Why do we plant and remove urban trees?

Garden magazines 2What does the future hold for the urban forest? What is the urban forest? The term – like green infrastructure – suggests an integrated entity, perhaps collectively planned and managed. But most urban trees are in private gardens, not public spaces, and gardening is a personal, individualistic pastime, not a collective enterprise.

If the seeds of the urban forest are sown in a million home gardens, then we need to know how residents relate to garden trees. Let’s take a peek into the frontal lobes and back yards of our neighbours, and ask: why do we plant and remove urban trees?

A national study

In a series of new papers, Jamie Kirkpatrick, Aidan Davison and Grant Daniels from the University of Tasmania surveyed residents from Townsville to Hobart, to explore their motivations for planting and removing garden trees.

In one survey, over 650 residents filled out a questionnaire that listed over 40 reasons for planting and removing a tree. Respondents were asked to tick the reasons they agreed with. Reasons for planting a tree included: to improve the appearance of the house, reduce pollution, create a windbreak, and many more. Reasons to remove a tree included: to remove allergies or traffic hazards, to appease neighbours, and so on.

Why do we plant trees?

Brian the GardenerCan you guess the most popular response for planting a tree? Why do you plant trees in your garden? Before revealing all, let’s start at the bottom of the list, and grimace at the least popular responses.

Only 2% of respondents in the study indicated that they plant trees for ‘fashion’ or to ‘conform to social norms’. Producers of TV garden shows will shout with glee at this statistic, ‘Yes! We’re all individuals. Now for a word from our sponsors’. Regrettably, for every two residents who do acknowledge the existence of social norms, there’s one contrary prick keen to oppose them: 1% of respondents approved of planting trees to ‘displease the neighbours’.

So much for the misfits, what’s #1 on the list? The top two reasons are aesthetic: we love to plant trees for ‘beauty’ and to ‘improve the appearance of the garden’. Our next favorite rationale is environmental, to attract birds and animals, and the fourth is functional and personal: to create private spaces.

Why chop trees down?

Data from Kirkpatrick et al paper

The top five reasons for planting and removing a tree. From a survey of over 650 residents in eastern Australia. Based on Table 1 in Kirkpatrick et al. (2012).

The big reasons are obvious: trees grow tall, branches die, and bits fall off. The most popular reasons for removing trees relate to perceived risks.

Big trees create the most worry, as the authors of an earlier study noted, ‘Danger is often encoded in the size of the trees, or more specifically the relativities of size between the backyard and the trees’ (Head & Muir 2005, p. 90).

We can’t blame tree removal on ‘folks who aren’t like us’ either, as the ‘propensity to remove trees was not affected by city, income, gender, birth in Australia or otherwise and tertiary education or otherwise’ (Kirkpatrick et al. 2013, p. 172).

Gardeners who like indigenous plants – but not those keen to save exotic heritage trees – may be pleased that residents are more inclined to remove exotic than native trees: 59% of respondents supported the removal of environmental weeds, and 17% supported removal of exotic trees, but only 1% supported removing a tree simply because it is native. (Nevertheless, big trees are likely to be removed regardless of their origin).

Favouring form over function

The University of Tasmania study (like an earlier study) shows that suburbanites love garden trees.

By far the most common response [to an open ended question] was ‘the more trees the better’ in city environments, although a qualification about the importance of ‘the right tree in the right place’ was also common (Kirkpatrick et al. 2013, p. 169).

New home owners often remove old trees, especially exotics and environmental weeds like this old Camphor Laurel. Photo by Vanessa Berry, Source:Mirror Sydney.

New home owners often remove trees, especially exotics and environmental weeds like this old Camphor Laurel. Photo by Vanessa Berry, Mirror Sydney.

However we don’t love all trees, just some trees, in some places; and we remove the trees we don’t like with varying degrees of guilt and self-righteousness.

Quantitative studies like this show broad patterns and can obscure subtle complexities and variation between individuals. Most (if not all) respondents had many reasons for planting and removing trees. Nevertheless, the most popular reasons for planting a tree focus on beauty rather than practicality: ‘beauty is the outstanding perceived quality of garden and street trees’ (Kirkpatrick et al. 2012, p. 155). More people prefer to plant trees for flowers than for fruit or shade.

