Previously I discussed the importance of protecting species "low on the food chain" in order to maintain the high numbers of top predators and large herbivores from an ecological standpoint. However, ecosystem protection can work from other directions as well. In the salt marshes of Cape Cod, for example, overfishing of striped bass and blue crabs has led to a population explosion of herbivorous crabs and snails, which devour the marsh grass. With no predators to keep their numbers down, the herbivores' population increases beyond its natural limit. This has gotten to the point that scientists are considering artificially stocking the salt marshes with blue crabs and striped bass.
Removing predators can be just as problematic to an ecosystem as removing prey species, but unfortunately people such as fishermen who make a living by taking animals from the wild do not usually see the full ecological implications of what they do. In fact, many of the most popular food fish today--including tuna, salmon, seabass and swordfish--are top predators.
In salt marshes like this one, ecosystems are in danger of collapsing due to the decline of top predators.
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