Trophic cascades

Flowing out of our trip to Sanctuary Mountain on Friday we took a further look at how fragile and interconnected ecosystems are. If you change one aspect of an ecosystem it can have dramatic unseen long-term effects.

We discussed the food chain and how destroying one species will affect the animals further up the chain. However, we then looked at what happens if you eliminate the species at the top of the food chain. Is there any effect?

We watched the below two videos on Trophic Cascades. How an animal at the top of the food chain plays a significant role in holding the rest of the ecosystem together. One video looks at how reintroducing wolves into Yellowstone National Park had a dramatic effect on the wildlife, plant and tree growth, and even the path of the rivers. The other video looks at how whales play an integral part in stirring up the ocean, fertilizing the upper level of water, and making it possible for plankton to absorb carbon from our air.



We then looked at how introducing new species can have dramatic effects on an environment, such as what happened in NZ when rabbits were introduced:

1. Rabbits were introduced for sport (hunting).
2. Rabbit population got out of control.
3. Farms destroyed by rabbits.
4. Stoats introduced to deal with rabbit problem.
5. Stoat population got out of control.
6. Stoats became the predators of native birds.
7. Native birds became endangered or extinct.

This all helped us realise just how fragile and perfectly interconnected our natural environment is. We need to be very careful when making decisions about removing or introducing species and plants from an ecosystem.