For each mesh block zoned as residential, we tallied up the total area zoned as parkland within a 5-kilometre radius. The results are shown in the interactive map below, in which darker greens indicate a larger area of available parkland (very light green: 0-4.5 sq km; light green: 4.5-9.2 sq km; mid-green: 9.2-13.2 sq km; dark green: 13.2-19 sq km; very dark green: more than 19 sq km).
Of the 42,199 residential mesh blocks currently under stage 4 restrictions, 3,496 have between 0 and 4.5 square kilometres of parkland within 5km. This equates to about 135,000 homes or 340,000 people with little or no access to parks within their permitted area for exercising.
On average, residents in Cardinia, Mornington Peninsula and Melton have the least parkland within a 5km radius, whereas those in Knox, Yarra and Banuyle have the most.
Haves and have-nots
Our findings confirm that some Melburnians are more fortunate than others in their ability to access urban green space during stage 4 lockdown.
For those less fortunate, the state government should consider replacing the blanket 5km rule with a special provision that allows people to travel outside this radius if they would otherwise be unable to access a park.
Bespoke rules could also help others, such as residents with a disability or older Melburnians who use a mobility aid. While many members of these groups might have plentiful parks within their 5km radius, they may have problems accessing them. Issues can include uneven pavements, kerbs without ramps, or steeply sloped paths.
The state government could help these people by auditing public spaces to establish where structural barriers exist, and then work to remedy them. Alternatively, once again, the blanket 5km rule could be amended with a special provision that allows older Melburnians, or those with a disability, to travel outside their 5km radius to get to the most suitable nearby park.
Melbourne’s existing water supplies may face pressure if global warming hits the 2℃ level, according to our new research published today in Environmental Research Letters.
The effects of drying and warming in southern Australia are expected to reduce natural water supplies. If we overshoot 2℃ of warming, even the desalination plant might not provide enough drinking water to a growing population.
However, keeping warming to 1.5℃ would help avoid many of these negative consequences. This brings home the local benefits of acting swiftly to limit global warming. Luckily, there are options available to secure our water supply.
Warming and drying effects
The Earth has warmed by about 1.1℃ since pre-industrial times, causing ongoing global changes to our atmospheric composition. The Paris Agreement commits the world to holding the increase to “well below” 2℃, and “pursuing efforts” to limit the increase to 1.5℃.
While we’re confident there will be more hot extremes and fewer cold extremes as global temperatures rise, the consequences of further global warming for other climate extremes – such as drought – in different parts of the world are harder to pinpoint.
Most Australians recall the severity and length of the Millennium Drought. This event severely stressed agricultural and natural systems, and led to the commissioning of desalination plants in the five largest cities in Australia, at a cost of several billion dollars.
Desalination offers an important lifeline. Although it comes with high short-term costs, it supplies vital water security over the long term. Successful efforts to improve water-use efficiency have reduced per capita demand rates, but growing populations in major centres will lead to increasing water demand.
Right now, large parts of southeastern Australia are in the grips of another drought. Although drought is a common natural feature of Australia’s climate, in recent decades we have observed long-term drying trends over much of southern Australia.
Currently, all capital city urban reservoir systems in southern Australia are below 60%, and several are nearing or below 50%. The Victorian government recently ordered 125 gigalitres of water from the desalination plant.
With these challenges in mind, our paper explores the effects of future climate change on the surface water supply infrastructure for Melbourne.
Climate models and hydrological models together indicate future declines in catchment inflows as global warming increases from 1.5℃ to 2℃. The good news is when desalination is added to the mix, which it is, pressure on our water storage is dramatically reduced. However, population growth and climate change remain key challenges into the future.
The buffer is shrinking
The take-home message is, if global warming approaches 2℃ and beyond, the combined impacts of climate change and population growth will ultimately begin to outstrip the buffer desalination provides for us without ongoing investment in water security. Fortunately, desalination plants, storm water, water recycling and continuing to improve efficiency are all viable options.