What about that urban heat island effect? Despite calls for more shady suburbs, many residents aren’t that keen on shady yards. Just over half of the respondents (55%) indicated that they would plant trees for shade. At the same time, 42% supported the removal of a tree if it ‘blocks light’ and 14% if it creates ‘excessive shade’. Many people probably ticked both boxes.

The eternally young urban forest

We urbanites are continually planting, removing and replacing trees. In the 5 years prior to the Kirkpatrick study, 70% of respondents planted a tree, 54% removed one, and most who removed a tree planted a new one. Based on these numbers, it’s easy to argue that we don’t have a problem getting trees into the ground. Many rural LandCare coordinators would kill for a 70% planting rate.

New plants in old spaces. Source:Guerrilla Gardening.

New plants in old spaces. Source: Guerrilla Gardening. Click on image for a larger view.

Nevertheless, the abiding feature of the urban garden is high turnover. By continually cutting and planting, we create an eternally youthful, ever-revolving urban forest. We ‘rejuvenate’ our gardens before trees grow old, and replace old big trees with new smaller species. We deny the influence of fashion and media, even though high turnover is embedded in the garden economy:

In the second half of 2009, the Australian garden nursery and garden maintenance industries alone accounted for a turnover of AUD 3.8 billion…. The increased economic importance of garden consumption has been accompanied by increased investment in tree-related advertising and significant growth in gardening content in popular media…. This market activity explicitly seeks to … promote novelty and changing fashion as mechanisms of sustaining the consumption of tree ‘products’ in the face of the longevity of many trees (Pearce et al. 2013, p. 78).

Or, put another way:

… turnover of trees in the private urban forest is firmly linked to processes of capital accumulation, in everything from the selling of tree products and services to the buying and selling of urban real estate itself (Kirkpatrick et al. 2013, p. 174).

As each house is sold and bought, the process repeats, as new owners plant and remove trees, ‘mark out [their] own territory’ (Head & Muir 2005, p. 91) and create their own personal space.

The future is small

Tree cover in Australian cities has increased over the past 50 years. Since most residents like trees, it seems unlikely that cover will decline rapidly in the near future; except of course where gardens shrink as properties are sub-divided and buildings expand.

Compared to many rural areas, the big problem in cities isn’t a shortage of trees, it’s a shortage of big trees and old trees. We value big old trees but – you know the acronym – N.I.M.B.Y.

A beautiful old tree in the city of Brisbane. Source: Brisbane Architecture Blog

This creates two challenges: how to save big old trees and how to grow big old trees. Most activity and legislation rightfully focuses on saving existing old trees. But, in the long term, this is a stop-gap measure. Like saving isolated trees in cropping paddocks. Many cities inherited big old trees from earlier times, before farms and large estates were sub-divided. Modern garden culture doesn’t create big old trees to the same extent.

Is there space in the city for big old trees? In parks and public spaces, most definitely, but not it seems in the frontal lobes or back yards of home gardeners. We must cling to the big trees we do have because we – and I mean we, not an abstract they – rarely intend to replace them.

Acknowledgements

Many thanks to Professor Jamie Kirkpatrick and Lilian Pearce for fact-checking this week’s post. This is the third in a series of posts on urban trees. The next post will look at trees and human well-being.

Further reading

Don't forget the repeat photo monitoring competition that's running all year.

Don’t forget the repeat photo monitoring competition that’s running all year.

Head, L. & Muir, P. (2005) Living with trees – perspectives from the suburbs. In Proceedings of the 6th National Conference of the Australian Forest History Society. (Eds M Calver and others). pp. 84-95. (Millpress: Rotterdam). [The full article can be downloaded for free from this link].

Kirkpatrick, J.B., Davison, A. & Daniels, G.D. (2012) Resident attitudes towards trees influence the planting and removal of different types of trees in eastern Australian cities. Landscape and Urban Planning 107(2), 147-158.

Kirkpatrick, J.B., Davison, A. & Daniels, G.D. (2013) Sinners, scapegoats or fashion victims? Understanding the deaths of trees in the green city. Geoforum 48, 165-176.

Pearce, L.M., Kirkpatrick, J.B. & Davison, A. (2013) Using size class distributions of species to deduce the compositional dynamics of the private urban forest. Arboriculture and Urban Forestry 39(2), 74-84.

