If you like it, then you should have kept the rings in it: Mature eucalypt tree loss will lead to decreased bird diversity in urban landscapes

By Caitlin Coward (u6051078). Word count: 500.

My work experience involved examining the value of mature eucalypt trees for bird diversity in the Canberra region as part of long-term research under the guidance of Phillip Gibbons.

Tall and proud: Importance of mature trees

Mature trees are crucial keystone structures for the survival of many species, namely birds, as they provide shelter in the form of hollows. Hollows form when a tree limb falls off and exposes the cavity where heartwood used to occur. This process only begins to occur between 120-220 years of age for a single eucalypt tree. Cutting down these mature trees for any reason destroys the centuries long progression of hollow development and is a large threat to biodiversity

Mature and unsure: Threats to mature trees

Balancing biodiversity preservation, like mature trees, with the increasing demand of urban expansion is a huge issue in conservation management. There are many anthropogenic reasons for removing mature trees: danger, inconveniently placed, roots can damage pipes, do not look nice, and to make room for urban expansion. The suburbs of Canberra are going to continue to expand with our increasing population (ref. Figure 1) and so the risk of mature tree loss will also increase as time goes by.

Figure 1. Residential housing at Bonner, ACT which was only a few hundred metres from remnant woodland (Coward 2019).

Leaf me to it: Independent surveying

On the 4th of September I went with Phil on a training session to learn the basic skills required to undertake an independent survey. In the early hours of 20th of September I went to three sites around northern Canberra to undertake my independent survey (ref. Figure 2). I surveyed one tree in each of the following land use areas: leasehold property tree Gp-kh2 (E. blakelyi), reserve tree Gp-ks1 (E. melliodora), and urban environment tree Gu-ks2 (E. blakelyi) (ref. Figure 3). The survey duration was 20 minutes per tree, where I collected data like bird diversity, arrival and departure location, behaviours, and duration of stay (ref. Table 1). I was also given a sheet with some common Canberran birds which helped identify species (ref. Figure 4).

Figure 2. Location of all eucalypt trees in the Canberran study (left) and zoomed in location of the three surveyed eucalypt trees (right) (Google 2019).
Figure 3. Three mature eucalypt trees around Canberra part of ongoing research. Leasehold property tree Gp-kh2 (left), reserve tree Gp-ks1 (middle), and urban environment tree Gu-ks2 (right) (Coward 2019).
Table 1. Example of data collection sheet, where one was scribed for each tree.
Figure 4. Some common bird species found during the surveys. Eastern rosella (top left), magpie (top right), European starling (bottom left), and sulphur-crested cockatoo (bottom right) (Coward 2019).

Turning a new leaf: Conserving mature trees

Increasing tree size positively correlates with increasing bird diversity. We must sustainably manage trees of all ages to continue the cycle where young trees replace the old and improve our management practices. Additionally, we should not cut down old or dead trees as they can still provide the service of hollows (ref. Figure 5). There is little risk of falling branches striking someone, though removing problem branches is a simple way to eliminate this issue. The preservation of these mature trees in urban landscapes is paramount for protecting biodiversity.

Figure 5. Sulphur-crested cockatoos utilising the hollows of a dead eucalypt tree (Coward 2019).

Growing up: Personal conclusion

I did not realise the importance of eucalypt hollows until doing this work experience. This has really opened my eyes to ecological processes I glance over every day. I now look at eucalypt trees with a new-found appreciation and am always on the lookout for birds using hollows.

Acknowledgements

Thank you to Phil for taking the time out of his busy schedule to facilitate this work experience.

References

All images: Coward, Caitlin. 2019. JPG.

Ellison, M.J. 2005. Quantified tree risk assessment used in the management of amenity trees, Journal of Arboriculture, 31(2): 57-65.

Gibbons, P. & Lindenmayer, D.B. 2002. Tree hollows and wildlife conservation in Australia. CSIRO publishing, Victoria.

Gibbons, P. 2018, ‘Smart city planning can preserve old trees and the wildlife that needs them’, The Conversation, 2 July 2018, viewed 20 October 2019, https://theconversation.com/smart-city-planning-can-preserve-old-trees-and-the-wildlife-that-needs-them-98632

Google, 2019. ‘ACT tree study’, Google Maps, viewed 25 October 2019, https://www.google.com/maps/d/u/0/viewer?mid=1wO7wqRgh2eAvSKuEYi7OWpP80_M&ll=-35.16921386746231%2C149.10879826270366&z=13

Le Roux, D.S., Ikin, K., Lindenmayer, D.B., Manning, A.D., Gibbons, P. 2014. The Future of Large Old Trees in Urban Landscapes, PLoS One, 9(6): e99403.

Le Roux, D.S., Ikin, K., Lindenmayer, D.B., Manning, A.D., Gibbons, P. 2015. Single large or several small? Applying biogeographic principles to tree-level conservation and biodiversity offsets, Biological Conservation, 191(1): 558-566.

