Trophic Cascades

“Changing a predator can travel through several levels and alter plants, habitat, and physical processes.”

01 / PLAINLY

What it means, plainly

A trophic cascade is a chain of indirect effects traveling across levels of a food web.

02 / CONTEXT

A little more

Predators may reduce prey or change prey behavior, thereby affecting lower consumers and producers. Strength and direction vary with omnivory, productivity, refuge, and web structure.

03 / WHY IT MATTERS

Why it matters

It shows why removing or restoring one species can create consequences beyond its immediate diet.

04 / EXAMPLE

A familiar example

Sea otters reduce kelp-eating urchins; under certain conditions, their presence helps sustain kelp forests.

05 / LIMIT

What it does not mean

Not every three-level chain produces a strong cascade, and ecosystems do not all respond alike to predators.

06 / NOTICE

Notice it in your day

Build a web with predator, herbivore, and plant; add an omnivore and predict how it complicates the result.

FINAL NOTE

The idea worth keeping

Measure abundance, behavior, and producers across several links before claiming a cascade.

QUESTIONS / 02

Questions people still have

Do cascades always run from the top down?

No. Resources and productivity also create bottom-up effects, and both directions can interact.

Can behavior create a trophic cascade?

Yes, if induced behavior changes other levels; a predator need not kill many prey.