolation behave in different ways than when they are part of a whole. So it is not an easy job to go from parts to whole.

One approach is to identify the larger whole and manage it to conserve all of its parts. This is called the First Rule of Tinkering….. Aldo Leopold said: “Instead of learning more and more about less and less, we must learn more and more about the whole biotic landcape [Round River 1953].

In the case of mangroves that whole is the tidal wetland that forms at the interface between the non-tidal upland to the lowest parts of the emergent sloping, tidally influenced platform. We call it mangrove, but that is because sometimes it has the woody trees we call mangroves. Other times the trees are missing and we call it a mud flat. If the trees are missing but the surface is covered by herbaceous vegetation we call it a salt marsh. If the herbaceous vegetation is missing there will probably be an algal mat that dries out periodically. We then call it a salt flat. But……it is always the same wetland. It is a natural engine to process sunlight and tidal energy and convert it into energy of higher quality (organic matter). Really, that platform is host to all those “types” of wetlands that exist on it in a latent form! Although the engines we know are mechanical, this tidal engine is adaptive, thus it adapts itself to local environmental conditions by changing its parts. Then we step in and confuse the issue by calling it different names!