Manning, A.D., Fischer, J., Lindenmayer, D.B. 2006. Scattered trees are keystone structures – Implications for conservation, Biological Conservation, 132(1): 311-321.

Stagoll, K., Lindenmayer, D.B., Knight, E., Fischer, J., Manning, A.D. 2012. Large trees are keystone structures in urban parks, Conservation Letters, 5(1): 115-122.

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A straw shows which way the wind blows: Threatened biodiversity in Australian Capital Territory

Jiacheng He (U5931175)

The Australian Capital Territory (ACT), where contains the Australian capital city of Canberra and other surrounding townships, is developed throughout the 20th century. During the development of the ACT region, original landscapes were largely modified (Finlayson, 2012). Artificial disturbances strongly influenced regional biodiversity, various species and ecological communities were listed as endangered/critically endangered in recent decades, such as the Swift Parrot (Lathamus discolor) and the Yellow Box/Red Gum Grassy Woodland. My volunteer experience includes a bird survey with Assoc. Prof. Philip Gibbons, and a natural reserve maintenance with the Friends of Mount Majura (FoMM). Two working experiences provided me some similar perspectives about the status of biodiversity (and the conservation) in the ACT area.

The Bird Survey

Picture 1. Isolated mature tree. Photoed by Jiacheng He

This survey began in a sunny morning, we divided into pair-work groups then evaluated the ecological value of mature trees on different study sites (on nature reserves, public greenspaces and leasehold properties). The adopted method was observing and recording the frequency/abundance of bird presence/behaviour on certain mature trees. Expected and actually observed bird species include Crimson Rosella (Platycercus elegans), sulphur-crested cockatoo (Cacatua galerita), pied currawong (Strepera graculina) and noisy miner (Manorina melanocephala).

Picture 2. Sulphur-crested cockatoo in the hollow. Photoed by Jiacheng He

As a continuous research plan, bird surveys are designed to demonstrate that compensatory small trees cannot adequately be the offset of large old trees. According to the prior publications (Le Roux et al., 2014; Le Roux et al., 2015), mature trees are able to provide more favourable habitats for various bird species with breeding hollows. Also, there is no doubt that planting new and smaller trees are important in the urban landscapes. For the reason that increasing paddock trees indicate better habitat connectivity in the future.

During the survey, Phil introduced a lot about the conservation status of these isolated mature trees. In the ACT area, population increase stimulated the urban expansion. And developmental plans prefer to fully clear most of the mature trees rather than keep necessary numbers of them. And it’s a pity to hear that several study sites will be cleared for residential constructions.

Picture 3. The area to be cleared for constuctions. Photoed by Jiacheng He

Jobs at The Fair Project Site

Picture 4. Entrance of The Fair Project Site. Photoed by Jiacheng He

I gained a work opportunity at the Fair Project Site, where is a small part of the Mt. Majura nature reserve. Waltraud, the project manager of the FoMM, introduced me about the site and some background knowledges. Other volunteers and I started from the weed control, and we focused on the Paterson’s Curse (Echinum plantagineum).

Picture 5. Paterson’s Curse. Avaliable from the Agriculture Victoria

This herb species is the most numerous weed species on the Fair site, and it is an invasive species that can rapidly seed after the blossom. We excluded every Paterson’s Curse we found, and the plants with flowers were gathered and taken out of the site.

Picture 6. Mulching. Photoed by Jiacheng He

Then we mulched for regenerated plant species, mulching can suppress growth of weeds, maintain humidity, prevent soil erosion and add nutrients to the soil. During the job, we talked about the environmental degradations on the site. The major degradations are considered to be: soil compaction due to the urbanization; weed invasion due to inappropriate past land management; loss of topsoil and understorey diversity due to overgrazing. It was emphasized that all the conserving offsets of this site own no governmental funds. And the FoMM can only conserve and re-plant endangered species but cannot deal with the kangaroo overgrazing.

Picture 7. Protected and regenerated species. Photoed by Jiacheng He

Work experiences with Phil and Waltraud let me realize that the biodiversity in ACT is still facing various threats, although many conservation plans have been applied. The government/decision makers should concern more about the degrading biodiversity and try to find feasible solutions (i.e. limit the urbanization; support significant conservation; control the kangaroo overpopulation).

Picture 8. Offsets on The Fair Project Site

References

Finlayson, D. (2012). Canberra landscapes shaped by geology: the centenary of Pittman’s 1910 geological map that helped shape the design for Australia’s capital city. Canberra Historical Journal 69: 1-4.

Le Roux, D.S., Ikin, K., Lindenmayer, D.B., Manning, A.D., Gibbons, P. (2014). The Future of Large Old Trees in Urban Landscapes. PLOS One 9(6): e99403.

