Text Box: Introduced herbivores can also have devastating effects on native ecosystems. They compete with local species for food, often pushing them to the brink of extinction. A large number of herbivores are introduced intentionally as food or game animals. Sheep, rabbits and cows, as well as other livestock, are introduced in gargantuan numbers into areas that cannot support them, while game animals such as deer have in the past been released into wild areas either to entertain or feed settlers. Probably one of the introduced species most people know about; but least considered to be a threat to biodiversity, is the sheep - and when one mentions sheep one cannot escape mentioning New Zealand. Although somewhat off topic, it is worth noting that New Zealand's mind bogglingly large flock is responsible for 90% of the country's greenhouse gas emission; namely in the form of methane. (http://www.woolisbaad.com/environment.asp) However, these large concentrations of ungulates (hoofed mammals) has also had massive impact on the soil. Not only do they eat the soil-retaining plants, but their hoofs also weaken the topsoil. This leads to erosion, soil degradation and, through overgrazing, desertification. While New Zealand is a classic example, other countries, such as Karoo (in South Africa), are also feeling the far-reaching effects of overgrazing, not only on the ecosystem, but also on the economy. (http://www.woolisbaad.com/environment.asp) Another country battered by introduced herbivores is Australia. Originally a British colony, it suffered the introduction of many species of livestock to feed its settlers. Two of its worst introduced herbivores are rabbits and goats. Goats compete with native species such as the rock-wallaby. They kill trees by stripping their bark and eating their leaves, as well as consume the vegetation local grazers require: they have even pushed a species of Hibiscus (the Phillip island Hibiscus) to virtual extinction. This is without mentioning their potential to transmit diseases from the wilderness to domestic livestock or vice versa. (http://preview.thinkquest.org/03oct /00128/en/goats/effect_light.htm) Rabbits on the, other hand, are not ungulates but their incessant consumption of grasses, as well as their usage of warrens constructed by native marsupials have had numerous effects. For example, the prolific rabbit has forced the bilby and the borrowing bettong to regional extinction, as well as contributing to overgrazing and desertification. (http://rubens.anu.edu.au/ student.projects/rabbits/Impact.html)

Text Box: Edited by Keshal Patel on December 1st  

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