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Private Gardens

In 2002, an estimated 27 million people in the UK owned gardens. Domestic gardens contribute about a quarter of the total urban area in typical cities in the UK, and contribute up to 86% of the total number of trees in a city. Especially small gardens are important, as they contribute the greatest proportion to the total area of gardens, and the accumulated number of structures such as ponds, nesting sites or compost heaps is significant at the city scale. This indicates the importance of gardens on a wider scale, not only for humans but also nature. Private gardens are mainly used for relaxation and recreation, with over a third of garden owners surveyed in 2011 naming these as main activities in the garden, with gardening, eating, drying laundry and socialising being other common activities. Over 80% of gardens are used for more than one of these activities. (4, 14)

Access

For those able to use them, they can provide increased physical fitness, connection to nature, improved relaxation and recovery from trauma, and similar benefits related to stress avoidance and cognitive function. Gardening in one’s own garden has been shown to provide greater satisfaction than gardening in community/shared gardens. Where visible, the increased green space may help reduce mental fatigue and so have a positive impact on crime rates in an area. Private Gardens may have an especially important effect on young children due to being more readily accessible for children and providing a safe area for play and exercise. Private Gardens can also be hugely important resources for the elderly, however there can be barriers from decreased physical ability and lack of support. (1, 2, 4, 6, 8, 13)

Air Quality

Especially in gardens with trees (at least certain types) air quality can be significantly improved. This is dependent on the type of vegetation used and where it is planted. Trees are especially positive if they are on the leeward side of a high pollution area (e.g. a busy road). They can not only benefit those owning the domestic garden but the area surrounding them – depending on their size and location. However, there is little direct evidence available and effects are certainly only on a small scale. (2)

Pluvial Flooding

Plants and trees intercept rain and slow runoff, contributing to an attenuation of the peak flow and volume reduction of runoff through increased infiltration.  However, heavy and prolonged rainfall, with potential additional runoff from adjacent areas, can lead to waterlogging of the soil. This depends on local characteristics such as soil type and can be exacerbated by compacting the soil, e.g. through heavy footfall or parking of vehicles. (2, 12, 13, 17)

Fluvial Flooding

Urbanisation and decreased permeability of surfaces has been shown to impact the magnitude of flooding by increasing the amount of runoff a river receives. Increasing permeability of an area by 30% could lead to as much as a doubling in the magnitude of 100 year return period floods. Protecting permeable areas is therefore a significant contribution to keeping flood risk as low as possible. (9)

Climate Regulation

a 10% increase in veg surfaces would help control summer temperature increase (predicted 4 degrees) due to climate change (modelling study in Manchester). Additionally, the soil can store carbon, especially if disturbance is minimised. An average of 2.5 kg m-2 of carbon is stored in domestic gardens with 83% in soil (to 600mm depth), 16% in trees and shrubs and only 0.6% on average in grass and herbaceous plants. (2, 13)

Habitat Provision

Especially for invertebrates and birds, even small domestic gardens can provide an important habitat, but also for some animals that used to be common in low-intensity farmland (e.g. hedgehogs, frogs, bumblebees).  They are likely to support a fairly generalist array of species, though the importance of this should not be underestimated. Gardens have been shown to harbour more plant species (a study found the entire garden flora across the UK to consist of 1056 species) than any other form of urban green space. Plant composition can be homogenous though and include many non-natives. Another important factor can be the size of gardens: the ability to provide biodiversity is often related to the area and connectivity. While gardens have the potential to provide very valuable habitats, the way they are managed influences the realisation thereof greatly. (2, 5, 7, 10, 11, 13, 15)

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Low Flows

Infiltration allows groundwater recharge. Grassed areas are able to nearly completely eliminate runoff. However, increased water use in summer may occur and increase pressure on mains water. (2)

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Water Quality

reducing runoff improves water quality as less pollutants are carried into surface water bodies, but also because biological processes in the soil break down pollutants. Bioretention (the breakdown of pollutants in structures consisting of porous soil, mulch and various plants) has been shown to have significant potential to reduce pollution in runoff. Especially metals can be nearly completely (>90%) removed, ammonium and phosphorous have been found to be reduced by 60-80%. Nitrate, however, can be increased through bioretention treatment. Private gardens, especially if they are managed traditionally, are likely to contribute to nitrogen and pesticide pollution and could so even have a negative impact. (2,3)

Aesthetics

Gardens, where they are visible, provide high aesthetic benefits for the neighbourhood. In a study in Sheffield published in 2000, more than 50% surveyed stated the fact that gardening created “a more beautiful environment” as a contribution gardens make to the urban environment. (4)

Cultural Activities

Gardening has been linked to increased sense of self-esteem, identity and ownership. They can lead to strong place attachment and provide a forum for interaction between family members. Gardens allow playful activities as well as growing food, gardening to shape a place after one’s own imagination or creative activities like painting or photography. Private gardens may, however, completely discourage wider social interaction by providing a clear barrier to the outside through hedges and walls – this is dependent on their layout and the way they are used. Contrarily, it has also been found that private gardens encourage social interaction between neighbours as contacts are made across the garden fence – a study published in 2000 found that 23% of garden users value the opportunity to meet neighbours when in the garden. (1, 6, 8, 16)

Property Values

It is widely accepted that gardens add value to a property. A survey by HomeSearch found that a garden added 20% in value compared to a house without a garden. (19)

Flood Damage

Flood Damage. * While a single garden will have no significant impact, case studies like the previously mentioned one in Leeds show that the loss of a proportion of gardens in an area can contribute significantly to increased damage from surface water flooding.