To ensure our water security, and with it, the safety and prosperity of the urban centres which are the engine houses of the Australian economy, we all need to be vigilant in managing water resources.
We also all need to play an active part in the global effort to reduce the impacts of climate change. The commitments by the world’s nations for the 2020-30 period remain insufficient to achieve the temperature goals. Global emission rates continue to rise, and atmospheric greenhouse gas concentrations are steadily accelerating.
The task of turning around our emissions in time to avert many of the serious impacts of climate change is becoming ever more implausible. In the coming 10–20 years, we expect to shoot past 1.5℃.
With so much momentum in both human and natural systems it is becoming increasingly unlikely that we will avoid warming beyond 1.5℃. However, if we can achieve it, the list of benefits includes greatly reduced stress on the water supplies we rely on for our very existence.
Continued logging in Melbourne’s water catchments could reduce the city’s water supply by the equivalent of 600,000 people’s annual water use every year by 2050, according to our analysis.
We calculated water lost due to logging in the Thomson Catchment, which is the city’s largest and most important water supply catchment. Around 60% of Melbourne’s water is stored here.
Since the 1940s, 45% of the catchment’s ash forests (including mountain and alpine ash forest) have been logged. There are plans to log up to a further 17% of these forests under the VicForest’s existing logging plan.
Past logging in the ash forests has reduced the Thomson Catchment’s water yield, which is the amount of water that flows through the catchment, by 15,000 megalitres (a megalitre is a million litres) each year. This equates to around 9% of water yield from ash forests across the catchment.
By 2050, continued logging in these forests at the current rates could increase this loss to 35,000 megalitres each year, or 20% of water yield. This will be equal to the water use of around 600,000 people every year, based on estimated water use of 161 litres per person each day.
The city of Melbourne has some of the best quality water in the world. A key reason for this is that the city’s first water infrastructure planners closed many of the key water catchments to intensive human disturbance, such as logging.
But there also can be competition for water between different land uses in catchments that are not closed and open to logging. Indeed, it has long been known that logging can significantly reduce the amount of water produced from forests, especially thoseclose to Melbourne.
Research on forest hydrology shows that the amount of water yielded from ash forests is related to forest age. Catchments covered with old-growth ash forests yield almost twice the amount of water each year as those covered with young forests aged 25 years. This is because evapotranspiration, the process by which trees transpire water into the atmosphere as well as evaporation from the surrounding land surface, is higher in young forests compared with older forests.
Up to 200,000 trees per hectare germinate following logging or an intense fire which burns the whole stand. Intense competition between young trees results in rapid growth rates along with increased evapotranspiration. As the forest matures, the trees thin out, and after 200 years, an ash forest can have less than 50 trees per hectare. These older ash forests release more water back into the catchment.
With logging occurring every 60-120 years, large areas of ash forest are kept in a high evapotranspiration stage of growth, therefore releasing less water back into the catchment.
Perhaps the losses in water yield could be justified if the value of the timber and pulpwood produced from logging exceeded the value of water. However, previous research has shown that the water in these areas is 25.5 times more valuable than the timber and pulpwood from ash forests.
What can the Victorian government do?
The ash forests in the Thomson Catchment are logged primarily for paper manufacturing. Under the Forest (Wood Pulp Agreement) Act 1996, the Victorian government is bound to supply Australia’s largest pulp and paper mills at Maryvale, owned by the Nippon Paper Group, with at least 350,000 cubic metres of native forest logs each year. The Thomson Water Supply Catchment is allocated for logging under this Act.
If logging was stopped in the catchment, what is the alternative for these paper mills? The answer is to source wood from current plantations. In 2017, Victoria produced 3.9 million cubic metres of logs from plantations. This could supply the pulp and paper mills at Maryvale several times over.
A challenge facing Victoria’s forest industry is the loss of jobs. One major factor in this is out-of-state processing. Australia tends to import lower volumes
of more processed and higher value wood products, including printing and writing paper. By contrast, higher volumes of less processed and lower value wood products, such as woodchips and unprocessed logs – largely from plantations, are exported.