Le Roux, D.S., Ikin, K., Lindenmayer, D.B., Manning, A.D., Gibbons, P. (2015). Single large or several small? Applying biogeographic principles to tree-level conservation and biodiversity offsets. Biological Conservation 191: 558-566.

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Volunteering with researchers from around the world to conserve biodiversity

In the first week of semester I had the opportunity to accompany several researchers on a field trip to Narrabri, in north western New South Wales. This field trip was one component of a project involving the collaboration of researchers from Harvard University, the University of Canberra, and the Australian National Wildlife Collection (ANWC), CSIRO.

A recent study (Burley, 2017) has identified a chromosomal rearrangement unique to the honeyeater (Meliphagidae) family. As such, the overall aim of the current project was to further understand the evolution and consequences for gene expression of this unique chromosomal system which has evolved in Australian songbirds.

To address this, field work was conducted to obtain relevant tissues suitable for establishment of cell lines and chromosomal and genetic analysis from various honeyeater (Meliphagidae) and thornbill (Acanthizidae) species. Laboratory work was then to be conducted using in situ hybridisation to determine the physical location of gene sequences on specific chromosomes.

To document the species harbouring chromosomal arrangements, voucher specimens were prepared for deposition in the ANWC (CSIRO) and the Museum of Comparative Zoology (Harvard, USA). These specimens provide reference anchor points for all future analyses of the data derived from the specimens; an extremely important point, in the case that something unexpected is found.

Significance of this study

Research of this nature, such as studying how the genomes of non-human animals evolved is vital in order to put in context how humans and other vertebrates evolved, and how bird evolution is unique relative to other vertebrates. As these data will improve the understanding scientists have of the basic structure of genomes of Australian songbirds, they may prove vital in the genetic management of endangered honeyeaters and songbirds.

Simply knowing where genes are located in the genome helps scientists understand how such species are manipulating genetic diversity. Understanding the taxonomic scope and prevalence of chromosomal rearrangements is one way to help researchers interpret the results of genetic surveys of diverse species, which in turn will be crucial in future species conservation efforts.

An example demonstrating the importance of such data in the context of conservation, is the recent research and subsequent publications by Dolman and Joseph which led to the split of one avian species, into two distinct species. The Chestnut Quail-thrush (Cinclosoma castanotum) was split into two species, C. castanotum and the Copper-backed Quail-thrush (Cinclosoma clarum). As such, any conservation and management strategies can be implemented as appropriate with respect to the relevant Cinclosoma species.

A tour of the Australian National Wildlife Collection (ANWC)

Upon arrival back in Canberra, I was invited into the ANWC where the collection manager guided me around the collection. I was able to observe just a small fraction of the many thousands of specimens the ANWC holds, and I gained a huge appreciation of the scientific value each specimen and its associated data.

It was here that I was informed just how large this collection is, and of its great importance, as it is a vital archive for the research and conservation of Australia’s terrestrial vertebrate biodiversity.

This collection holds almost 200,000 irreplaceable specimens which represent 99% of Australian birds, 75% of Australian mammals, 60% of Australian reptiles, 70% of Australian amphibians. The ANWC is also the leading repository for heritage egg collections, holding eggs from over 1000 species.

Importance of biological collections for conservation

Natural research collections dating back to the late 1700’s, underpin a significant amount of research conducted by Australian and international scientists on taxonomy, population genetics, biogeography and ecology.

CSIRO has several federally gazetted natural history collections, which are a fundamental scientific resource and are pivotal for biodiversity conservation and management. These include the ANWC, the Australian National Insect Collection (ANIC), the Australian National Herbarium (ANH), and the Australian National Fish Collection (ANFC).

Today, the ANWC is revealing how birds are responding to climate change, and importantly holds irreplaceable records for historical species distributions for restoration projects.

ANIC contributes to protecting Australia’s biodiversity, enabling the identification of insects at Australia borders, while also revealing how insecticide resistance develops.

ANH supports threatened species recovery and weed seed identification at the Australian borders.

Without these natural research collections, much of what we know about Australia’s biodiversity including evolution, and population genetics would not have been possible and as such the conservation status of many species may not have been established; only time will tell what is yet to be discovered.

Reference
Burley, J. (2017). ‘Reticulate Evolution of an Australo-Papuan Songbird Inferred Using Whole-genome Sequencing.’ (M.Sc. thesis, Uppsala University: Uppsala.)

Author: U6079558

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Tree watching (bird surveys)

Biodiversity and development are often seen at mutually exclusive terms, with one prevailing at the expense of the other. Can biodiversity be maintained within the bounds of urban development by prioritising conservation of important mature trees? How do we know if a tree is mature and important? Well, we watch them of course.

