The Importance of Keystone Species

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A keystone is the topmost stone in a stone arch. It is under less pressure than its neighbours but, should it be removed, the arch will collapse. There are animal species called ‘keystone species’ as, if they should become extinct or numerically so small that they cannot perform their function, it could mean the collapse of an ecosystem. Keystone species have a a vital role to play in their environment: a pivotal role that it is out of all proportion to their numbers. Should they disappear, the effect on their region would be devastating, affecting the wellbeing and very existence of many other species in the area. Keystone species are not necessarily apex predators but they might consume or hold in check another species which would otherwise dominate the local environment. A distinguishing feature is that it prevents lower level species from monopolising, say, food or habitat to the detriment of others. An example is the prairie dog. Its system of tunnels helps prevent run off and erosion when it rains. It reverses the compaction of the soil caused by grazing cattle. Burrowing owls and mountain plovers use the tunnels as nesting areas. Should the prairie dog vanish, all these other species would be affected. The cassowary and mountain tapir consume seeds of many different types. As they travel through their habitat, the seeds are dispersed in their faeces and later germinate. In the case of the cassowary, some seeds will not germinate at all unless they pass through the digestive system of the bird. Some 200 different plant species have been found in the bird's stomach. Its short digestive tract and rapid rate of digestion even allows it to eat toxic plants. I am continually amazed by Mother Nature. Imagine a seed not germinating at all unless swallowed then excreted by a cassowary! I've adapted this from a Bubblews discussion.