Undoing Ecological Messes is Costly

More than a decade ago, some New Zealanders imported brush-tail possums from Australia to establish a fur trade. Longer ago, rats got to Kiwi land with settlers. Stoats (weasels) were introduced to control European rabbits that had earlier been introduced. European deer were introduced by hunters. Humans distorted ecological relationships that they did not understand.


The possums ate leaves and denuded forests. The rats killed ground- nesting birds and ate their eggs among other impacts. The stoats killed endemic birds, reptiles and insects, exterminating some. The iconic flightless Kiwi is threatened by invaders brought willfully to New Zealand. The deer population grew so large that their numbers controlled the rate of growth of erosional soil gullies. Many control programs have been initiated to try to control these introduced predators and pests. Some have been successful on islands but not on the mainland.


Trying to control these introduced species now costs the New Zealand national government nearly US$50 million per year. Thoughtless species introductions either by private citizens, hunters and fishers or by government agencies disrupts ecosystems and wastes precious conservation funds.


More information: Nicolai Toki, Threatened Species Ambassador, Department of Conservation, Wellington, New Zealand

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