The abundance and frequency of bird visits to certain trees is an indicator of ecological importance. Mature trees with hollows provide habitats for various bird species that cannot be supplied by young trees , hence older, more mature trees are believed to be more ecologically important that younger trees. We set out to further this quest for knowledge.

My work experience was punctuated by relaxing moments of reclining in the sun, panicked scribbling of bird related information and collective swearing when birds skipped our survey trees (quickly dubbed a ‘fly by’). Armed with a clipboard, limited knowledge on common bird species and a complicated record keeping system we began surveying the birds (tree watching).

A mature Eucaluptus with deep hollows providing habitat and nesting for Cockatoos.
Source: Lily O’Brien

In a project run by Phil Gibbons, multiple (primarily Eucaluptus ) trees were selected at random to be monitored for their abundance of bird species, with the aim of determining the features of trees that birds prefer, with the intention of advising developers on the value of preserving mature trees. We were entrusted with the job of recording bird species, direction of flight and activity whilst on the target tree. These target trees ranged from paddock trees in farmland, trees fringing urban development to those on reserves.  

Constant Vigilance was necessary- spring in full force.
Source: Lily O’Brien

Mature trees with large, overhanging dead branches are dangerous to developers; branches fall on people, they’re not aesthetically pleasing and they get in the way of good old-fashioned urban sprawl. Never fear, biodiversity offsets are a foolproof mechanism to account for the loss of biodiversity (sarcasm).

Mature trees often do not develop large hollows before 220 years , meaning the effectiveness of offsets is restricted to future benefits, not accounting for biodiversity losses that impact native species now. This also means that trees are being removed faster than they can be regenerated. Offset proposals often don’t account for this time differential.

In one mature hollow bearing tree, we saw Cockatoos nesting in the hollow, Eastern Rosellas and Magpies over a 20 minute period. In addition to habitat provisioning, mature trees provide steppingstones for migration across a landscape. We experienced this watching Cockatoos fly across grassland in Goorooyarroo nature reserve, stopping at large Eucalupts before continuing their journey.

Never again will I look at mature trees the same way.

u6046813

References:

Fischer, J. and Lindenmayer, D. B. (2002) ‘The conservation value of paddock trees for birds in a variegated landscape in southern New South Wales. 2. Paddock trees as stepping stones’, Biodiversity & Conservation, 11(5), pp. 833-849.

Gibbons, P., Macintosh, A., Constable, A. and Hayashi, K. (2017) ‘Outcomes from 10 years of biodiversity offsetting’, Global Change Biology, 24.

Hannan, L., Roux, D., Milner, R. and Gibbons, P. (2019) ‘Erecting dead trees and utility poles to offset the loss of mature trees’, Biological Conservation, 236.

Le Roux, D., Ikin, K., Lindenmayer, D., Manning, A. and Gibbons, P. (2015) ‘Single large or several small? Applying biogeographic principles to tree-level conservation and biodiversity offsets’, Biological Conservation, 191, pp. 558–566.

Office of Environment and Heritage (2017) Loss of Hollow Bearing Trees. Threatened Species Office of Environment and Heritage Available at: https://www.environment.nsw.gov.au/threatenedspeciesapp/profile.aspx?id=20079 2019).

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A Hollow Future: Impacts of Urban Development on Canberra’s Bird Populations

By u6043246, Jarrod Ward

What’s the Problem?

Canberra’s ever expanding population, currently sitting around 420,000 and projected to expand to 703,000 by 2058, means we are constantly building new suburbs such as the Molonglo Valley development. This has the consequence of making old, hollow bearing trees an increasing rarity as they are often immediately removed for a number of reasons. This poses a serious problem for many of the local native bird species which rely on these structures for breeding.

A male Superb Parrot photographed by Elliot Leach. These birds are suffering as a result of common urban development policies.

The Project

Philip Gibbons, an Associate Professor at ANU, has been surveying bird interaction with a range of trees that vary in age, species, structure and location. In doing this, it can be established which trees are most important for bird interaction so that future development policy can be influenced to preserve trees with the highest biodiversity impact. I was lucky enough to join Phil along with some other volunteers for two of these bird surveys during September, with the breeding season occurring during this month and October, bird interaction is highest at these times. One of these trees is pictured below.

A large tree in a field

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Field Experience

Surveys took place early in the morning, checking multiple trees on each trip. For 20 minutes, all bird interaction with the surveyed tree was recorded. The direction they flew in from, the direction they flow out to, what they did in the tree and how long they spent there was some of the major factors that were noted for each individual bird. The most common birds that we observed during the field work included;

The Crimson Rosella (top left) photographed by Julie Clark. Sulfur Crested Cockatoo (top right) photographed by Sandra Gallienne. Pied Currawong (bottom left) photographed by Corey Callaghan. Noisy Miner (bottom right) photographed by Andrew Allan. All photographers can be found on ebird.org.

