Mosquitoes been bugging you this summer ? Stop those sleepless summer nights! Come hear Dr Cameron Webb, Medical Entomologist with the University of Sydney and Pathology Westmead Hospital, speaking on mozzies and mosquito-borne disease at the next Oatley Flora and Fauna Society meeting Feb 23rd (Mon) 7.45pm at Uniting Church Hall Fredrick St, Oatley. For more information on Dr Cameron Webb see his blog at http://cameronwebb.wordpress.com
Jim Vickery , OFF member and retired Environmental Engineer, spoke on this topic at the 27th Oct meeting. Jim is determined to capture as much life- giving rain falling on his roof as possible by storing it in water tanks around his home. This reduces his reliance on town water supply and the erosive impact of excess storm water on our local streams. He provided guidelines and graphs showing the relationship between tank size and roof area based on rainfall records. In drier times, the Reliable Draw[water drawn every day without emptying tank ] is between Average Summer and Dry Winter levels shown in this chart. It is a useful guide relating storage volume and roof catchment area. A 2000L tank provides 50 100 L/day [if catchment is 100 sqm or more], sufficient to supply a
toilet in a small household and some water for the garden. A 6000L tank needs at least 200 sqm of catchment to supply water to a washing machine, toilet, and garden. Techniques for the collection, storage and delivery of rainwater were reviewed along
with uses for the water that overflows the tank. Jim runs his excess water into a swale in his backyard providing a bog that can recharge the water table. Running excess into a pond is another excellent method of harvesting rain water.
Rainwater tank installation guidelines:
- Determine your daily need for rainwater.
- Determine the size of your available roof catchment area.
- A 2000 L tank will provide 50 to 100 L/day from a 100 sq m or larger roof.
- A 6000 L tank or larger is necessary for supplying a washing machine or something similar. If the roof catchment area is greater than 200 sq m then the tank is less likely to empty out during dry periods .
The Society has purchased a number of books which are available for loan to OFF members. Available at the back desk at Monday meetings.
Titles include :
- The Biggest Estate on Earth (Bill Gammage) – investigates the land management of Aborigines.
- A History of the Blue Labyrinth (Bruce Cameron) – a beautifully produced book with lots of photos and many references to our former Treasurer Harry Whaite
- Sustainable House (Michael Mobbs) – what one person has done to be self-sufficient in energy, water and waste disposal in his Sydney house.
- Sustainable Food (Michael Mobbs) – the sustainable use of water and energy associated with growing and processing food.
- A Natural for World Heritage (Geoff Mosley)- the argument for granting World Heritage Listing for Royal National Park. The Green Corridors of Southern Sydney (NPA Southern Sydney) – a DVD outlining the importance of protecting the green areas south of Sydney,
Ecosystem Guidelines for the Conservation of Aquatic Ecosystems of the Georges River Catchment: A Method Applicable to the Sydney Basin Click here for pdf of study
For waterway managers the conservation of freshwater streams in Australia is commonly
underpinned by comparing water quality data with default ANZECC water quality guidelines.
However distinctive conditions found within many streams of the Sydney basin render a number of the
default guidelines not suitableand prone to misinterpretation. In this study we draw on a three year
monitoring program and follow the framework recommended by the ANZECC guideline to develop
a catchment specific approach for the conservation of aquatic ecosystems for the Georges River
catchment. In addition to the ‘common’ set of water quality guidelines we include values for a
selection of ionic parameters and guideline values for aquatic macroinvertebrate communities, riparian
vegetation condition and catchment imperviousness. The study revealed three distinct
patterns of ecosystem disturbance and water quality characteristics that corresponded to the level of development across the catchment from reference forested areas through to highly urbanised centres.When compared to non-urban reference sites streams with greater than 5% impervious surfaces showed
emergent signs of ecosystem degradation while those with >19% imperviousness had highly degraded
water quality, macroinvertebrate communities and riparian vegetation.Based on the results of this
study, we recommend two sets of regionally relevant ecosystem and water quality guidelines, one for
the conservation of streams with high ecological value that would apply to waterways with minimally
disturbed catchments and the other to apply to urban streams and stream restoration projects.
