How can we protect Auckland's environment - and the 1.4m people who live within it - in the face of urban intensification? In a series of upcoming free public talks, four of the University of Auckland's leading academics in this field will delve into the major problems facing the city - and how we might overcome them. They share some insights with science reporter Jamie Morton.

OUR TRANSPORT NETWORK

Each day, many of us make choices about how we get to work or school whether by car, bus, train, cycling or walking.

The cost, travel time, travel distance, individual mobility, and availability of a vehicle are some of the considerations that impact on choice.

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Walking and cycling are being promoted as sustainable transport choices and, with urban intensification, can be expected more often to become transport modes of choice.

Yet air pollution exposure is often higher for cyclists and pedestrians, due to the higher breathing associated with exercise.

"Road traffic accident risk has been identified as the number one barrier to cycling in a survey carried out a few years ago by Dr Judith Wang and colleagues at the University of Auckland," Associate Professor Kim Dirks said.

"Separate cycleways are being built around the city to help address this barrier.

"The other benefit is that they are also effective in reducing air pollution exposure by increasing the separation between cyclists and the tailpipes of cars."

As the city intensified, space was going to become more of an issue, forcing us to look at additional ways to ensure air pollution exposure was minimised.

Dirks said this was especially important, especially for active mode commuters, to ensure cycling and walking remained attractive and healthy options.

"While cycleways are expensive and not always possible due to space constraints, there are many much less expensive interventions that can also help," she said.

A young cyclist is silhouetted against the waterfront near the Auckland Harbour Bridge. Photo / File
A young cyclist is silhouetted against the waterfront near the Auckland Harbour Bridge. Photo / File

"For example, even modest physical barriers along roadways have been found to be effective at reducing air pollution exposure."

Dirks pointed out how the fenced segment along part of the Northwestern Motorway had been shown to reduce the air pollution exposure of cyclists travelling along the cycleway by about 30 per cent, compared to portions where there was no barrier.

"The construction of a barrier along the complete length of the cycleway would be a relatively inexpensive change which could considerably reduce the exposure of cyclists to air pollution."

But there was a lot that a person could do each day.

"Most people don't realise that walking on the side of the road opposite the main flow of traffic during rush hour can reduce their exposure by as much as 50 per cent, as can walking part of your journey through a park rather than along a busy road," she said.

"The changes can definitely add up, especially if the same route is travelled every day over an extended period of time, such as the journey to and from school and home for kids."

OUR WATERWAYS

The declining quality of our freshwaters is now among the most discussed and contentious issues in New Zealand.

A view toward Greenlane and Ellerslie from the slopes of Auckland's One Tree Hill. Photo / File
A view toward Greenlane and Ellerslie from the slopes of Auckland's One Tree Hill. Photo / File

"Nearly all our arguments about, our planning for, and our failures and successes in resolving our freshwater problem have revolved around farming and the footprint it has on the environment," freshwater ecologist Dr Kevin Simon said.

"There is good reason for this given the amount of our country that is farmland, its importance to us, and the environmental degradation that it can bring."

But there was, he said, a problem begging for solutions that was lost in amid the noise around issue.

"The streams in our cities are amongst our most polluted and undoubtedly the most difficult to fix.

"They are also the ones most of us interact with on a daily basis, whether we know it or not.

"Consider the sheer difference in the number of people and the amount and cost of physical infrastructure in an urban compared to a rural catchment and you start to the scope of the problem.

"The spatial extent of our cities may be small, but the problems we city-dwellers create are intense."

In our cities, we buried streams in pipes, we reshaped and moved them, and we stripped away the vegetation around them.

In 2013, Oruarangi Stream was polluted with thousands of litres of violet dye which entered the waterway from a bulk container in an industrial area near the Auckland Airport. Photo / File
In 2013, Oruarangi Stream was polluted with thousands of litres of violet dye which entered the waterway from a bulk container in an industrial area near the Auckland Airport. Photo / File

"We also flush them with stormwater and inject them with a vast array of chemicals ranging from hand soaps to illicit drugs," he said.

"Unsurprisingly, the ecological systems within them degrade and their threat to our health increases accordingly."