A bird species that we unfortunately didn’t get to see, likely due to the decline in breeding hollows across Canberra, is the Suberb Parrot. This parrot is currently considered vulnerable under commonwealth status with less than 5000 breeding pairs estimated to remain in the wild.

Whats the Goal?

Using quantitative surveys, Professor Gibbons aims to demonstrate the importance of older, senescent trees over younger ones. These trees can take up to 100 years to form the necessary hollows for the local native birds. If policy decision in the ACT can be changed to specifically save the older trees over younger ones in future developments than the possible breeding grounds for native wildlife will be increased, as well as the overall biodiversity of the area as the tree is used as an ecological stepping-stone.

A Sulfur Crested Cockatoo peeking from its hollow while we survey a tree nearby.
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Planting for the Future: Regenerative and Restorative Agriculture

AUGUSTA MUTTON U6077630

Perrumba, an Aboriginal word for wattle blossom, is a permaculture-based farm in Bungonia, New South Wales. This land has been under the care of Debbie Hunt and Kieron Malone for over 7 years now, where they are almost fully self-sufficient, run environmental workshops, and share their expertise in permaculture and sustainability with the community. Bungonia is a spectacular part of our country, and Perrumba endeavours to preserve and protect this landscape and all of the native plants and animals that share it.

PROMOTING ECOSYSTEM FUNCTION AND RESTORATION

Debbie graciously invited me to Perrumba to experience working on regenerative and restorative agriculture. We spent the morning planting Eucalyptus trees and species of Casuarina, to support the local population of vulnerable Glossy Black Cockatoos (Calyptorhynchus lathami), which use Eucalypts and Casuarinas as food and habitat sources.

Source: Australian Museum.
Two Glossy Black Cockatoos.

We discussed the importance of retaining the current mature trees on the farm for their hollows and complex habitats, and the importance of planting new trees to promote the creation of habitat and food resources well into the future. The tree planting was done in a section of a previously cleared and grazed paddock, and was chosen as it would create not only habitat and food sources for the cockatoo in the future, but also exist as a corridor between surrounding woodland habitat, increasing the connectivity between populations of many species and ultimately reducing fragmentation.

Source: Augusta Mutton.
Eucalyptus and Casuarina planting at Perrumba Farm.

FRAGMENTATION AS A THREAT TO BIODIVERSITY

Throughout biodiversity research, fragmentation has been shown to be a major threat to the survival and gene flow of populations. Creating corridors for immigration and emigration, gene flow, and access to resources is essential to support healthy populations by reducing the risk of inbreeding and stochastic events (environmental and demographic). It is essential for private landowners to promote this sort of biodiversity conservation to ensure there is representative management of different ecosystems throughout the country, as parks and reserves are often insufficient. Creating flexible land management and monitoring methods is essential to prepare for the challenges of the future, including severe, unpredictable weather patterns due to climate change, and will ensure long-term conservation of the region and promote active learning through adaptive management.

Another way we contributed to biodiversity conservation throughout the day was by attracting pollinators using seed balls, which included the seeds of native and non-native flowers. This promotes natural systems to function in favour of food production, by encouraging a diversity of pollinators. This system also stimulates tree regeneration throughout the farm, as some seed balls included Eucalyptus seeds and were seasoned with paprika to keep the ants away!

Source: Augusta Mutton
Seed balls made of clay air drying, in preparation to be cast throughout regeneration areas at Perrumba.

LOCAL LEVEL CONSERVATION

The lifestyle and activities carried out at Perrumba support conservation on many levels, particularly by promoting ecosystem function, protecting and enhancing the environment, and planning for the future. Their actions are providing more complex, resilient, connected, and sustainable ecosystems for populations and habitats to thrive. The importance of every contribution to the ecosystem is recognised at Perrumba; a holistic view of symbiotic human and environment interactions are represented through their values. From retaining fallen and mature trees for their habitat complexity, promoting pollinators like bees and birds, using chickens to turn over the soil, home-composting and recycling into the soil, acknowledging the different levels of ecosystem services, and most importantly, creating awareness in the community for sustainability and conservation, Perrumba is promoting local biodiversity.  

Source: Augusta Mutton
A sign at the entrance to Perrumba Farm, encompassing their values of supporting local wildlife.

This protected landscape is home to an impressive list of bird, reptile and mammal species, further suggesting how important private conservation, citizen science and community inclusion is to restoring and regenerating ecosystems.
The purpose of Debbie & Kieron’s work at Perrumba is predominantly for food security, self-sufficiency, and supporting local biodiversity, but is also focused on using the values of permaculture and regenerative agriculture to preserve and restore this beautiful part of Australia, leaving the land more functional and resilient than how they found it.