Redirecting plantation sourced logs and woodchips from export markets to domestic processing can address some of these problems. In fact, detailed analysis suggests doing this would have an overall positive economic impact for Victoria.
Stopping logging in the Thomson Catchment and sourcing instead from well managed plantations could both boost water supply and create more jobs. Of course, some jobs would be lost for people who log from the catchment, but this would be more than compensated for by employment in the plantation processing sector.
The first Wood Pulp Agreement Act of 1936, which legislated supply of pulplogs from Victorian state forest to earlier paper manufacturers in Maryvale, featured a clause stating logging was to cease following the designation of the Thomson Catchment in 1967. This has clearly not occurred. In fact 63% of logging in the ash forests across the catchment has occurred since 1967.
The Thomson Catchment is the only one of Melbourne’s large water supply catchments open to logging. Given the critical importance of the Thomson Catchment, our work clearly indicates the Victorian government needs to cease logging and prioritise the supply of water to the people of Melbourne.
We found pharmaceuticals in every bug we sampled – over 190 invertebrates – from six different streams. These included caddisfly larvae, midge larvae, snails and dragonfly larvae. We also found pharmaceuticals in spiders living in stream-side vegetation.
We found 69 different drugs in the bugs, including fluoxetine and mianserin (anti-depressants), fluconazole (an anti-fungal), and non-steroidal anti-inflamatories (NSAIDs), often used to treat arthritis.
While we don’t know how these drugs are affecting these invertebrates, we know from other studies pharmaceuticals do affect the lifecycles of other organisms.
We also calculated that animals that eat these aquatic invertebrates, such as platypus, would be receiving half the daily recommended dose of anti-depressants for humans.
We know wastewater is a contributing factor to pharmaceutical contamination in aquatic organisms, so we sampled from a range of streams with different wastewater inputs. These included a site just downstream of large-scale wastewater treatment facility, and areas with ageing septic systems.
We also included a stream within a national park to attempt to obtain samples we thought would be free of pharmaceuticals. We sampled aquatic invertebrates and stream-side spiders and tested them for 98 pharmaceutical compounds.
To our surprise, we found up to 69 different pharmaceuticals in aquatic invertebrates and up to 66 in riparian (streamside) spiders. Contamination was greatest downstream of the high capacity waste water treatment plant.
Moreover, every insect we sampled contained pharmaceuticals, including at the site in a national park, possibly due to septic systems in the drainage area of the stream that contribute small amounts of waste water.
The fact we detected drugs, admittedly in very low concentrations, in this seemingly pristine site suggests finding places “free” from pharmaceutical contamination may be difficult. Recent studies by other researchers detected pharmaceutical contamination in surface water in Antarctica and in national parks in the US.
We also found spiders living on the stream edge (the “riparian zone”), also contain a wide variety of pharmaceuticals in their tissues. These animals primarily consume adult insects and are an indication other animals that eat adult aquatic insects, such as birds, reptiles and bats, may also be exposed.
The dark side of our pharmaceutical use
We take and are prescribed pharmaceuticals to improve our quality of life. These medications are designed to be biologically active – they are meant to treat us; for example, we take paracetamol to alleviate a headache. For all the benefits drugs afford us, there is an often overlooked dark side to our extensive use of them.
When we take a pharmaceutical, our bodies do not always use all of the drug and we excrete drug residues into our waste water and the drugs then move into our sewage system. Unfortunately, waste water treatment facilities are not always designed to, or are capable of, removing pharmaceuticals. So they’re often discharged into our streams, rivers and coastal waters.
We have known from many studies over almost two decades that the drugs we take are found in waterways around the world. There are thousands of drugs available, but very little is known about their occurrence and movement through aquatic food webs.
Our research team has previously studied the effects these pharmaceuticals have on organisms living in streams. For example, we found fluoxetine, a common anti-depressant, increased stream insect emergence (the important phase of an insects’ life where it metamorphoses from a stream dwelling larvae to an aerial adult).
