Category Archives: Current research

Invertebrate use of rooftops in Melbourne

Green roofs are a peculiar kind of designed habitat. In already highly urbanised areas, where there is large pressure on efficient land use, green roof retrofits are a key strategy to bring back nature without losing building capital.

While green roofs are known to have many economic and social benefits, such as stormwater retention and thermal buffering, their usefulness as wildlife habitat remains an open question. Multiple studies record insects, birds, spiders and other animals existing on green roofs, but there is little known as to how (and if) they are subsisting, or indeed what they are doing up there.

Native Halictid bee visiting a native Scaveola flower on the Parliament green roof. Photo Credit: Jess Baumann.

This is the focus of a new study by ICON Science researchers Georgia Garrard and Katherine Berthon, and research assistant Jess Baumann, who are setting out to document how animals (particularly birds and insects) are using green roofs in the City of Melbourne by monitoring two new green roof retrofit developments. This project is funded under the City of Melbourne ‘Green Our Rooftop’ initiative, and uses a large new green roof retrofit that is set to be constructed on 1 Treasury Place in Fitzroy, as well as the innovative Melbourne Skyfarm that will replace the top level of the Siddeley Street Carpark in Docklands.

Monitoring a green roof retrofit before and after its construction is an ideal way to answer some of the tricky questions about the secret life of rooftop animals. For example, we don’t yet fully understand the value of a single roof, the primary pathways by which animals come to live or forage on a roof, and whether there is any movement of animals between rooftops.

It is often not acknowledged that some invertebrates (like spiders and flies) and some birds (like the Peregrine Falcons nesting on 367 Collins St) are capable of using bare roof spaces. Knowing this baseline of buzzing activity helps us know what animals have been attracted after a green roof is installed. This allows us to quantify the added value of a new green roof in the landscape.

It is likely, however, that the construction of a green roof is so disturbing and prolonged for a site that it might wipe the slate clean. This is where monitoring the site immediately after construction is important – it tells us the first-comers, and potentially highlights stowaways that have been transported onto the roof with the plants or in the soil. Perhaps surprisingly, snails have been found in large quantities on some green roofs, many stories high – likely as a result of hitch-hiking on plant material during roof installation.

We will also monitor nearby ground sites that might act as sources of animals that appear on the new green roofs. This may also show whether anything that is transported onto the roof might spill over into adjacent environments. Often soils and plants used in green roof construction come from far away, and can create assemblages of species that are atypical of the regional area. Finally, monitoring adjacent roof sites helps answer whether there is any spill over effects that might generate synergistic or additive effects of multiple green roofs popping up in the landscape.

During our study we will also be recording specific plant-insect interactions so we can not only know what insects are up on the roof, but what they are using it for. Pre-covid lockdown we had just finished collecting the baseline data to show what’s happening before the roofs have been constructed. Not surprisingly there wasn’t much happening on the bare roofs except for a few spiders and flies, whereas ground sites were still bustling with summer insect life.

At the end of our study we hope to know a little more about what makes a green roof good for biodiversity. Importantly, we want to avoid making roofs that act as “ecological traps” by enticing animals to live there without adequately fulfilling their life-cycle needs. Already we know that some ground nesting birds, whose nestlings are left to fend for themselves after hatching, find low reproductive success on green roofs. Solitary bees also struggle to produce viable offspring on roofs above 5 stories high. So, how do we create green roofs that provide the right resources, especially for breeding? To stay tuned follow the ICON blog or follow me on Twitter @CityKat75

References:

Baumann, N. (2006) Ground-nesting birds on green roofs in Switzerland: Preliminary observations. Urban Habitats 4 (1), 37-50.

MacIvor, J.S. (2015) Building height matters: nesting activity of bees and wasps on vegetated roofs. Israel Journal of Ecology & Evolution (ahead-of-print), 1-9.

Madre, F. et al. (2013) A comparison of 3 types of green roof as habitats for arthropods. Ecological Engineering 57, 109-117.

Williams, N.S. et al. (2014) Do green roofs help urban biodiversity conservation? Journal of Applied Ecology 51 (6), 1643-1649.

Shafique, M. et al. (2018) Green roof benefits, opportunities and challenges – A review. Renewable and Sustainable Energy Reviews 90, 757-773.

What difference do protected areas make on vegetation extent and condition?

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Logging road in Central Kalimantan, Indonesia. Photo by Roshan Sharma.

