The Web of Life (22-5) Keystones


The food web is but one facet of the biotic web between species. Widely varying in significance, a vast variety of interactions between species take place, ranging from incidentally indirect to studiously conscientious.

There no apportioning consequence. However ancillary an interaction may seem, its import may ripple throughout an ecosystem. We simply cannot know the impact of disturbing Nature until long after the damage is done, perhaps irreversibly so (via self-organized criticality).


Living things exist in a fine balance. ~ English microbiologist John Postgate

Ecological networks are both fragile and robust in their facets and dynamics. That dichotomy spans an emerging understanding about the intricate workings of ecosystems.

A keystone species is one that has a disproportionately large effect on the health of a biome. Keystone species play a vital role in creating and maintaining an ecological community. The contributions of keystone species are not always obvious.

Plants are commonly creators of ecosystems. A few animals shape their habitat to the benefit of other species. Even parasites can sprinkle ecological benefits where they would not otherwise appear.

Seed-dispersing animals are integral to the health of the forest ecosystems where they live. Large herbivores, such as elephants and rhinos, are especially essential.

Smaller herbivores are less productive to plants, as seeds either are spit out in the same place or do not survive chewing or digestion. Tapirs defecate 8% of the seeds they eat, while elephants drop 75%, along with copious fertilizer. 65% of elephant-deposited seeds germinate.

Megaherbivores act as the ‘gardeners’ of humid tropical forests. They are vital to forest regeneration and maintain its structure and biodiversity. ~ ecologist Ahimsa Campos-Arceiz

Microbes, plants, and animals affect the lives of others in a variety of ways. Ecological interactions of all kinds form an interdependent web.

The addition or loss of particular species and the alteration of key interactions can lead to the disassembly of the entire interaction web. ~ Mariano Rodriguez-Cabal et al