Platypus and trout live in or nearby the streams we studied. These animals feed almost exclusively on aquatic invertebrates. Although we did not directly sample trout or platypus, we were able to use previous studies on the feeding rates of these animals to estimate what proportion of a human daily dose of drugs they may be exposed just by eating the aquatic invertebrates we did measure in the streams we studied.
Based on these calculations, a platypus living in a creek receiving waste water could be exposed to over half of a human daily dose (per kg body weight) of antidepressants, just by eating aquatic invertebrates. Trout, too, would be exposed to these drugs, but would be exposed to a lower dose.
Studies have shown single drugs can alter the behaviour of fish, but just what consuming 69 different pharmaceutical compounds might do to a fish or platypus remains unknown and worthy of future research.
Global pharmaceutical use is increasing, with many benefits to humankind. However, our recent publication makes it clear pharmaceuticals are accumulating and moving through stream food webs and expose spiders, and likely birds, bats, fish, and platypus to a wide array of drugs. We are yet to fully understand the broader ecological consequences of this type of pharmaceutical contamination.
We know in humans, there are health risks associated with taking multiple drugs because of drug interactions. Is the same true for animals? Like so many studies, our research leaves us with many unanswered questions.
The one thing that is abundantly clear is the drugs we so frequently use are ending up in nature and are moving through food webs.
This article was co-authored by Emma Rosi, an aquatic ecologist at the Cary Institute of Ecosystem Studies.
Spectacular images of recent volcanic eruptions in Hawaii are a little disheartening – especially given news reports suggesting there is a sleeping volcano under Melbourne that could awaken and erupt at any moment.
Understanding the geological differences between Melbourne and Hawaii is really helpful in working out how we can keep an eye on future risks in Australia.
Victoria and South Australia do host an active volcanic field, called the Newer Volcanics Province (NVP). This is not a single volcano with a large single chamber of molten rock (magma) — the common image of a volcano — but a widespread field of multiple small volcanoes, each with a small volume of magma.
Melbourne lies at the eastern end of the NVP, and the most recent eruptions in this area occurred over a million years ago.
Mt Gambier in southeastern South Australia represents the western margin of the volcanic field and the most recent eruption — only 5,000 years ago.
Between Melbourne and Mt Gambier there are more than 400 small volcanoes that erupted over a period of 6 million years.
The NVP was most active between 4.5 million to 5,000 years ago and volcanologists consider the field to still be “active” with the potential for future eruptions.
We do not know when the next eruption will take place.
The NVP is located within a tectonic plate – and not along a plate edge like the Ring of Fire volcanoes (for example, Mt Agung on Bali).
Tectonic plates are large slabs of rock made up of the Earth’s crust and uppermost part of the mantle (the lithosphere) which form the outer shell of the Earth, and move around slowly relative to each other.
While Kilauea volcano in Hawaii is also located within a tectonic plate, it has several key differences with the NVP in Southeastern Australia.
Magma source and volume
While Hawaii sources large volumes of magma from deep within the Earth, the NVP only receives small amounts of magma from just below the Earth’s crust.
It’s worth noting here that the makeup of the magma is similar in both locations, with both erupting runny basalt – a type of rock low in silica, and high in iron and magnesium.
We suspect that in Australia’s NVP, magma can move very fast from its source to the surface (on a time scale of days). This can bring rock fragments of the mantle (xenoliths) to the surface as the magma moves too fast for them to melt.
Hawaiian volcanoes can erupt numerous times, but NVP volcanoes are largely monogenetic — that is, each only erupt once or over a restricted period of time.
Hawaii is located on the oceanic crust of the Pacific Tectonic Plate, which is a thin (around 7 km) layer of material that is dense and rich in iron. The magma can rise through this crust quite easily.
In contrast, the NVP is located on continental crust which is much thicker (about 30km), richer in silica and much less dense. Magma finds it much harder to travel through this kind of material.
The explosivity of a volcanic eruption can depend on availability of water.