Biodiversity is the variety of all life forms on Earth and underpins the health of our planet. It provides important ecosystem services like food and fibre that are the basis of human existence. However, exploitative human activities on Earth have created an unprecedented breakdown of the environment, causing global biodiversity loss at an unprecedented rate and scale. Land cover change, mainly the conversion of vegetation – the state and processes that support biodiversity – is by far the most important driver of biodiversity loss. This conversion is led by the expansion of croplands, urban areas, infrastructure, logging, mining and fire (Curtis et al., 2018). 

The establishment of protected areas (PAs) is one of the most important and globally applicable approaches to reducing these conversions. PAs are clearly defined geographical areas that limit human activities in prescribed areas. Since the campaign to expand PAs in the World’s Park Congress in 1982, nations have strived to increase the extent of land under protection. The global PAs have grown to cover more than 28.4 million square kilometres or around 13 per cent of the Earth’s land surface (UNEP-WDPA, 2019). Further, the Convention on Biological Diversity (CBD) has called to increase the protected area state to 17 per cent of the Earth’s land surface (Aichi Target 11). 

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With the vast areas of land already under protection and calls to increase it, are PAs making a difference? PAs are known to be disproportionately established on marginal lands with least pressure of conversion and places unimportant for biodiversity. This means that PAs may not be having the intended impact – a reason many have criticised them. To understand the difference a PA is making, the outcome after the PA has been implemented needs to be compared with what would have happened without the PA in place (referred to as the counterfactual scenario). Estimating the counterfactual is the crux of finding such a difference or impact. However, estimating counterfactuals can be difficult due to the non-random allocation of PA. Evaluations that fail to accurately estimate the counterfactuals without considering non-random allocation of PAs and other spatial processes will cause bias and result in invalid estimates of impact.

This issue intrigued ICON Science PhD candidate Roshan Sharma, who started searching for literature for impact evaluation studies on PAs. He found that the literature is largely scattered, varied, and in many cases contradicting regarding how much difference PAs were making. There was a clear research gap that needed to be addressed.

Roshan decided to conduct a systematic review to address this research gap. Systematic reviews can be a great approach to synthesising evidence and generating higher quality evidence than individual studies. If done correctly, these reviews can allow researchers to come closer to understanding the true effect of an intervention. 

In an effort to increase the transparency and reproducibility of the review, Roshan developed a protocol with the help of ICON Science peers Ascelin Gordon and Marco Gutierrez, and fellow researchers from the University of Helsinki, the University of Western Australia, the University of Cambridge, and James Cook University. The protocol follows the Collaboration for Environmental Evidence guidelines and ROSES (RepOrting standards for Systematic Evidence Synthesis) reporting framework. Following the standard guidelines and frameworks ensures that the review covers all relevant literature, implements a dual consistency checking in screening and data extraction to remove reviewer bias, has a quality appraisal of all selected studies, and synthesizes only high-quality studies. Publishing the protocol ensures the results of the review will be published regardless of the findings, effectively removing publication bias. The protocol has been recently published in Environmental Evidence and can be found here

Now that the protocol has been published, Roshan and the team will be moving forward to undertake the review. They hope the results of the review will be useful for the larger scientific community and policymakers. There is an ongoing debate on whether the successor of Aichi Target 11 will be on setting higher area targets for PAs or emphasize more on impact measures. Thus, they hope that their findings will be relevant to the development of new post-2020 CBD targets. 

References

Curtis PG, Slay CM, Harris NL, Tyukavina A, Hansen MC. Classifying drivers of forest loss. Science. 2018. http://dx.doi.org/10.1126/science.aau3445

Sharma, R., Eklund, J., Barnes, M. et al. The impact of terrestrial protected areas on vegetation extent and condition: a systematic review protocol. Environ Evid 9, 8 (2020). https://doi.org/10.1186/s13750-020-00191-y

UNDEP-WDPA. The world database on protected areas. 2019.

How satisfied and motivated are landholders with conservation covenants?

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Landholders who have a conservation covenant on the title of their property (sometimes known as “covenantors”) have taken on the responsibility of managing their land for nature.

As with many things, the enthusiasm of landholders to continually manage their land in ways that benefit biodiversity is driven in large part by why they got involved in the first place, and stay involved (their motivations) and how satisfied they are with participating (satisfaction).

Following a similar study in South Africa, our group has helped develop and send out a survey on motivations and satisfaction to covenantors across Victoria, New South Wales and Tasmania, in conjunction with members of the Australian Land Conservation Alliance. It is part of a broader initiative to better understand how landholders feel about participating in private land conservation initatives, and will help guide the development of these programmes.

A summary of the results will be made available early next year, so stay tuned…

Oh, and if you are a covenantor in NSW, Victoria or Tasmania and you have been sent a link to the survey, we politely urge you to fill it out and have your say!