Ecologists: Byron bypass not so good for Mitchell’s Rainforest Snail

A bulldozer clears Malleleuca trees on the eastern side of Butler Street to make way for the Byron bypass. Image: Paul Bibby

Dr David Newell & David Milledge

The opinion piece by Councillor Michael Lyon (4 December) on the Mitchell’s Rainforest Snail population in the vicinity of the Byron bypass development demonstrates a lack of understanding of basic ecological principles and of the statutory provisions of State and Commonwealth legislation protecting biodiversity. It also contains a number of factual errors.

The estimated number of individual snails and the assumed area of habitat are not the important issues here. It is the quality of habitat and the capacity of snail populations to persist in these areas that is crucial.

Habitat inequality

Much of the area being identified as suitable snail habitat in the vicinity of the Bypass, encompassing the Cumbebin Swamp, is sub-optimum habitat as stated by Council’s principal ecological consultants on a number of occasions. However, the area being impacted by the Bypass includes optimum snail habitat, as shown by recent surveys. Consequently, it is invalid to compare this with a larger area containing less suitable habitat.

It is the periphery of Cumbebin Swamp that is acknowledged as important habitat for the snail, evinced by numerous records including those about dwellings in the Lilli Pilli area. The latter records indicate the species has some refugial persistence, but such areas are far from secure and with the accelerating impacts of droughts and heatwaves resulting from climate change, these areas will be under greatly increased pressure.

Mitchell’s Rainforest Snail is classified as ‘a species that cannot withstand further loss’, again pointed out by Council’s principal ecological consultants. This means that loss of habitat, particularly optimum habitat, would be contributing to its extinction.

The species is listed as Endangered under the NSW Biodiversity Conservation Act 2016 and Critically Endangered under the Commonwealth’s Environment Protection and Biodiversity Conservation Act 1999. These listings should not be treated lightly, as Councillor Lyon appears to have decided.

Councillor Lyon refers to Dr Stephanie Clark as Council’s expert snail consultant in this matter, but Dr Clark does not appear to have conducted any field investigations in the Cumbebin Swamp area prior to this project. It is also understood that she was only given minimal time to prepare her review. He also claims that Dr Jonathon Parkyn’s PhD thesis was relied on ‘throughout the bypass approvals for biobanking and the environmental impact statements’ but Dr Parkyn’s thesis is not referenced in the environmental impact study (EIS) or the Biobanking Biodiversity Assessment Report.

Councillor Lyon is incorrect to refer to a Broken Head population of 500 snails, as this threatened population is located at Suffolk Park and there are no known records from the Nightcap Range. Some of the other populations he refers to, such as in the Kingscliff/Cudgen area are also under major development pressures.

The Critically Endangered Mitchells Rainforest Snail found on the margins of the Cumbebin Wetlands, where the Bypass is proposed. Image supplied.

Vegetation removal

What Councillor Lyon did not mention is that Council has just resolved to ‘prioritise the removal of vegetation and maintenance of vegetation within the rail corridor’ and endorsed the ‘unanimous support by the Northern River(s) Joint Organisation for the prioritisation of removing vegetation from within the rail corridor and the request to the state government for its immediate removal’. Unfortunately, this is likely to include much of the area and habitat that Councillor Lyon describes as where the snails and snail micro-habitat will be relocated to. Further, relocation offers little benefit to conservation of the Mitchell’s Rainforest Snail as it is an accepted scientific principle that most of such attempts fail, and any relocated ‘micro-habitat’ will quickly be subsumed into the existing habitat. 

Councillor Lyon’s concern over delays in constructing the bypass would probably have been alleviated if Byron Council had referred the potential impacts on Matters of National Significance (under the EPBC Act 1999), including the impact on the Mitchell’s Rainforest Snail, as part of the original assessment for the bypass, and not have been forced to do this retrospectively.

Dr David Newell is a senior lecturer at Southern Cross University and has co-authored three publications regarding the conservation and ecology of Mitchell’s Rainforest Snails and he also supervised Dr Parkyn’s PhD thesis.

David Milledge is a local terrestrial ecologist who has been involved with surveys of the Mitchell’s Rainforest Snail in Byron and Tweed Shires over the past 20 years. Both authors have worked as Byron Shire ecologists in past years.

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