“Dry” eruptions – where magma has little-to-no interaction with ground water or water on the Earth’s surface – typically produces mildly explosive eruptions such as lava fire fountains, showers of lava fragments and lava flows.
The most explosive, hazardous eruptions form where rising magma interacts with ground water, surface water or sea water. These “wet”, (phreatomagmatic) eruptions can produce deadly, fast moving, ground-hugging currents of gas and volcanic material – called pyroclastic surges, and send abundant fine volcanic ash into the atmosphere.
The Australian Mt Gambier eruption 5,000 years ago was a “wet” eruption, and had a volcanic explosivity index of 4 on a scale of 0-8 (where 0 represents a lava eruption, 1 a spectacular lava “fire” fountain as recently witnessed in Hawaii, and 8 represents a catastrophic explosive super-eruption).
The accompanying ash column is estimated to have reached 5km to 10km into the atmosphere.
On Hawaii explosive eruptions are rarer because the magma has a low gas content and groundwater aquifers are not as large as in the NVP. However, when lava flows into the sea there are often phreatic or steam explosions which can be hazardous to nearby spectators.
Another important factor relates to how we keep an eye on volcano risk at the two sites. Kilauea on Hawaii is extremely well monitored, and tracking magma moving underground has helped predict eruptions.
In contrast, the NVP is less well monitored, likely because there is no present volcanic activity, and it’s a huge region.
However, warning signs of an eruption are likely to be similar in the NVP to those on Hawaii – small earthquakes, minor uplift and/or subsidence of the ground, changes in ground temperature and gas or steam rising out of the ground.
damage to machinery and electricity infrastructure by infiltrating ash
respiratory problems for people prone to asthma, and
disruption to air traffic across southeastern Australia due to drifting ash clouds driven by prevailing south-westerly winds.
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Further scientific research is required on active volcanic fields such as the NVP to know how fast magma travels from its source to the surface, how much warning we might have before an eruption, and how long an eruption and its impacts might last.
Melbourne and Adelaide have been most prone to deadly heatwave conditions among Australia’s five largest cities, according to my new research published in Climatic Change.
My study shows that between 2001 and 2015, Melbourne and Adelaide suffered the most exposure to temperatures beyond a crucial threshold of 7.26℃ above the average. Above this threshold, deaths are more likely because people are not acclimatised to the extreme weather.
I estimated that there were 151 deaths in Melbourne and 144 in Adelaide due to extreme heatwaves – those above this 7.26℃ threshold – between 2001 and 2015.
Heatwaves can cause significant numbers of deaths, especially among vulnerable groups of people who are not prepared for or acclimatised to extreme hot temperatures.
Even though Melbourne and Adelaide are located in more temperate areas (in comparison with more northerly cities such as Brisbane), they have been periodically hit by severe heatwaves.
In my research, I looked at the “Excess Heat Factor”, a measure used by the Bureau of Meteorology as part of its heatwave forecasts. It is the difference between the 3-day average temperature and the 30-day average, and is therefore a measure of how “unusually hot” it is during a heatwave. It captures how much residents are likely to struggle to cope with the heat.
The graphs below show the frequency of excessively hot or cold weather for each of Australia’s major cities from 2001 to 2015. These charts show that most days had temperatures where the 3-day average was 2℃ higher or lower than the 30-day average.
A grey dashed line shows the extreme heat threshold that my study found was associated with higher deaths, relative to moderately warm and cool days.
I then estimated the threshold at which there is a significantly increased risk of deaths.
The death rate (per 100,000 people) that coincides with the extreme heat acclimatisation measure is shown as a black line on each of the graphs. This is an average impact of temperature on death rates, adjusted for different cities’ population sizes and baseline death rates.
Between 2001 and 2015, most of the events above the 7.26℃ extreme heat threshold occurred in Adelaide, Melbourne and Perth. Brisbane and Sydney had fewer days above this threshold.
