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Pests and Weeds

Plant pests

Weed invasion is a common problem in urban and urban-edge areas, with many weeds species coming from people’s back yards. Weeds pose a great threat to stream health by restricting the natural process of native regeneration by competing with native plants for light, nutrients and space. They are very good competitors and can quickly take over an area forming a monoculture (single species). A mixture of native vegetation is important for reducing erosion, providing shade, providing habitat and a source of detritus (a food source for many stream dwelling creatures), and forming the basis of a natural ecosystem. Disposing of weeds and other garden plants responsibly helps reduce re-invasion into natural and restored stream areas.

Animal pests

Animal pests can eat seeds, seedlings and saplings and can cause canopy destruction. They also eat native birds, their eggs and young, and can severely reduce lizard and invertebrate numbers. 

Why have pests had such an impact?

New Zealand evolved without the presence of land mammals, other than three native bat species. Native birds evolving in this same environment didn’t need the ability to fly well and instead developed other ways to avoid being hunted. Mammals were introduced to New Zealand by humans and they have severely impacted our flora and fauna due to their hunting styles, excellent sense of smell, and lack of natural controls such as predators of their own. Animal pests have decimated large areas of indigenous forest and reduced (and sometimes made extinct) mainland populations of birds, reptiles, insects and plants. Many species now only survive on pest free offshore or "mainland" islands. Any control of animal pests should be undertaken in conjunction with a weed control programme. A combined pest and weed control effort will increase the success of the restoration and natural regeneration of an ecosystem.

More information on plant and animal pests.