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Threats to Ecology

A Precious Resource
Introduced Weeds and Fish

Ecology is all about living things. Living things can die if their environment is damaged. There are many events that can harm freshwater ecology.

Natural disasters

Mount Ruapehu is one of the most active volcanoes in the world. If there was a big eruption, the ash and other material from the volcano could spread through the air and get into local waterways. This material could pollute the rivers and lakes and kill the plants and animals that live there.

Storms and flooding could also affect the water in local waterways. Lots of silt could be carried into the rivers and lakes. Plants and animals in the water could find it hard to breathe and hunt for food if there is a lot of silt in the water.

Human impacts

Changing waterways

One of the biggest threats to freshwater ecology is from water being changed from its natural course to provide irrigation, water supply, and energy production.

Towns and cities - urbanisation

When it rains in urban areas, the rain that runs off buildings and down the gutters is called storm water run-off. Storm water run-off can carry pollution into the local waterways.

Special effort is made when planning new towns and housing areas so that we have good water quality.


Over the last fifty years, land and industrial development in the Taupō area has increased the amount of nitrogen in the water. Nitrogen makes algae grow faster, which makes the water murky. The health of Lake Taupō and its rivers, depends upon clean, clear water.


Over-fishing can lead to certain animals disappearing. This affects other animals who eat them and all the animals in the food web are affected. The health of a waterway can be measured by how many different things live there.

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Investigate: Find out if there are any threats to a waterway near you.

A volcanic eruption could pollute Taupō's waterways. Image: LEARNZ.

Changing water from its natural course can affect freshwater habitats. Image: LEARNZ.

In urban areas storm water run-off can carry pollution into local waterways. Image: LEARNZ.

Land development increases nitrogen in the water. Nitrogen makes algae grow faster. Image: The Bushland Trust.

This is a picture of illegally caught trout. Over-fishing can upset the food web. Image: DOC.

A Precious Resource
Introduced Weeds and Fish