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Removing Horehound weed with Friends of Mount Majura (FoMM)

As a part of my volunteer work experience I joined the Friends of Mount Majura (FoMM) volunteer team to assist with some essential conservation activities, one of which involving the removal of horehound (Marrubium vulgare), an invasive weed species that infests a number of sites on the ridge between the Mt Majura Nature Reserve (MMNR) and the Mt Ainslie Nature Reserve (MANR).

The Horehound Blitz weeding upon the Mt Majura Ridge was paired with marvellous views of Majura valley and north Canberra.

Horehound is widespread across Australia after being introduced from Europe, the Middle East and northern Africa during the 19th century as a result of livestock grazing. It is therefore abundant in nutrient rich soils and areas of high disturbance due to overgrazing. After speaking with one of the FoMM volunteers, Waltraud Pix, it became evident that grazing, particularly of sheep, is the primary culprit for the presence of horehound on the ridge. The sheep migrate to the ridge where they prefer the warmer temperatures and sunlight during winter and cool breezes during summer, consequently dispersing their droppings in a concentrated area to produce patches of weed prone soils containing high levels of nutrients. After being introduced to the causes and impacts of horehound, we set off with our spades and pickaxes to remove as much horehound as possible!

Horehound weed (Marrubium vulgare) removal in action.
Post-removal of horehound weed (Marrubium vulgare) after using my trusty pickaxe.

As illustrated in week 9, weed infestations have the capacity to destroy native habitats by completely transforming natural ecological systems. Invasive weeds such as horehound are thus increasingly problematic to the Australian landscape by threatening native plants and wildlife. However, there are some feasible impact prevention management activities occurring that aim at supressing horehound infestation for good.

In addition to ongoing weed removal by FoMM and Park Care volunteers, I was introduced to an alternative weed management treatment currently in place at the Mt Majura ridge. This involves placing a thin layer (<100mm) of organic mulch over an infested soil patch to assist in the regeneration of native grasses, herbs and shrubs. Since invasive plants prefer nutrient-abundant soils and natives do not, the theory of one of the FoMM volunteers, Waltraud Pix, is that the mulch acts as a protective layer for the soil beneath by retaining moisture and basic nutrients that native plants prefer. Soil microbial processes of decomposition and nutrient cycling are then expected to take up any abundant soil nutrients, leading to a patch of soil that is less prone to weed invasion while also reducing the use of harmful pesticides. The mulching treatment had been implemented on the patch that we were weeding on the Mt Majura ridge around 6 months ago, and so the FoMM volunteers are closely monitoring the site to assess its short and long-term effectiveness.

Small patch of organic mulch treatment covering the horehound infested area upon the Mt Majura Ridge, along with one of our many piles of removed horehound weed.

Despite countless efforts of weed management and native regeneration by the FoMM Park Care volunteer team, they have encountered many limitations due to limited government funding and stakeholder engagement. I was informed by FoMM volunteers that they are very reliant upon the involvement of the community, however their conservations efforts should be further supported by the funding and awareness of the state and federal government. Nonetheless, the FoMM Park Care group are determined to encourage more communities and stakeholders to be actively involved in their conservation work while improving the quality of native landscapes and assisting in the conservation of wildlife across the Canberra region for years to come.

References

Australian Government, 2019, Impact of Weeds, Available from: Weeds in Australia – About Weeds, https://www.environment.gov.au/biodiversity/invasive/weeds/weeds/why/impact.html (Accessed 20 October 2019).

Callaway, R.M., Thelen, G.C., Rodriguez, A. and Holben, W.E., 2004. Soil biota and exotic plant invasion. Nature, 427(6976): p.731.

Camenzind, T., Hättenschwiler, S., Treseder, K.K., Lehmann, A. and Rillig, M.C., 2018. Nutrient limitation of soil microbial processes in tropical forests. Ecological Monographs, 88(1): pp.4-21.

Coutts-Smith, A. and Downey, P.O., 2006. Impact of weeds on threatened biodiversity in New South Wales. Adelaide: CRC for Australian Weed Management.

Downey, P.O., 2006. The weed impact to native species (WINS) assessment tool–results from a trial for bridal creeper (Asparagus asparagoides (L.) Druce) and ground asparagus (Asparagus aethiopicus L.) in southern New South Wales. Plant Protection Quarterly, 21(3): p.109.

Grice, A.C. 2004. Perennial grass weeds in Australia: impacts, conflicts of interest and management issues, Plant Protection Quarterly, 19(2): 42-47.

Humphries, S.E., 1993. Environmental impact of weeds. In Proceedings II of the 10th Australian Weeds Conference and 14th Asian Pacific Weed Science Society Conference, Brisbane, Australia, 6-10 September, pp. 1-11.

Pix, W. 2019, Horehound Blitz, Available from: Friends of Mount Majura, http://majura.org/horehound-blitz-20-10-2019/ (Accessed 15 September 2019).

