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Invasive Species

Invasive species are non-native or non-indigenous species which have the ability to spread beyond their native range, increase in population size and cause potentially adverse effects. It is important to note that many non-native species found across various environments are not invasive because they lack the ability to increase in population size and spread rapidly.

In comparison to invasive species, non-native species being introduced into a new community are not necessarily a problem. For example, sometimes non-indigenous species are purposely introduced into a new community for agricultural reasons, such as to kill a pest.

Conversely, invasive species are an issue. For one, invasive species can cause fluctuations in community structure and thus, disrupt the functioning of the population. Secondly, invasive species can cause the extinction of native species. Extinction can result from the spread of diseases, competition or hybridization, to name a few possibilities.

In order for non-native species to become invasive they must first become established in a new community and then they must spread. Establishment involves three stages: arrival, survival and propagation. There is a lag time between the initial introduction and spread stages, with many of the new species which are introduced to new environments not surviving to spread their range.

Since only a small portion of introductions lead to spread, only the strongest non-native species become invasive. Some features that invasive species possess are the ability to adapt quickly, having few natural predators and having few natural diseases.

Invasive species are more common than one might think. For example, zebra mussels are invasive species found in North American waters such as Lake Simcoe. Their introduction is thought to have been conducted accidently by humans. Invasive species can become a huge problem and thus, focusing policy and research efforts on eliminating accidental introductions and learning eradication methods to prevent the spread of non-native species which may become invasive is critical. 



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