In 2009, the Explaining Change Project created three sample areas close by the Hackett water tank. This was so we could assess the relative impacts of rabbit and kangaroo grazing. One plot excludes both kangaroos and rabbits, one plot excludes kangaroos but allows rabbits and the third plot is a control plot where both kangaroos and rabbits can graze. The first monitoring of these plots was done in November 2010 and follow up surveys have been done in 2011, 2012 and most recently 2013. The survey method was point-step monitoring. You can see the full report for years 2009-2012 here. In addition we have a photographic survey covering the same time period.
Because human memories of a changing scene – the when, what and how much – are inadequate, FoMM volunteers are using repeated photographs to record and so capture any changes. To be of real value, the photography must capture only the scene change, and not be affected by camera type and position, and lighting. Therefore, FoMM volunteers carefully repeat photographs from 22 separate positions (photopoints), at the same time of day (around midday) beginning when the fencing was completed (October, 2009), and now continuing every three months.
In addition to the photographic monitoring we assessed the ground-cover of the three plots using the ‘point-step’ method to monitor vegetation (Sharp S, Gould L: ACT Vegetation Monitoring Manual. A Step-by-step Guide to Monitoring Native Vegetation in the ACT. Greening Australia Capital Region 2010).
Rainfall in the months preceding the photographic records of October 2009 to July 2010 was around the corresponding long term average; rainfall in the three months preceding the photographic records end of October 2010 was significantly higher compared to the long term average (Graph showing the rainfall 2 (3) months before photographic records and the corresponding long term average).
We now have four full years of repeat photography available, October 2009 – October 2013. Sequences of still images were converted to video format for display on the YouTube website. During the three years of the project we have learned the strengths and weaknesses of our photography, and how best to present our results. That learning has been incorporated in our latest video.
Friends of Mt Majura Media Release Monday, 18 March, 2013
The grazing impact of Kangaroos: A three year experiment
The results of a three year experiment by a local ParkCare group demonstrate that grazing pressure by kangaroos has serious consequences for the integrity of endangered grassy woodlands.
Since late 2009, with financial help from the ACT Government and the North Canberra Community Council, the Friends of Mt Majura conducted a simple public awareness project by recording vegetation change, and demonstrating the cause.
“We set up our Explaining Change project to gain a better understanding of the relative influence of kangaroos, rabbits, and season on the herbaceous ground layer in the reserve”, Ms Waltraud Pix, coordinator of the Friends of Mount Majura explains. “We fenced small grassland areas to exclude kangaroos and rabbits, kangaroos only, or none of the two herbivores and recorded the changes of the ground layer with repeat photography at fixed times of the year.”
“Our project began during a prolonged drought in 2009. We were astonished to observe how the lawn-like grass layer recovered as a response to removing grazing pressure. With three years of repeat photographic records of the seasonal changes, and the separate impacts of kangaroos and rabbits, the evidence is now conclusive. Our records demonstrate that kangaroo grazing is the problem. Even under the favourable rainfall conditions grazing induced changes of the ground layer persist,” says Ms Pix.
“Protecting Yellow-box-Red Gum grassy woodland” is the stated purpose in creating, and thus managing Mt Majura Nature Reserve (MMNR). But one factor, which strongly influences the protection of this grassy woodland – grazing by kangaroos, is not managed. This is to be regretted because the kangaroo species, the Eastern Grey, is abundant and is under no threat of extinction. In contrast, there are many small populations of plant and small animal species in MMNR that are locally rare, and whose habitat is repeatedly grazed bare.
Does it matter? Based on years of experience working within the Reserve, The Friends are convinced that it does matter. In particular, it is obvious that grazing by kangaroos is both heavy and unsustainable, because there are too many of them in the small remaining grassy woodlands. The herbaceous layer, the grasses and forbs, is repeatedly reduced to a lawn or a cover of unpalatable weeds. Consequently, a large unmanaged kangaroo population defeats the purpose of protecting the grassy woodland.
Ms Pix has grave concerns that overgrazing undermines volunteer and government efforts to restore degraded grassy woodland. “Ultimately large scale restoration projects are not sustainable when overgrazing hampers the natural regeneration and the reproductive cycle of plants. Overgrazed landscapes would require continuous planting or direct seeding, and expensive measures to protect the plantings. What is the use of investing into the protecting, improving and restoring endangered grassy woodlands if we ignore a key factor that causes the degradation?”
A time-lapse video of the 3 years repeat photography and explanatory background information is available at http://majura.org/explaining-change/.
FoMM published the following photographic essays
Grazing impact on work to improve degraded woodland at the Majura ridge
Grazing impact on the ground cover and soil
End of Media Release