Sinden, J., Jones, R., Hester, S., Odom, D., Kalisch, C., James, R., Cacho, O. and Griffith, G., 2004. The economic impact of weeds in Australia. Technical Series, 8.

Thackway, R. and Freudenberger, D., 2016. Accounting for the drivers that degrade and restore landscape functions in Australia. Land, 5(4): p.40.

Weiss, J. and Sagliocco, J.L. 2000. Horehound (Marrubium vulgare): a comparison between European and Australian populations, Plant Protection Quarterly, 15(1): 18-20.

Wilson, P.D., Downey, P.O., Leishman, M., Gallager, R., Hughes, L. and O’Donnell, J. 2009. Weeds in a Warmer World: Predicting the Impact of Climate Change on Australia’s Alien Plant Species Using MaxEnt, Plant Protection Quarterly, 24(3): 84.

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Horehound Hunters: Weeding out invasive species at Mt Majura

By u6051787

A Brief History

Mt Majura is a towering feature of Canberra, with its scenic hikes, stunning views, and abundant biodiversity. It’s hard to miss as it stands 890 metres above sea level, making it Canberra’s highest peak. However, the history of the mountain and its surrounding reserve has not always been so picturesque. In the 1830’s the naturally treeless grassy plains attracted sheep farmers to the region. Livestock grazing became the norm and, over 150 years, it drastically altered the environment.

FoMM weeding at Mt Majura ridge. Photo taken by author.

The Weed Invasion

I volunteered with the Friends of Mt Majura (FoMM) group and spent the day destroying Marrubium vulgare L. (horehound) regrowth. Horehound is a woody, perennial weed that has a natural distribution in Europe, the Middle East, and the Mediterranean region. Its burr seed has allowed it to disperse to and over the Mt Majura reserve by clinging to the fur of stock and other animals. Once established the plant is highly unpalatable as it contains a bitter alkaloid. The surrounding vegetation becomes targeted by grazing which leads to the clearing of competing species. This allows horehound to persist and increase in the environment.

Horehound weed. Photo taken by author.

Horehound can only overtake areas of previously disturbed native vegetation and this is what had occurred at a former sheep camp on the reserve. We spent the day clearing the area which, until last year, had been completely overrun with horehound. This land would have been targeted by livestock due to its desirable climate. It sits at a higher altitude and is positioned between Mt Majura and Mt Ainslie making it warmer in winter and breezier in summer. The stock would have congregated here, leading to overgrazing and an increase in soil nutrients. Most native vegetation is adapted to nutrient depleted soils and cannot survive where nutrients are too high. Horehound, however, thrives off it. For years it grew, undisturbed, over the whole reserve. It was destroying any chance of native plant regeneration, until 13 years ago when the community decided to take the land back.

The Retaliation

Thousands of hours of community time has been spent trying to get the land back to something similar to its original box-gum grassy-woodland state. The aim for FoMM  is to remove all traces of horehound from the 5 hectare area of the former sheep camp. I contributed to this large scale project armed with a pickaxe and a trowel. Whilst some weeds can be killed by removing the exposed stem, this is not the case for horehound. It was important to remove the majority of the root to prevent the weed from re-establishing. This was difficult as it was rooted in rock crevasses and hard, compact soil.

Left image: Getting ready to weed on the old sheep camp at Mt Majura.
Right image: Using a trowel to remove horehound.

Luckily these weeds were still young since 6 months ago the FoMM group had cleared this area and laid down woody mulch. The mulch retains soil moisture by creating a barrier that decreases evaporation. It also provides microbes and fungi that decompose the organic matter, which help to take up the nutrients in the soil. The reduction in nutrients creates a better environment for native vegetation and decreases the chance of invasive species taking over. This can already be seen in the reserve as native plants have been popping up more and more frequently.

What’s next?

Whilst the community has worked extremely hard to fend off the onslaught of invasive weeds, more government support is needed. Horehound and many other woody weeds are not recognised as a threat for native woodland. It is important that awareness surrounding the destructive impact of these weeds on biodiversity is improved. Funding should also be increased to support the amazing community work.

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What can we bring to birds while urban developing?

Introduction and Background

written by Jiacheng Yong (u6248417)

Due to various reasons, such as immigration, comfortable living environment, the population in Canberra has experienced a rapid increase. This trend drives local government to develop brand new residential areas vigorously to satisfied increasing living demands. However, urban developing (building new residential areas) inevitably leads to impacts on wildlife living in original areas, especially birds. Similar situation happens everywhere in the world. We can kid ourselves that this is necessary sacrifices during economic or social development at the beginning, but continuous urban area expansion reminds us that we must try to protect these bird species and find a balance point between biodiversity and urban development. Therefore, I attended the research organized by Dr. Gibbons targeting on identifying the value of mature trees for birds. 