Although the focus of this paper is the Georges River catchment, the approach developed in this study
can be easily applied to other urban catchments within the Sydney Basin
The extent of catchment impervious surface is recognised to be an important factor associated with the condition of urban freshwater streams. We tested the hypothesis that the degree of catchment imperviousness predicted the relative ecological condition of freshwater reaches within the network of streams and rivers in the partly urbanised Georges River catchment in temperate south-eastern Australia. The 2-year study involved two spring and two autumn assessments of water quality (chemical and physical) and ecological condition, using benthic macroinvertebrates, riparian vegetation and calculation of catchment imperviousness. The study revealed that highly urbanised streams had strongly degraded water quality and macroinvertebrate communities, compared to clean non-urban reference streams. We found three clear groups of sites with varying degrees of ecological condition, being categorised according to the level of catchment effective imperviousness (low <5.0 %, moderate = 5.0–18.0 % and high >18.0 %). Water pollution also varied according to these categories. A combination of two water chemistry attributes (total nitrogen and calcium), along with catchment imperviousness and riparian vegetation condition, were identified as being the factors most strongly associated with variation of macroinvertebrate communities. Based on our results, we recommend that protection of the ecological condition of streams should focus on not only water quality but also include catchment imperviousness and riparian vegetation condition.
The geochemical signature of freshwater streams can be used to determine the extent and nature of modification to stream water geochemistry due to urban development. This approach used the Gibbs (1970) diagram as a model for evaluation of changes to ionic composition linked to urban development. In this multi-year study, the geochemistry of 21 waterways in the Georges River catchment, Sydney, were monitored and compared with the level of urban development as measured by sub-catchment imperviousness and directly connected imperviousness. The results reflect a strong relationship between the intensity of sub-catchment urban development and stream geochemistry. All major geochemical attributes increased with escalating levels of urban development. The largest increase was for bicarbonate, which increased 18 times from a mean of 6.4 mg L–1 at non-urban streams to a mean of 118 mg L–1 at urban streams. Similarly, mean concentrations of calcium increased by 14 times (from 2 to 27.9 mg L–1). Mean salinity was enriched in the most urban streams, compared with non-urban streams, by more than 6 times. We attribute this, in part, to the influence of urban geology, notably concrete stormwater infrastructure. Changes in stream geochemistry due to urban development are an important element of the urban stream syndrome.
Understanding the habitat requirements of breeding Powerful Owls (Ninox strenua) in Sydney is an important step in improving species management in urban areas. A Birdlife Australia project focusing on the population dynamics, breeding success and requirements of owls in the Greater Sydney Area is in its third year. In addition, the owls of the lower Georges River are under surveillance for a study led by Chris Lloyd, who is speaking to the Society in September this year.
For reasons that are still unknown, the breeding season in 2014 has been later than previous years, with many breeding pairs commencing nesting in July. Two breeding pairs in Oatley and surrounds are leading the charge, having laid eggs in June. In an achievement for the St George area, chicks from these owls have been heard at both sites, and seen in one. According to David Bain of Birdlife Australia, these are the first of the season.
The photograph is of the juvenile owl at one of the Oatley sites on the day after fledging.
Matt Mo, Bev Pedder and Peter Hayler 18 August 2014
REMINDER – Chris Lloyd will speak on the Changing ecology of the Georges River and Powerful Owls at next Oatley Flora and FAuna Soc. meeting on Monday 22 September.
On Monday 11 August OFF members attended a seminar on debunking myths on the economics of mining. Coal Mines and Gas fields are approved largely on the basis of the claims made about jobs and economic benefits. However, two speakers from The Australia Institute enlightened the audience on the fact 0f who benefits and who bears the costs of the mining industry in the NSW economy.
Two papers summarizing the information were distributed:
OFF obtained a copy of Mining The Age of Entitlement -
State governments are more usually associated with the provision of health, education and law enforcement than industry assistance. So it might surprise taxpayers to learn that state government assistance for the mineral and fossil fuel industries consumes significant amounts of their money. This paper details the value of state revenue that would otherwise have been available for increased vital public services – for example, more teachers, nurses and police.
by Richard Denniss, Roderick Campbell and Richard Denniss
Dr Tom Grant of UNSW spoke on this subject at the April 28th meeting, a research interest in which he has been involved for 40 years. Click here for details of his publication.
While the International Union for Conservation of Nature (ICUN) classifies the status of the platypus as a ’species of least concern’, he argued that it is more probable that it is vulnerable, due to its dependence on water in which to feed. Spread along eastern Australia from Cooktown and to Tasmania, more investigation is needed to determine the current platypus population. Large numbers were trapped and shot in the 19th century, and there are remaining threats to their continued conservation. They are no longer found in the streams of the Adelaide Hills, Mount Lofty Ranges, and Fleurieux Peninsula in South Australia, where they once occurred.
The Platypus is mobile, reclusive and active throughout the night but most often seen around dawn and dusk. The male has a poisonous spur that it may use in its defence, but is predominantly used against other males during the breeding season. Capture can be risky as they drown if caught and trapped underwater for too long. Radio-telemetry has been used to investigate platypus biology. When foraging, the platypus’s main sensory organ is its bill, much more sensitive than its eyes and ears that are closed when underwater. It has receptors that detect touch, pressure, and electric fields from its prey.
