A Great argument for gardens and against pavement

July 19th, 2013

Crazy paving?

by Chris Sherrington


It’s tidy and hard-wearing. You can park your car on it, getting it off the side of the road, and it doesn’t need watering or mowing. What’s not to like about block paving your front garden, if you’re lucky enough to have one?

It’s little wonder, then, that there is such a trend for front gardens to be paved over to make way for car parking. In 1991, just 16% of UK households with front plots had turned over 85% or more of the area to hardstanding. By 2011, 30% had done so – just under 7 million front gardens – calculated to be an area ‘equivalent to around 100 Hyde Parks’.

The Committee on Climate Change (CCC) Adaptation Sub-Committee notes this development with concern, reporting that in towns and cities the proportion of gardens that have been paved over expanded from 28% of total garden area in 2001 to 48% in 2011. But how do we evaluate the effect of this dramatic change in the urban landscape?


External space

The concept of negative externalities, where a polluter imposes an uncompensated cost on others, is one which is well understood in public discourse. A typical policy response in such cases is to impose a tax so that the ‘marginal private costs’, i.e. those faced by the polluter in question, ‘internalise’ the otherwise uncompensated costs. In theory the outcome of this should be a level of pollution that is socially optimal, in the sense that the tax deters unnecessary pollution, and the impact of the remainder can be mitigated through the tax received. The origins of the landfill tax lie in this approach.

Less well known is the concept of a positive externality. This is where an activity provides benefits for others, but those providing the benefit remain uncompensated. The classic example of this, as I remember well from my university environmental economics lectures, is vaccination. When people are vaccinated against a disease, the likelihood of those who are not vaccinated catching the disease is also reduced. It is the fact that the (perhaps unwitting) beneficiaries do not pay for this benefit that makes it an externality, albeit a positive one.

Perhaps positive externalities are less well known because they are less common. When pressed for a second example, I remember the lecturer offering ‘front gardens’ almost apologetically – the notion being that a beautiful front garden provides free benefits, primarily aesthetic, to passers-by and neighbours.  As an economist, a rational response might be to suggest that the householder provides a collection box on the wall to which passers-by can contribute. However, as a human being, I’d rather just enjoy my flourishing front garden and not worry about my unpaid generosity!


Concrete concerns

One of the key issues associated with paved gardens, which is of concern to CCC, is the greater risk of surface water flooding. The report mentioned above highlights that surface water flooding in urban areas is already on the rise as a result of paving over green spaces, and that it may increase further with more intense rainfall due to climate change.

As someone who lives at the bottom of a hill, I find this rather concerning. But while much of the attention is on the escalation of flood risk, there are other negative impacts, including loss of biodiversity and fragmentation of wildlife habitat, loss of aesthetic amenity, and localised heating effects. As well as being attractive, front gardens containing trees and large shrubs provide shade, and some of the rainwater that soaks into a garden will evaporate, causing a cooling effect around the house. This is lost if the garden is covered with hard impermeable surfaces and can cause local temperatures to rise (often referred to as the ‘urban heat island’ effect). With heatwaves likely to become more frequent, this is not an encouraging development.


Seaside garden

Not just a pretty place: the positive externalities of a green garden include both environmental and aesthetic benefits. Photo by *Susie*/sue/chasetheclouds, via Wikimedia Commons



Beyond these reasonably measurable impacts, front gardens play an important social role, acting as a liminal space between public street and private house. Working in a front garden presents opportunities for interactions with neighbours, which can assist in the development of stronger community relations. Without living things to tend, activities such as washing the car, or perhaps eradicating ‘weeds’, offer little reason to linger, leading to fewer chance interactions with neighbours.


Block paving?

It seems that the costs faced by the private householder in converting their own garden to hardstanding do not reflect the wider costs this choice imposes on society. Does this mean that there should be a tax on such activities? I’m not so sure this would be the best approach.  Focusing solely on flood risk, the nature of the impacts would vary considerably depending on location. Accordingly, a tax designed to internalise external costs, levied, for example, on each square metre converted to hardstanding, would have to be set at different levels across the country, reflecting the likely impacts in each drainage basin. The associated transaction costs would be excessive.

Another approach is to deal with these issues through the planning system. This is now being done – planning permission is required for any non-permeable paving of over 5m2 in area, and DCLG has issued guidance recommending the use of permeable surfaces. However such measures have only limited impact, and individual councils only have powers to request that residents do not pave front gardens. Relying on goodwill among citizens is unlikely to stop the rot when parking costs are ever increasing and time pressures make maintaining a front garden challenging for many.

Moreover, planning policies can be rather blunt and tend to focus on what cannot or must be done. They also take effect only when significant changes to a front garden are proposed. Even if fully implemented and enforced they may not necessarily stop the piecemeal reduction in urban greenery, and would provide no incentive for improvement.


A better path

Perhaps a better way to encourage ‘socially optimal’ management of front gardens would be to make payments for the benefits provided.  If it could be achieved in a simple way, giving green fingered people pounds in their pocket would certainly be an incentive. I recently attended a Landbridge workshop on ecosystem services which discussed how to incorporate the value of such services in decision making. Direct payments are one possible approach, and the government’s Ecosystems Markets Taskforce has identified the potential for Payments for Ecosystem Services (PES) to bring about environmental benefits in a cost efficient manner.

Much of the discussion on PES relates to large landowners, for obvious reasons – transaction costs are lower as a proportion of overall costs (and benefits). However, some problems are most keenly felt where more people live, flooding again being a good example, and this makes operating PES-style schemes in urban settings an attractive option.


Hull and high water

It appears that the approach can be successfully applied at the household level. A Defra-funded trial in Hull involved the local water company providing water butts, and disconnecting downpipes from the mains drainage with water instead dispersed onto the garden. This was shown to be a cost-effective method of reducing flood risk and reducing the contamination of water courses during heavy rain. For the water company, a preventative approach cost much less than would the downstream clean up. Applied, as it was, on a neighbourhood level, individual householders had the sense that they weren’t doing it on their own.

This approach was successful in an area which still had the 2007 floods in recent memory. Whilst not everywhere is as prone to flooding as Hull, for water companies there is always a cost to dealing with ever higher peak flows of surface water runoff, whatever the geography of the city. As a key beneficiary of measures that reduce flood risk, they may have the willingness to provide the financial foundation to develop such schemes across the UK. Such an approach might both protect existing front gardens and incentivise a move away from car-friendly concrete.

Who else might be willing to chip in? There are many other benefits of front gardens, but none so readily quantified as those relating to water. What is the value of a magnolia in full bloom in spring down the road, or the chance to show the butterflies to our children on the way to school?  Are there benefits to the NHS from improved mental health due to greener local environments? And does less concrete mean less crime? This perhaps is the greater challenge, to identify just how much we benefit from green gardens and compensate the gardeners of the UK accordingly.

If the carrot grown in Hull could be propagated elsewhere, there would be less need for poorly wielded sticks. And perhaps there would be many more happy gardeners who felt that their contribution to the neighbourhood and wider community was more fully recognised.


Chris Sherrington


Chris Sherrington


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