The importance of acclimatisation
Several previous studies have linked excessive heat to adverse events such as deaths (see here, here and here), and emergency department visits and ambulance call-outs (see here, here and here). But my study is the first to solely focus on the extreme heat index acclimatisation measure, and to identify a temperature threshold in this way. This measure is important, as it identifies the times when residents of cities with different background climates begin to struggle with the heat.
The Bureau of Meteorology does not currently use the 7.26℃ threshold identified in my paper. Doing so may improve predictions of which heatwaves are most likely to turn deadly for significant numbers of people living in our major cities.
Implications for policy
Since the severe heatwaves of 2009, many states and territories have implemented or revised their heatwave response plans, or conducted awareness campaigns to educate people about the health risks. But more can be done to make vulnerable people aware of upcoming heatwave events.
A 2016 review proposed that heatwave response plans and early warning systems should be evaluated and updated at least every five years, to ensure that they remain effective, and to incorporate up-to-date knowledge about population-level vulnerability to heat stress.
While my research has focused on Australia’s five largest cities, this does not mean that extreme heat is any less dangerous in other areas. Nor is the danger limited to prolonged heatwaves – individual hot days can catch people out too. A NSW study found that emergency hospital admissions due to dehydration and other heat-related injuries rose significantly on individual hot days, as well as during hot spells lasting at least three days.
This suggests that we need to develop more complex heat risk management plans, with targeted responses for different health issues based on the longevity of extreme heat events.
Implications for the future
We also need to consider the patterns of extremely hot temperatures that we are likely to encounter in the future. Recent research found that changes in the frequency and duration of heatwaves will be larger in the north of Australia than the south. But the same study also found that “heatwave amplitude” – the intensity of the hottest day of the hottest heatwave – will increase more in southern parts of Australia.
This research suggests that cities south of Brisbane will experience the most severe temperature spikes beyond what their residents are used to dealing with.
There are more and more of us on Earth, and increasingly we’re choosing to live in cities. This is a problem for wildlife: urbanisation is one of the greatest threats to biodiversity. Sprawling construction to accommodate people completely removes or modifies the homes of many other species.
But although we need to do all we can to mitigate these effects and their causes, cities are far from biodiversity wastelands. In fact, cities are home to large numbers of species, many of which are threatened.
One such example is the iconic but endangered southern brown bandicoot. New research has found these shy animals thriving in peri-urban areas (the interface between cities and more rural areas) on the outskirts of Melbourne.
Through our effects on the environment, humans are increasingly creating “novel ecosystems”: areas composed of new combinations of species and/or new and modified environmental conditions. In these areas there are winners and losers. How we perceive and manage such ecosystems could have a big influence on conserving species more broadly, and helping to address Earth’s extinction crisis.
Our goal was to see whether novel sites could support resident bandicoots. Crucially, could peri-urban areas allow bandicoots to breed, recruit (attract new migrating individuals) and survive well enough for populations to persist?
Don’t judge habitats by their appearance
Contrary to what the Human Threat Hypothesis (and logic) might predict, we found more bandicoots at novel sites (66 individuals recorded over 1722 trap-nights) than remnant sites (26 individuals recorded over 1384 trap-nights). And bandicoots were most abundant at the novel site with the most urbanised surroundings. The condition of females was similar between novel and remnant sites.
Most bandicoots at novel sites were resident (meaning they were observed at the same location multiple times thoughout the study). At these same sites we recorded successful breeding, recruitment of young adults, and survival of mature adults.
Our results challenge conventional conservation thinking. Where bandicoots did best is also where known predators such as foxes and feral cats are present and abundant, as opposed to the nature reserves from which they are largely absent. Remnant areas also have more intact native vegetation, whereas bandicoots in urban areas nested in roadsides full of invasive blackberry, a weed often targeted for removal.
Bandicoots like thick vegetation, but they appear not to care which plant species they use – as long as cover is sufficient. Blackberry bushes may protect bandicoots from predators, and also be a source of food through the insects they attract.
On the topic of food and just how adaptable bandicoots are, locals within our study region reported them dining on pet and domestic animal food from backyards.