Because platypus populations can be small or spread along rivers, and many animals are mobile, population numbers are difficult to determine accurately. The Australian Platypus Conservancy encourages the public to report sightings of platypus as a way of determining population sizes at particular places. The Platypus is protected, but threats to survival include mortality in illegally set nets and traps, and habitat degradation. Natural and regulated high and low flows ofwater through rivers and creeks can damage nesting and feeding sites.Fossils of ancient forms of platypus have been found in central Australia, but during the time when these species existed the areas were wet, not arid as they are now. The platypus is found in most areas where it was prior to European occupation of Australia, but its populations are probably lower.
Extreme weather events resulting from climate change are likely to decrease the size and distribution of platypus populations. They depend on a stable supply of water, and droughts can reduce current, distribution and numbers. Floods have a detrimental effect on juvenile platypus survival. Foxes are predators and some populations in Tasmania have been prone to a potentially fatal fungal disease causing ulcers and lesions. Use of illegal fishing nets is also a serious problem, as Platypus need to surface regularly to breathe. http://www.platypus.asn.au & http://australianmuseum.net.au/Platypus
A scientific paper by Matthew Mo has been published in the prestigious journal Australian Zoologist. Matthew spoke to the Oatley Flora and Fauna Society in April 2011 and led a spotlighting walk for geckos in Mortdale Heights Park on 27 April 2012. The group observed 10 geckos on the rock walls and in crevices.
The Broad-tailed Gecko Phyllurus platurus is a saxicolous lizard occurring in the Sydney Basin including the Sydney Metropolitan Area. A search of desktop records confirms that populations remain across the region, including in the central business district and in long-established suburbs. This paper reports on habitat selection derived from a population study carried out in a reserve of remnant bushland in the St George district. Open walls and the underside of overhangs were the most frequently exploited structures used by P. platurus. Geckos were found typically no higher than 2.5 m from the ground. The mean density of P. platurus had a negative relationship with available rock surface area. Geckos retaining original tails dominated the sample size, which is in contrast to previous work on museum specimens. Diurnal surveying was trialled, during which some P. platurus were detected on the outer edges of crevices. Survey results expand baseline information and inform future decisions aimed at promoting biodiversity in remnant bushland. Click here to see full article
At the 24th March meeting Sandra Guy, a wildlife rescue volunteer, spoke on flyingfoxes, and their key role in ensuring the ongoing health of ecosystems where animals are every bit as important as plants.
Sandra showed that most types of native forests across the continent depend on flying foxes to do the heavy lifting, pollinating hundreds of species of trees and ensuring genetic diversity and survival of many different types of forest communities. They are a ‘keystone species’, with an essential ecological role without which the ecosystem will collapse.
Many native trees have blossoms that are only receptive to pollination at night, and the only significant nocturnal pollinators are flying foxes. Without them, we will lose the structure that provides the essential microcosms supporting thousands of other flora and fauna species; yet few realise their key role. However, flying foxes are in decline and the main species on the eastern seaboard, the Grey Headed Flying Fox, may be extinct within 20-30 years.
It is time to examine Bats’ roles to see what can be done to save them. They seem so foreign to us, inhabiting the night skies; a realm so diametrically opposed to ours; myths and misunderstandings dominate our attitudes, and misinformation about their disease risk can cause great concern. Only recently have studies led to some understanding of their important role. They have existed for over 55 million years and are one of the most successful and abundant mammals.
There are two main types: the microbats (Microchiroptera) and the megabats (Megachiroptera). They are remarkably intelligent with highly sophisticated social structures. They are more intelligent than dogs and,in captivity, easily learn their own names and the routine of the house or aviary. They breed very slowly as mothers can only raise one pup a year. They form tight emotional bonds, teaching the pups grooming and social skills, until they become independent at about five months. If too long in human care, they become too dependent , and cannot be released into the wild.
They can travel up to 100kms a night foraging for food; returning each morning to an established campsite to rest, nap and socialise during the day. These campsites cause conflict with people, as they can be both odorous and noisy. Unfortunately, bats’ preferred residence is similar to ours, a sheltered gully near fresh water with tall trees and rich soil, protected from disturbing winds. As people clear bat habitat for their homes and farms, flying foxes are quickly losing both food sources and campsites. The problem of conflict with existing campsites is difficult. An experimental initiative to develop ‘replacement’ roost sites has recently commenced, aiming to entice the bats to leave problematic roosts in the middle of urban areas. Flying Foxes by Sandra Guy