Operation Hollow Guardian
In the early hours of 06 and 18 September 2018, we embarked on a reconnaissance mission led by Dr. Phillip Gibbons. Armed with enthusiasm and a watchful eye, we infiltrated the urban suburbs of Canberra and its surrounding reserves and pasture land via land and vehicular insertion as part of an ongoing 7-year intelligence gathering operation regarding the biodiversity value of trees (different tree sizes in various landscape context).
We were tasked with the critical mission of surveilling the various trees for a duration of 20 minutes (Fischer and Lindenmayer, 2002), to determine identity and abundance of the bird species that came into physical contact with the tree, and their behavior and resource usage. The list of observed bird species is listed in Figure 1 below. Notably, we observed that bird species richness and abundance was higher in larger and more mature trees within urban and paddock landscapes than the trees within the reserves.
Figure 1. List of birds observed during the work experience.
Canberra’s current population is estimated to be around 411,401 persons and this figure is expected to reach half a million between 2032 – 2033 (ACT Government, 2014). To accommodate for such a parabolic surge in population, the rapid development of new suburbs and its associated infrastructures can be expected, and it appears likely that the “Bush”, due to the nature reserves surrounding Canberra and extensive urban tree cover (Banks and Brack, 2003), within the “Bush Capital”, will be affected.
Traditionally, such activities would encompass the large-scale clearing of existing habitats, including large established trees (Le Roux et al., 2014) and the dominant landscapes within Canberra currently, reserves, pastures, urban parkland and urban-built up areas (Le Roux et al., 2015), can be seen as a reflection of such development practices. However, these practices have led to the extensive (95%) decline in intact Box-Gum Grassy Woodland and its subsequent classification as a critically endangered ecological community (Department of the Environment and Energy, 2018).
Large and mature Eucalyptus trees are being understood as the Centres of Gravity within such a woodland habitat, whose removal can have a disproportionate adverse impact on the flora and fauna that depends on the ecological services it provides (Manning et al., 2006). Examples of such services include tree hollows, which requires approximately 120 – 220 years to form (Gibbons and Boak, 2002), and provides a home for hollow-nesting species as the superb parrot (Polytelis swainsonii) (Manning et al., 2013) and some of the bird identified in Figure 1 above.
Previously, private developers have turned to the planting of multiple smaller trees and artificial nest boxes to offset the loss of such large trees (Gibbons and Lindenmayer, 2007). However, the value of such an approach has yet to be proven (Lindenmayer et al., 2009) while clearance approval for such large isolated trees continues to be granted in non-reserve landscapes (Gibbons et al., 2009).
Figure 2. Employing Global Positioning System (GPS) to determine and confirm the location of trees of interest.
The intelligence operation conducted over these two days have established the presence and utilization of mature trees by several “High-Value Birds”, which contributes to the broader mission of mature tree conservation. The intelligence gathered will undergo further processing and analysis, and subsequently be produced into a brief (journal paper equivalent), which will be disseminated to policymakers within the government to enact legislative changes and protection. E.g. building code reform that requires developers to preserve and incorporate matures trees into their engineering and architectural plans rather clearing, and long-term forward planning by the government so as to initiate offsets earlier to mitigate concerns surrounding time lag.
Figure 3. In the field.
ACT GOVERNMENT. 2014. ACT Population Projects: 2013 to 2061 (Overview) [Online]. Australian Capital Territory, Canberra: ACT Chief Minister and Treasury Directorate. Available: Here [Accessed 23 September 2018].
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DEPARTMENT OF THE ENVIRONMENT AND ENERGY. 2018. White Box-Yellow Box-Blakely’s Red Gum Grassy Woodland and Derived Native Grassland in Community and Species Profile and Threats Database [Online]. Canberra: Department of the Environment. Available: Here [Accessed 24 September 2018].
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LINDENMAYER, D. B., WELSH, A., DONNELLY, C., CRANE, M., MICHAEL, D., MACGREGOR, C., MCBURNEY, L., MONTAGUE-DRAKE, R. & GIBBONS, P. 2009. Are nest boxes a viable alternative source of cavities for hollow-dependent animals? Long-term monitoring of nest box occupancy, pest use, and attrition. Biological Conservation, 142, 33-42.
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MANNING, A. D., FISCHER, J. & LINDENMAYER, D. B. 2006. Scattered trees are keystone structures–implications for conservation. Biological conservation, 132, 311-321.
Written by: U5992108