It’s no secret that human development frequently comes at a cost to other creatures. As our urban footprint expands, native habitat contracts. To compensate for this, most Australian governments require developers to invest in biodiversity offsetting, where habitat is created or protected elsewhere to counterbalance the impact of construction.
Although biodiversity offsetting is frequently used in Australia – and is becoming increasingly popular around the world – we rarely know whether offsets are actually effective.
That’s why we spent four years monitoring the program designed to offset the environmental losses caused by widening the Hume Highway between Holbrook and Coolac, New South Wales. Our research has found it was completely ineffective.
The roadworks required the removal of large, old, hollow-bearing trees, which are critical nesting sites for many animals, including several threatened species. To compensate for these losses, the developer was required to install one nest box for every hollow that was lost – roughly 600 nest boxes were installed.
Many of the boxes were specifically designed for three threatened species: the squirrel glider, the superb parrot and the brown treecreeper. We monitored the offset for four years to see whether local wildlife used the nest boxes.
We found that the nest boxes were rarely used, with just seven records of the squirrel glider, two of the brown treecreeper, and none of the superb parrot. We often saw all three species in large old tree hollows in the area around the boxes we monitored.
Even more worryingly, almost 10% of the boxes collapsed, were stolen or otherwise rendered ineffective just four years after being installed. Perversely, we found that invasive species such as feral bees and black rats frequently occupied the nest boxes.
It’s worth noting that research supports using nest boxes as a habitat replacement. However, they may never be effective for species such as the superb parrot. It’s not quite clear why some animals use nest boxes and others don’t, but earlier monitoring projects in the same area found superb parrots consistently avoid them.
Still, concrete steps can – and should – be taken to improve similar offset programs.
First, the one-to-one ratio of nest boxes to tree hollows was inadequate; far more nest boxes needed to be installed to replace the natural hollows that were lost.
There also was no requirement to regularly replace nest boxes as they degrade. It can take a hundred years or more for trees to develop natural hollows suitable for nesting wildlife. To truly offset their removal, thousands of boxes may be required over many decades.
Second, nest boxes clearly cannot compensate for the many other key ecological values of large old trees (such as carbon storage, flowering pulses or foraging habitat). This suggests that more effort is needed at the beginning of a development proposal to avoid damaging environmental assets that are extremely difficult to replace – such as large old trees.
Third, where it is simply impossible to protect key features of the environment during infrastructure development, more holistic strategies should be considered. For example, in the case of the woodlands around the Hume Highway, encouraging natural regeneration can help replace old trees.
Tree planting on farms can also make a significant contribution to biodiversity – and some of these may eventually become hollow-bearing trees. A combination of planting new trees and maintaining adequate artificial hollows while those trees mature might be a better approach.
When an offset program fails, it’s unlikely anyone will be asked to rectify the situation. This is because developers are only required to initiate an offset, and are not responsible for their long-term outcomes.
In the case of the Hume Highway development, the conditions of approval specified that nest boxes were to be installed, but not that they be effective.
Despite the ecological failure of the offset (and over A$200,000 invested), the developer has met these legal obligations.
This distinction between offset compliance and offset effectiveness is a real problem. The Australian government has produced a draft policy of outcomes-based conditions, but using these conditions isn’t mandatory.
The poor results of the Hume Highway offset program are sobering. However, organisations like Roads and Maritime Services are to be commended for ensuring that monitoring was completed and for making the data available for public scrutiny – many agencies do not even do that.
Indeed, through monitoring and evaluation we can often learn more from failures than successes. There are salutary lessons here, critical to ensuring mistakes are not repeated.
David Lindenmayer, Professor, The Fenner School of Environment and Society, Australian National University; Martine Maron, ARC Future Fellow and Associate Professor of Environmental Management, The University of Queensland; Megan C Evans, Postdoctoral Research Fellow, Environmental Policy, The University of Queensland, and Philip Gibbons, Senior Lecturer, Australian National University
Unfortunately, we’re probably underestimating the impact that fishing is having on ray populations. Although some will survive capture, we know little about the non-lethal and long-term effects of that stressful experience.
Included in those unknowns are questions relating to reproduction. In particular, what if the captured ray was pregnant? Would she still give birth? If she did, would her offspring survive?
This research focused on the southern fiddler ray (Trygonorrhina dumerilii), also known as the “banjo shark”, a species common in the coastal waters of southern Australia.
Beyond just this species, our results suggest it’s possible that other ray and shark species that have live-birth (including most large sharks) could be similarly affected.
All rays give birth to live young. For many species pregnancy lasts about a year, making them more likely to be captured during reproduction compared to egg-laying species.
Pregnant southern fiddler rays were collected by hand in Swan Bay, Victoria, Australia, using SCUBA to minimise stress during collection. They were transported and housed in our “maternity ward” – a large outdoor research facility located nearby.
Our maternity ward included a large tank equipped with a giant paddle that pushed water past stationary nets, thereby simulating a trawl net being dragged by a boat. Rays were placed in these nets and trawled, followed immediately by 30 minutes of air exposure to replicate the process of sorting the catch on board a boat. A similar number of control females were kept in a separate tank and were not subjected to trawling or air-exposure.
Over the next three months, pregnancy and the health of each mother was regularly monitored via ultrasounds, blood-sampling and weighing. At birth, their pups were also measured for length, weight and had their blood sampled. Mothers carried and gave birth to an average of two pups.
