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.

Sanctuary Mountain

We had an awesome day today up at sanctuary Mountain (Maungatautari). There was so much to learn and we were all really inspired to value and protect our endemic (native to NZ) plants and animals. It was fascinating learning about just how complex the journey is to saving our unique forests and wildlife.

Here are a few of the insights:

• 90% of the bush in New Zealand is endemic (only found in NZ).

Habitat loss

• We have lost 77% of the forest we used to have in NZ (see picture).
• We have lost 90% of the wetlands we used to have.
• A lot of the loss was due to deliberate burning with fire. The other main cause was introduced animals such as pigs, goats, cows, and possums.

Pests (Animals that are in the wrong place)

• Main pests include rabbits, possums, stoats, rats, cats, and weasels.
• For every 20 kiwi babies born 17 are killed by stoats.
• Rabbits were bought in to the country for hunting but their numbers got out of control. They considered bringing in foxes to get rid of them but decided on stoats. 
• The kiwi population is still in decline. The population is being reduced by 2% a year. That works out to be about 40 kiwi dying each week.

The Maungatautari project

• Biggest project of its kind in NZ.
• The exclusion fence cost 15 million dollars to make. 
• 47 km long.
• $6000 per day to run the project.

Tuatara (we managed to see a couple of these)

• This ancient animal predates Gondwana and the dinosaurs.
• It has unique body features - 3 eyes (one gets covered in scales when young), 2 sets of eyelids (for protection), no ear holes (but does have ear drums).
• 95% of the population are on one island. Efforts are being made to move some to another location in case of disasters such as a disease outbreak.

Takahe (the Sanctuary has 3 of these rare birds.)

• Can weigh up to 3.5 kg.
• Were thought to be extinct but have since been found.
• Flightless birds.

Swimming to survive!

We had an awesome final swimming session where the focus was water survival. The students had the scenario of a sinking ship and experienced swimming in clothing, removing clothing in water, putting on life jackets in water, learning how to survive as a group in cold water, as well as other survival skills. One thing the students have learnt that we hope they never have to use.

The students also got to have a hydroslide which was a fun way to finish the terms lessons.