Too Few to Survive

The Allee effect

An interactive lesson with 6 steps, about 5 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• The Allee effect: below a threshold A, per-capita growth turns negative.
• N = A is an unstable tipping point between recovery and extinction.
• Harvesting raises the tipping point; above the peak growth, no steady state survives.

Steps

1. Safety in numbers
2. Below the line
3. Either side of the tipping point
4. Growth at 600
5. How much can we take?
6. The passenger pigeon