This so-called "urban stream syndrome" was a global phenomenon, and spreading as more people lived in cities, which had to grow and intensify to accommodate them.

"What is the remedy for this syndrome?

"Nobody knows yet, but there is growing recognition that we need to rethink how to build and live in our cities.

"Some of those changes are being made, but we are only scratching the surface of what is likely to be one of our most difficult freshwater problems."

OUR TREES

Whether we are sitting in the cool shade of majestic trees in Albert Park on a hot summer day, or strolling along tree-lined streets enjoying the beauty of spring blossom, trees enhance our wellbeing and day-to-day experience of city life.

The significance of trees in our city goes beyond the aesthetical, climate and environmental services they provide - their value also lies in the meanings we ascribe to them.

We can see this reflected in the vandalism and replacement of the lone tree on One Tree Hill or the extent to which neighbours will fight over the pruning or cutting down of individual trees.

But despite public support for tree-planting projects such as Mayor Phil Goff's Million Trees Programme, and our understanding of the value and importance of trees, increasing tree density in cities was "problematic", urban meteorologist Dr Jennifer Salmond said.

Firstly, opportunities for planting trees remained limited.

And secondly, urban trees did not necessarily provide benefits for everyone in all contexts.

"The same trees which provide shade and cooling in the summer may also promote damp, mouldy conditions in winter and increase heating costs," she said.

"Put simply, planting the wrong tree in the wrong place is likely to incur unnecessary cost and generate more harm than good."

Tree planting therefore needed to be carefully evaluated, Salmond said.

"The application of science in this field is in its infancy, and very few studies have sought to integrate understanding of the physical world with the social and cultural contexts of urban environments.

"Current research often emphasises a singular benefit and directs planners towards a single-variable optimisation strategy.

"This becomes problematic if we don't take into consideration the range of different outcomes and the multiple effects and potential trade-offs of tree planting."

For example, she said, the choice of male trees over female trees of the same species might reduce the mess from seeds and fruit on pavements - yet could result in health consequences from higher pollen loads.

In her presentation, Salmond will explore how we might approach understanding the value of trees in urban environments in different ways.

"I show how taking a holistic approach to evaluating the value of existing and future vegetation in a local setting can guide the choices we make about planting trees in the urban environment more effectively.

"In this way, we can learn to put the 'right tree in the right place' enabling urban trees to become an effective tool for urban planners and designers who are striving towards the development of resilient and resourceful cities in an era of climatic change."

OUR GREEN SPACES

Ecologist Dr Margaret Stanley said a big challenge was simply getting people to recognise that nature actually existed in cities, as did a colourful diversity of species.

"We need to be getting people to recognise that there is nature in cities - and all sorts of biota can and should live there," she said.

"We also need to make people aware of what's in cities now."

People often thought trees didn't belong in cities - whether it was because they were too shady, dropped leaves or ruined footpaths - and that people and homes should take preference over nature.

"Cities like Singapore have increased housing density and green space at the same rate," Stanley said.

A berm planted with corn on Kiwi Rd, Point Chevalier, in 2014. Photo / File
A berm planted with corn on Kiwi Rd, Point Chevalier, in 2014. Photo / File

"We need clever solutions, and new practices in planning and housing development.
"Landscaping should not be an add-on, but an integral part of it, to improve biodiversity and the health and wellbeing of the residents.

"We should integrate biodiversity and people - that means increasing biodiversity in our housing developments, being more strategic about our urban forest and get used to mixed-use spaces."

Encouraging people to value nature could be only as simple as finding their hook - more trees could reduce the impact of flooding, or improve mental health.

"And we should be getting people to value native species - can they recognise what are native species and why they are special?

"We should also be more accepting of untidiness, rather than mowing lawns within an inch of their lives.

"New Zealand can do it, we just need to think outside the box."

• Dirks, Salmond, Simon and Stanley will each host free one-hour lectures on their topics at the Owen G Glenn Building, at the University of Auckland's Business School in Grafton Rd, at midday on September 4, 6, 11 and 13 respectively. For more information, visit the website.