Controlling Invasive Species (Cambridge (CIE) A Level Biology): Revision Note

Controlling invasive species

• A species that has moved into an ecosystem where it was previously unknown is an invasive species

• An invasive species can occur naturally as a result of a species migrating or expanding their habitat but most recorded incidents of invasive species have been caused by humans

• In the past humans have:

  • Knowingly collected and traded species between countries via ships

  • Unknowingly provided transport for invasive species to a new ecosystem

  • Introduced alien species deliberately as biological control for pests

Problems with invasive alien species

• The biological process of evolution often brings balance to an ecosystem

• Through evolution the environment a species lives in strongly influences the adaptations that the species evolve to live in that environment

• A non-native invasive species will have evolved adaptations for survival in different environmental conditions so when they are introduced into the new ecosystem this can upset the balance

• In a new ecosystem invasive species will have few or none of the natural population controls that existed in their previous ecosystem:

  • They will have no natural predators or competitors

• As a result they are able to increase in number at a rapid rate

• This can affect the processes within an ecosystem

  • Competition may occur between invasive species and native species that occupy a similar niche with the native species getting displaced or pushed to extinction. It could be competition for things such as prey, soil nutrients, light and space

  • Many invasive species can be over successful predators causing a massive decline in their prey species

  • Invasive species can introduce new diseases, to which the native species have no natural immunity

  • The biodiversity of an ecosystem is impacted which reduces its productivity

• Humans can also feel the knock-on effects of an invasive species taking over an ecosystem

  • The spread of novel diseases and irritants of the skin / breathing system directly affect human health

  • The economy of a country can be severely impacted by the costs of trying to control invasive species and their negative effects

  • In the past travel has been brought to a standstill by invasive species, with some plant species prone to blocking up waterways