Pups from trawled mothers were 12% shorter and 27% lighter than those from untrawled mothers.
In most animals undersized offspring generally have a lower chance of survival. Marine predators are often restricted in their options of potential prey by the size of their mouth, with smaller animals more easily consumed.
Lower body mass may mean pups have fewer energy reserves – in the form of an internal yolk sac – to rely on. An increased risk of starvation is possible during the early stages of life when inexperience can make catching prey difficult.
Pups from trawled mothers also showed signs of a stress response in their immune system, and increased vulnerability to infection and disease is possible. The increased energy needed to maintain a healthy immune system may also limit growth rates. This is important for female fertility because larger females tend to carry more offspring.
Trawled mothers showed indicators of stress for 28 days after trawling, exhibiting elevated immune responses and 9-15% lower body weights compared to their unstressed counterparts.
Reduced body condition after giving birth could mean that the next mating event may be delayed or missed in order to rebuild sufficient energy stores for a successful pregnancy.
Delaying or missing mating opportunities could be particularly important for other live-bearing species like the scalloped hammerhead (Sphyrna lewini) and sharpnose sharks (Rhizoprionodon taylori), which mate again shortly after giving birth.
By examining the non-lethal responses to capture stress, we’re working towards more efficient fishing practices that improve conservation outcomes for marine species.
Regarding reproduction, it may mean that we can better assess and manage fishing practices in areas where sharks and rays are known to congregate and breed. Fishing techniques that reduce the amount of accidental capture of rays and sharks will benefit both fishermen and conservation efforts, especially during vulnerable breeding periods.
For example, “turtle exclusion devices” in trawl nets (originally designed to prevent the capture of sea turtles) allow animals that are much bigger than the target catch to escape through a chute. Such a device may be suitable for reducing shark and ray bycatch too.
Our study into how capture affected pregnancy in rays is part of a larger research program led by Monash University in collaboration with Flinders University, University of Tasmania and the Victorian Marine Science Consortium. The research program’s results on both lethal and non-lethal outcomes of capture have helped inform the Australian Fisheries Management Authority (AFMA) how to fish for the future and improve the conservation of sharks and rays.
Half of the world’s people now live in urban areas. This creates competition for resources and increases pressure on already limited green space.
Many urban areas are still experiencing active degradation or removal of green space. To reverse this trend and ensure the multiple benefits of green space are realised, we urgently need to move toward on-ground action.
However, there is no clear guidance on how to translate the evidence base on green space into action. There is limited information to guide green-space practitioners on how much is “green enough”, or on how to manage and maintain green space. There is also a lack of guidance on how to deliver the multiple benefits of green space with finite resources.
A recent World Health Organisation (WHO) report aims to provide guidance on how to tackle the uncertainties of providing such spaces.
There is a substantial evidence base to show that green space is good for us. It is associated with many health benefits, both physical and mental – including reductions in illness and deaths, stress and obesity – and a range of positive social, environmental and equity outcomes.
Providing adequate green space within our urban areas is therefore paramount. We need to preserve, enhance and promote existing green spaces and create new spaces.
Various political frameworks underscore the need for these spaces in our cities. For example, the New Urban Agenda calls for an increase in safe, inclusive, accessible, green and quality public spaces. The 2030 Agenda for Sustainable Development pledges to:
… provide universal access to safe, inclusive and accessible, green and public spaces, in particular, for women and children, older persons and persons with disabilities.
The WHO report carried out a systematic review of the published evidence on green-space interventions. The review found a variety of intervention types have strong evidence for delivering a range of health, social and environmental outcomes.
These intervention types range from smaller green spaces, such as street trees and community gardens, to larger, more interlinked spaces, such as parks and greenways. This signals the need to think beyond the traditional urban park when considering how to meet the demand for green space among growing urban populations.
Another finding of the review was that urban green-space interventions seem to be most effective when a physical improvement of the space is coupled with social engagement.
This highlights the importance of understanding the intervention’s target audience. Sufficient time and resources must be devoted to engaging with this audience. This should happen both during the design and implementation phases and when the intervention is completed – and promoted.
The WHO report compiled case studies of urban green-space interventions from across Europe, and documented the common lessons from these.
This unearthed a range of findings. For example, fostering multidisciplinary and cross-sectoral collaborations during planning, implementation and evaluation is a key factor in creating a successful green space.
Another key finding was the importance of understanding that urban green-space interventions are long-term investments. They therefore need to be integrated within local development strategies and frameworks – such as urban masterplans, transport policies and sustainability and biodiversity strategies.
An example of an urban green-space intervention that showcases good practice, and which features as a case study in the WHO report, is the Connswater Community Greenway in Northern Ireland. This project adopted a bottom-up approach and emphasised community engagement. A full-time community support officer was employed.
Having public engagement embedded from the start ensured the local community’s needs were well understood. The intervention’s design was responding to these identified needs.
Coupling this local understanding with the latest thinking on good practice led to an evidence-based design that was fit-for-purpose in the local context.
The project was also understood to be a long-term investment. A 40-year management and maintenance plan for the greenway was developed from the outset.
The WHO report represents an important step forward. As worrying trends in mental ill-health, obesity, social isolation, health inequalities and environmental degradation grow globally, there is a pressing need to implement equitable solutions – and green space has a key role to play in this.
Urban green-space interventions can deliver health, social and environmental benefits for all population groups – particularly among lower socioeconomic status groups. There are very few – if any – other public health interventions that can achieve all of this.