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How to Introduce a Species to an Ecosystem

Introducing a new species into an existing ecosystem can be a risky business. The new species is unlikely to be kept under the same control in its new environment that it would be through the biological equilibrium of its native ecosystem and may therefore start to affect its new ecosystem for the worse. Its new prey, for example, will not have an adapted defense to counteract its method of attack, or maybe it will have no predators to prevent its numbers from getting out of hand. Only under certain circumstances should a non-indigenous species be translocated to a new ecosystem.

Instructions

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  The government of a country must carry out a risk assessment of the potentially harmful consequences of introducing a non-indigenous species to an area. Apart from the irrevocable damage an invasive species can cause to native organisms within its new environment, the economic cost to the people of the country in attempting to repair that damage must also be considered.
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  An accepted introduction of a non-indigenous species is a measure of biological control to target natural prey that itself was introduced at an earlier time. This prey has since become invasive and a cause of harm to the environment. A specific example of this is the arrival in Europe of Aphalara itadori, a Japanese bug, to prey on the pervasive Japanese Knotweed. The expectation of a specialist eater preying outside its evaluated target prey is very low. From more than 400 worldwide alien releases introduced to quell the growth of invasive weeds in the past 110 years, only nine have been noted to have caused damage to native species.
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  In some cases a species is introduced to an area very similar to its indigenous environment, where it theoretically might once have thrived. It is less likely to impact the natural balance of the existing ecosystem if its natural food source is also found in its new environment. This type of introduction might be a worthwhile attempt to re-establish a species whose numbers have plummeted in its native ecosystem due to the affect of invasive species. The kakapo parrot, for example, has been brought back from near extinction through transfer from its native New Zealand to nearby islands free of rats and ferrets.
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  Reintroducing once-native species, while still highly debatable and controversial, is usually seen as a means of restoring an ecosystem to its full working glory or as a reaction to a failing ecosystem. An increase in conservation attitudes toward the end of the 20th century led to the reintroduction of many large bird and mammal species to their former homelands. The California condor and the Mexican gray wolf both have captive breeding programs behind them, which have enabled them a gradual reintroduction to their historic ranges.

Nature