Photograph of common bird species in Canberra (Google Photos, 2019)

Biodiversity threats of birds in urban area

Dr. Gibbons shared a lot of views to biodiversity conservation in urban areas in Week 7. During the process of urbanization, original landscape and biodiversity structure are suffering from modification. Obviously, there are fewer trees, dead trees, hollow-bearing trees, native plants in urban areas in Canberra than those in nature reserves. Unfortunately, the terrible impacts caused by urbanization bring birds in Canberra a lot of challenges. Around 29% of the birds prefer using mature native trees (>80cm diameter) in the ACT.

A comparison of the amount of habitat in reserve, pasture and urban open space in Canberra (Le Roux et al., 2014)

Working process and results

My job was only observing the target tree for 20 minutes and recorded if there were any birds and further activities. I assisted Philip Gibbons, my lecturer, on 19th September and Julia Paschal on 23rd September. We were divided into several groups to observe target trees through professional telescopes, where the trees were marked in advance. Most of the trees were isolated because we also need to identify whether isolated trees can attract birds more. The results reflected that bird species like using trees > 80cm diameter, and isolated trees in urban land support more bird species  I also put forward a question, using telescope still means group members have a very close distance to target trees. Will it scare birds and bring bias to the survey? It might be better if we can use some hidden cameras instead of observing trees artificially.  

One of the isolated target trees (photo supplied by author)
a cockatoo in hollow of target tree (photo supplied by author)
Results of survey on 19th September (photo supplied by author)
Results of survey on 23rd September (photo supplied by author)

What should it be in future?

As Conservation Biology indicated, there is a positive correlation between people’s satisfaction with neighbourhoods and richness of birds. We really need to understand the importance of biodiversity to our daily life. We really need to ensure that urbanization is running in a sustainable way and maintaining enough landscapes (especially trees with 80cm diameter or larger) for birds in urban area.

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Volunteer tree planting in Googong

Planting trees with the local community

In the first weekend of October, I was privileged to participate in a volunteering event organised by the Conservation Volunteers and Forestry Corporation in the newly developed suburb of Googong. The primary goal of the event was to plant trees and shrubs to restore the native vegetation around the surrounding area of the suburb. Besides, the event also aimed to raise the local resident’s awareness of environmental stewardship, to cultivate the sense of responsible use of the natural environment and active preservation of biodiversity across the neighbourhoods.

Even though I selected forest management and my minor, I haven’t got a chance to actually plan a tree or other vegetation by myself. This volunteering event provided me with some valuable hand-on experience on tree planting and habitat revegetation.  For tree planting, I learnt some practical tips such rocks and dead logs could be used as an effective shelter for small trees to against the wind, the tree protectors with different colour could be used to identify different species and provide convenience for the follow-up management etc. For habitat revegetation, I leant that the planted species should be diversified. For grasses, we planted short wallaby-grass (Rytidosperma carphoides) and river tussock (Poa labillardieri). For shrubs, we planted chamomile sunray (Rhodanthe anthemoides) – a daisy with small white flowers. For trees, we planted yellow box (Eucalyptus melliodora ) and golden wattle (Acacia pycnantha). The ration of planting grass, shrubs and trees is about 10:3:1. This ratio enables a lower mortality rate and even nutrition absorption among different species to form a rich structural complexity in the future.


Volunteers planting vegetations in the newly developed Googong suburb

Significance of afforestation to a newly developed suburb

The revegetation event itself is highly relevant to the two themes which are emphasised in the course of biodiversity conservation: habitat conservation in the urban context and stakeholder engagement. With the result of severe habitat fragmentation and deterioration, the continuous urban development could cause severe threat on some of the listed endangered species. Hence, revegetation in the urban area could help to reconnect the fragmented habitat for native birds and reptiles. Besides the ecological preservative, it could also increase the property value based on the numbers of large trees and rich biodiversity level of the adjacent area. Additionally, there is research indicates that more green space around the residential areas could also increase the mental and physical wellbeing of residents.

Volunteer, local resdient and Forestry Corporation Staff planting trees together.

Alter the traditional bias of forestry company

During the lunch break, I happened to have a conversation with Sean one of the co-organisers of the revegetation event and the manager assistance manager of the Forestry Corporation. Sean shared with me a different perspective from the forestry company. He told me that for him the aim of supporting this event is to change people’s bias on forest industries. For a long period of time, people shared a bias that the forestry is a selfish business making benefit from excessive logging and land clearing. Supporting such local revegetation program showcased that the corporate social responsibility and sustainable development are fully recognised the Forestry Corporation and would hopefully change people’s mindset on forestry.

By working with other industrious volunteers as well as the enthusiastic Googong residents, about 800 trees and vegetation were planted in only two days. Even though the volunteering experience is exhausting, the sense of and excitement achievement of changing the infertile grassland into a greenery vegetated landscape is more than words can express.

Yufeng Song – U5988528

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