Pull One Thread, the Whole Web Moves

You'll learnto trace how removing or adding one species ripples through a connected web.

An ecosystem is a web of who eats whom and who depends on whom, which is why a disruption rarely stays where it lands. Pull out a keystone and the change runs down the levels; drop in a newcomer that left its predators behind and it runs away with the place; press with habitat loss or a warming climate and the effect travels the same links. Through all of it, energy still makes one pass. Eleven short steps; press Next for each one.

11 STEPS · 6 QUICK CHECKS · A WEB, NOT A STACK · CASCADES RUN OUTWARD · INVADERS LOSE THEIR CHECKS · ENERGY IS ONE-WAY · v5

pull one thread and the whole web moves

Before you start

What you're looking at

A kelp-forest web of six species — kelp, urchin, snail, fish, crab and otter — joined by grey feeding links.

The question

Pull one species out of a web like this, and does the effect stay local or spread?

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