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Prickly Pears in Australia
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Prickly Pears in Australia
Opuntia ficus-indica
Introduction
The Prickly Pear (Opuntia ficus-indica) is a species of true cactus native to the Americas. Through human action, it has since been introduced to other places around the world.
Introduction
Introduction into Australia - When and Why
The Prickly Pear was introduced to Australia in 1788 as a part of the First Fleet. They were broguht over to act as the host plant for cochineal insects used for dye. They quickly became a widespread invasive species, leaving over 40,000 square kilmeters of farmland unusable.
Introduction to Australia - when and why
Impact
After the Prickly Pear was introduced, it spread rapidly across the country, invading millions of hectares of farmland and rendering it unusable.
When growing, the cactus will take up a vast amount of space, leading to significant habitat loss for any native species attempting to nest, feed and survive.
Favourable Selective Pressures
Selection Pressures
Prickly Pears were able to invade Australia so succesfully for a number of reasons. The seeds of the cactus are tough and able to pass through the digestive system of birds and propegate. Its also an arid species, making it well suited for rural Australia. The seeds of the plant are easily detached from the parent plant by wind or floodwater, which is why its thought that the flood of 1893 spread the seeds to many new areas.
Biological control
The Prickly Pears control finally came in the 1920's, only after millions of hectares of land had been infested by them. Finally, a solution was found in the form of the moth Cactoblastis cactorum. An Argentinian species, it's diet consisted of the Prickly Pear genus. They were carefully cultivated, then released in gigantic quantities between 1927 and 1931. They saw a vast success, and by 1933 the Prickly Pear had cleared from over 7 million hectares.
Initial Artifical Selective Pressures.
Selection Pressures
Many control measures were implimented before a success. In the early stages, methods such as digging up and burning were used. Chemical eradication was used for a short while, but it became too expensive, toxic and dangerous, and a chemical shortage after WW1 reduced the process. Avenues for commercial use was considered, but nothing was secured.
References and Reliability
Reliability and Resources
References
- Wikipedia Contributors (2019). Opuntia. [online] Wikipedia. Available at: https://en.wikipedia.org/wiki/Opuntia.
- Wikipedia Contributors (2019). Prickly pears in Australia. [online] Wikipedia. Available at: https://en.wikipedia.org/wiki/Prickly_pears_in_Australia.
-National Museum of Australia; Lawson Crescent, A.P. (2022). National Museum of Australia - Prickly pear eradication. [online] www.nma.gov.au. Available at: https://www.nma.gov.au/defining-moments/resources/prickly-pear-eradication.
- Queensland Government, https://www.daf.qld.gov.au/__data/assets/pdf_file/0014/55301/prickly-pear-story.pdf
Reliability
Source 1
June 22, mccnmatt (2016). A prickly invasion. [online] The People & Environment Blog. Available at: https://pateblog.nma.gov.au/2016/06/16/a-prickly-invasion/.
The article, A Prickly Pear Invasion, was written by Catriona Donnelly, and provides a link to find more information about her. The sites information matches up with every other source I've found on the subject and provides sources.
Source 2
https://www.daf.qld.gov.au/__data/assets/pdf_file/0014/55301/prickly-pear-story.pdf
This source doesn't provide much information at all, other than that it was authored by the Queensland Government. However, the information provided matches up with other sources.