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18 thoughts on “Why do we plant and remove urban trees?

  1. Fascinating. I’m in the middle of this juggle – we have three very big old trees on this suburban block, which we love, but they were planted on the fenceline where they bother multiple sets of neighbours, damage multiple sheds, *and* are right on top of the sewer line. I have planted several replacement trees in the middle of the block where they won’t need to be chopped for boundary reasons, and I’m trying not to whiten my knuckles waiting for them to hurry up and get tall enough to count as trees and not sticks. I’m hoping they grow to at least the start of a shady size before we have to give in to outside pressures and remove the other trees.

    • Hi Tiki, thanks for writing in. Your predicament seems to be the standard urban dilemma. It’s great to hear of some advanced planting taking place. Best wishes Ian

  2. Interesting that ‘old age’ is cited as one of the top reasons for removal. I would argue that most tree owners and managers do not have any appreciation or understanding of tree age and are often provided with poor advice from ‘professionals’. I think we are too quick to condemn trees to the chipper because their growth has slowed or is ‘blemished’ and they may not look like the ideal rendered landscape object that was intended. No doubt this reason is also linked to perceived risk factors and increased management costs but it would be interesting to see a deeper analysis of this motive. I love everything about old trees and it gives me great pain to see them removed from our urban forest due to some generic landscape aesthetic or risk averse management. Most of our urban trees don’t even reach maturity let alone live to become true veterans. The niche habitats provided by old trees are completely missing form our urban forests and this must have a great effect on urban biodiversity. We need to take every opportunity to learn more about their role and to preserve them where possible….and yes! more spaces for BIG trees please.

  3. Interesting stuff Ian, would love to do a similar study in the UK as a comparison (unless it’s been done and I’ve missed it!) I’m surprised that one of the top answers for planting trees wasn’t “for fruit”. A lot of apples, cherries, plums, etc. are planted by UK gardeners.

    • Hi Jeff, it would be fascinating to be able to compare garden styles across continents wouldn’t it. Many respondents did support planting trees for fruit – in fact 54% supported planting a tree for ‘fruit, nut or honey production’. Even so, the fact that nearly half of the respondents didn’t view this as a positive reason for planting a tree is surprising, and indicates how ornamental gardens are. It is possible that water limitations (especially during droughts) may constrain fruit production for many people too, but I am just speculating here. Thanks again for writing in, best wishes Ian

    • WOW! This is absolutely amazing. Everyone should have a look at this. The Seattle web link shows an interactive map with every city tree mapped with a clickable link that shows its species identity, size, annual environmental benefit and more, plus the estimated ‘yearly eco impact’ of selected trees for greenhouse gases, water, energy and air quality links. What a fantastic initiative. I wonder if any Australian cities are trying to build a similar system? Thanks very much for the link Justin. Best wishes Ian

  4. Urban heat island is a real issue, but south of Adelaide and Canberra, getting adequate winter sun and light is often a bigger concern for both amenity and energy use (the average Victorian house uses 80 times as much energy for heating as they do for cooling). Obviously deciduous trees make sense for this, but then they aren’t native. (Thanks for your very informative and entertaining writing, by the way)

    • Hi Ben, yes, great point. In the comments of my last blog Max Bourke provided a link to a recent review of Canberra’s urban forest (see this site). As well as the issue you raise, the report highlights that many residents were keen to reduce tree cover to maximize exposure of solar panels, which adds yet another issue. Perhaps the most general take home message from the University of Tasmania research was that peoples’ decisions were more likely to be based on aesthetics than functional issues. Perhaps this highlights that, if we want to sell functionality, we may have the best success if we can ‘sell’ function through aesthetics? Thanks for commenting, best wishes Ian

  5. Hi all, if you’re interested in learning more about what is happening with urban trees in Melbourne, the City of Melbourne provides some great material via this website: https://www.melbourne.vic.gov.au/sustainability/urbanforest/pages/urbanforest.aspx
    Also, significant or exceptional tree registers are becoming more common and can be a useful tool to protect trees that span cadastral boundaries (above and below ground!) in the relevant planning schemes. Perhaps you might like to check whether your local council has one and if not, perhaps give them some encouragement. Many thanks for this blog and all others Ian.
    Cheers, Lil.

  6. Pingback: Why do we plant and remove urban trees? | Urban Environment News

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