Invasive Species

Activities to try

1. 1

   Introduce a species: a population-dynamics simulation

   Why it works: The damage an invasive causes is not because it is 'evil' or inherently superior; the main mechanism this simulation shows is that nothing in the new place keeps it in check and native species never evolved defences against it, with competition and specific advantages like disease adding to the harm in particular cases. Human introduction and the resulting harm are what define 'invasive', distinct from natural range expansion.

   1. Start with a balanced native ecosystem shown with live population meters for the native species.
   2. Drop in a non-native animal and watch what happens to the meters over time.
   3. Toggle whether the predators and parasites that controlled the newcomer in its home range are present or absent, and compare the two outcomes.
   4. Predict before each run whether native populations will crash or settle, then check against the meters.
   5. State in your own words why native populations crashed in the simulation runs where the invader's home predators were absent.
2. 2

   Red vs grey: paired native/invasive comparison

   Why it works: Invasives cause specific, identifiable harms (competition, disease, unchecked predation) to native species — 'a new animal arrived' is not the whole story; the harm is the defining feature.

   1. Study a before/after picture of a native community, then the same community after an invasive is added, with arrows showing native populations declining.
   2. Fill in a paired comparison card for red squirrel vs grey squirrel, listing the specific harms: competition for food and squirrelpox disease (deadly to reds, not to greys).
   3. Add at least one more canonical case and its impact, choosing from: cane toads poisoning Australian predators, European rabbits devastating Australian vegetation, lionfish in the Atlantic, or Burmese pythons in the Everglades.
   4. Explain, for each case, whether the harm comes mainly from competition, disease, lack of predators, or predation on natives that lack defences.
3. 3

   Sort and match: native, non-native, invasive

   Why it works: Invasive is a precise category: non-native AND introduced by humans AND causing harm; a native pest is not invasive, and a species naturally extending its range is not automatically invasive.

   1. Sort a set of species into three categories: native, non-native but harmless, and invasive (non-native, human-introduced, and causing harm).
   2. Match each invasive species to its main impact (e.g. grey squirrel → squirrelpox and competition; cane toad → poisoning predators).
   3. Decide for each scenario whether it describes a human introduction or a natural range expansion, and justify the choice.
   4. Answer: a bird slowly spreads north on its own as the climate warms — is that invasive? Explain why or why not.