Conservation opportunities in cities
A growing body of evidence suggests that even heavily modified environments can support viable populations of native plants and animals, and we should endeavour to manage these areas more sympathetically for the benefit of more species. This does not mean that all species will thrive in cities and heavily modified environments – there will always be a need for conservation reserves – but it throws the wilderness-versus-city dichotomy into question.
We need greater awareness of the nature we already share our cities with. Deliberate encouragement such as greener building and urban design that encourages wildlife to return and flourish would substantially benefit humans and other species alike. We are a part of and dependent upon nature, and as such should celebrate and seek to re-establish these vital connections.
The internet exploded recently with news that you can email trees in Melbourne. For the last two years, residents and visitors have sent thousands of emails to their favourite tree, particularly one much-loved golden elm.
“I see you every morning, watch you change with the seasons. It makes me happy knowing you are there,” emailed one resident.
At first glance, the idea of emailing a tree can seem a strange and wacky thing, but this email is one of thousands the City of Melbourne has received via its Urban Forest Visual which maps every public tree in the City.
The fact that Melburnians have embraced the notion of emailing a tree is no surprise. We have been passionate about trees in cities for a long time.
In 1871, a correspondent to Melbourne’s Argus argued that more trees were needed:
The beauty of the city, its coolness, its freedom from ground damp (which the trees would absorb), street currents of air, would all be enhanced; the expense and horrid ugliness of verandahs would be saved, and our taste would be complimented.
Our research explores the how people see and think about nature, sometimes trees and garden plants, but also weeds, “ferals”, and native plants and animals. This research shows consistently that nature is really important to people for many different reasons, and always in ways that differ from experts and professionals.
More trees in cities
Around the world, many cities have been undertaking massive urban tree expansion and renewal programs. Million Tree initiatives have begun in many cities including Los Angeles, New York and Shanghai. These aim primarily to plant more trees, but also manage the resilience of the forest by increasing species diversity, and encourage community participation in choosing locations and kinds of tree, and stewardship by adopting and caring for trees.
The City of Melbourne’s urban forest program is also using cutting-edge research to increase tree canopy cover, manage diversity in the forest, and reduce heat in summer. Yet it is perhaps through new ways of valuing trees, and through community engagement programs such as emailing a tree, that the City of Melbourne is being most innovative.
Why do we value trees?
By valuing, we mean determining the importance of trees. Trees have always been valued by urban people, but the way they have justified their value has constantly changed.
Some of Melbourne’s most frenzied tree planting occurred during the late 19th and early 20th century based on arguments that valued trees for “beautifying” the city, a concept that included improving human morality and mental health.
In recent decades, the emergence of the Ecosystem Services framework has allowed the benefits provided by trees such as temperature reduction, carbon sequestration and pollution interception to be quantified and valued in dollar terms. This thinking has led to recent initiatives such as the price-tagging of trees.
Yet the price of a tree tells us only a little about how important trees are to people. Recent community engagement work that we have been doing with the City of Melbourne using social psychology methods has identified multiple ways that the public values urban trees: for their contribution to civic identity, as nature, for their cultural heritage, to improve the community, and for their life sustaining properties.
It is clear that all these values need to be well represented in the urban forest to satisfy the community. This work has used a variety of methods such as questionnaires, value mapping, and photo sorts that have proven to be useful in helping the community understand the issues behind the urban forest program, and perhaps more importantly, to involve the community in decision making.
People’s emails to trees could provide some surprising insights into how people relate to trees, rather than just benefit from them. The emotional basis of this relationship is very strong (such as “I very fond of you [sic]”, “I miss you”, “It makes me happy knowing you are there”, and “It saddens me that your passing will be sooner than my own”).
Although the framing of trees as “ecosystems services” or “green infrastructure” are undoubtedly useful tools for directing the wheels of urban development, there is real power in understanding people’s emotional relationship with trees. Healthy, liveable and lovable cities need to allow people’s subtle and nuanced spiritual and emotional bond with trees to thrive.