Eighty Years of Committees as Cane Toads March On

Filed under Environment & Pollution, News ~ by Throsby on  11 Feb 2019

The House Standing Committee on the Environment and Energy will hold a public hearing tomorrow for its inquiry into controlling the spread of cane toads.

The Committee will convene two roundtable-style sessions involving scientists and groups involved in controlling cane toads.

The inquiry is focused on how cane toads can be controlled and additional support that could be provided.

A further public hearing is planned for next Wednesday 20 February 2019. Details will be announced in due course.

Public hearing programs, submissions received and further information can be found on the inquiry website at www.aph.gov.au/canetoad.

Public hearing details: 10.00am – 11.30am (Canberra time), Wednesday 13 February 2019, Committee Room 2R2, Parliament House

An audio broadcast of the public hearing can be accessed at https://www.aph.gov.au/News_and_Events/Watch_Parliament.

Throsby’s Two Cents

Throsby wonders if the cost of cane toads and their toll on our environment will ever be recouped by the sale of sugar, especially considering its historic low price and export competition from a litany of international sugar-producing countries.

Native to South and mainland Middle America, Cane toads were introduced to Australia from Hawaii in June 1935 by the Bureau of Sugar Experiment Stations, now the Sugar Research Australia, in an attempt to control the native grey-backed cane beetle and French’s beetle. These beetles are native to Australia and they are detrimental to sugar cane crops.

Adult cane beetles eat the crop’s leaves, but the main problem is the larvae, which feed on the roots. Adult cane beetles have a heavy exoskeleton and their eggs and larva are often buried underground, making them difficult to exterminate. Furthermore, conventional methods of pest control, such as pesticide use, would eradicate harmless species of insects as well, making it an unsatisfactory method.

The cane toads bred immediately in captivity, and by August 1935 more than 102 young toads were released in areas around Cairns, Gordonvale and Innisfail in northern Queensland. More toads were released around Ingham, Ayr, Mackay and Bundaberg. Releases were temporarily limited because of environmental concerns but resumed in other areas after September 1936.

Since their release, toads have rapidly multiplied in population and now number over 200 million and have been known to spread diseases affecting local biodiversity. Unfortunately, the introduction of the toads has not only caused large environmental detriment, but there is no evidence that they have affected the cane beetles that they were introduced to prey upon.

The toads have steadily expanded their range through Queensland, reaching the border with New South Wales in 1978 and the Northern Territory in 1984. The toads on the western frontier of their advance have evolved larger legs; this is thought to be related to their ability to travel farther. As a consequence of their longer legs, larger bodies, and faster movement, about 10% of the leading edge cane toads have also developed arthritis.

It was estimated that cane toads migrate at an average of 40 kilometres (25 miles) per year as of 1994, but new research in 2014 indicated that the migration rate had increased to 60 km per year on the western front.

The long-term effects of toads on the Australian environment are difficult to determine, however some effects include "the depletion of native species that die eating cane toads; the poisoning of pets and humans; depletion of native fauna preyed on by cane toads; and reduced prey populations for native insectivores, such as skinks."

Precipitous declines in populations of the northern quoll have been observed after toads have invaded an area. There are a number of reports of declines in goanna and snake populations after the arrival of toads.

Below: Source: Kearney, M, Phillips, BL, Tracy, CR, Christian, KA, Betts, G & Porter, WP 2008, ‘Modelling species distributions without using species distributions: the cane toad in Australia under current and future climates’, Ecography, vol. 31, pp. 423–434

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