Connecting these fragmented habitats (e.g. through tree lined streets for birds) and managing them on a larger scale, e.g. as a group of gardens in an area, could be an interesting opportunity to maximise their habitat potential. Benefits from individual gardens to the wider public could also be maximised by strategically managing gardens on a larger scale than the individual plot.

Considering the Bigger Picture

The vegetated, permeable area provided by gardens is reduced each year due to development pressures, individual choices regarding the design of the garden and its maintenance and to provide space for private vehicles. In London, for example, an area of 2.5 Hyde Parks (2.5x142 ha) of vegetated garden land is lost each year (14), and in a case study area in Leeds, paved area in gardens increased by 13% over the course of 10 years (12). . While domestic gardens have significant positive benefits for their owners, they are not accessible to the wider public and do therefore not contribute to increasing public access to green space. Especially domestic back gardens may not even provide aesthetic benefits as they may be hidden behind house fronts or fences/walls. This has implications on the ability of gardens to provide benefits – on a local as well as a city-wide scale. Fragmented habitats can also be unable to support wildlife even though the conditions would be given.

 

How can we make the most of our gardens?

Manage gardens on a larger scale: this could allow habitat connectivity and optimise benefit provision for all.

Open up walls to make gardens visible and increase the attractiveness of the area.

Improve soil structure and include ponds to maximise infiltration and allow storage of water in designated areas.

Inform on the ways gardens can be used for exercise, education and play in different demographics.

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Reduce use of pesticides and fertilizer to prevent polluted runoff and use of mains water for irrigation.

Enhance gardens for wildlife by providing a wide variety of plants and structures.

Additional Benefits

 

 

Trade-offs and Potential Dis-services

(Mental) Health

Gardens and gardening provide benefits through the physical exercise that they can facilitate as well as through providing a ‘retreat’ from everyday life and enabling interaction with nature. Reduced mortality, lowered blood pressure and cholesterol levels, increased bone density have been linked to gardening, as well as a later onset of dementia. Regular physical exercise reduces risk of coronary heart disease. The low intensity, regular exercise that gardening provides can be very beneficial. Gardening helps reduce depression and anxiety, and encourages creativity and self-expression. Views of nature encourage faster recovery from illnesses and increase attention, alertness and improved moods. Especially landscapes with high natural resemblance provide restorative benefits. (1,2,4)

Economic /Energy savings

Sheltering vegetation could reduce energy costs for heating and cooling – on average 30% cooling energy savings have been found. These can be maximised by choosing vegetation with a high albedo to increase the reflection of light and with it heat. At the same time, this relates to soil water availability, as evaporation and transpiration are the main reasons for the cooling effect. Winter heating savings can also be gained if gardens are used to plant hedges to insulate from wind (while avoiding shading the house too much or directing wind tunnels towards the house), 17% have been suggested for houses in Scotland, although there is less literature. (2,17)

Habitat Provision

Introduction of invasive species can be a problem. Also, using pesticides can diminish the value of gardens as a habitat. Native plants should be preferred and management intensities should be kept at a reasonable level – introducing areas for wildlife, like wildflower strips or leaving piles of leaf litter and dead wood can increase the value as a habitat. Domestic cats can also present a threat to wildlife. (7, 11)

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Water Use

the need for irrigation can increase water use in a garden and so demand on mains water and energy. This can have negative impacts on low flows and carbon emissions, or if not done decrease the cooling potential and aesthetic value. Choosing the right plants is important. (2)

Food Provision

Trees can act as buffers against noise and placed strategically minimise the impact of highly used roads.

Climate Regulation

Management of gardens can lead to an increase in emissions. This can be due either to the products and services used (greenhouses, peat, plastics etc) or the activities carried out (lawn mowing…). This means it is important to be conscious of how to manage a garden for it to be environmentally sustainable. (2)

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Water Quality

Using fertilizers and pesticides can have negative impacts on the water quality of receiving waters. If possible, these should not be used or substituted by organic products to minimise impacts. Keeping a compost heap can provide fertilizer and reduce waste production. (3, 11)

  1. Bhatti, M. (2006) ‘“When I”m in the garden I can create my own paradise’: Homes and gardens in later life’, The Sociological Review, 54(2), pp. 318–341.
  2. Cameron, R., Blanusa, T., Taylor, J., Salisbury, A., Halstead, A., Henricot, B. and Thompson, K. (2012) The domestic garden: its contribution to urban green infrastructure. Urban Forestry and Urban Greening, 11 (2). pp. 129-137.

The review suggests that there are significant differences in both form and management of domestic gardens which radically influence the benefits. Nevertheless, gardens can play a strong role in improving the environmental impact of the domestic curtilage, e.g. by insulating houses against temperature extremes they can reduce domestic energy use. Gardens also improve localized air cooling, help mitigate flooding and provide a haven for wildlife. Less favourable aspects include contributions of gardens and gardening to greenhouse gas emissions, misuse of fertilizers and pesticides, and introduction of alien plant species. Due to the close proximity to the home and hence accessibility for many, possibly the greatest benefit of the domestic garden is on human health and well-being, but further work is required to define this clearly within the wider context of green infrastructure.

  1. Davis, A. P., Shokouhian, M., Sharma, H. and Minami, C. (2001) ‘Laboratory study of biological retention for urban stormwater management.’, Water environment research: a research publication of the Water Environment Federation, 73(1), pp. 5–14.
  2. Dunnett, N. and Qasim, M. (2000) ‘Perceived Benefits to Human Well-being of Urban Gardens’, HortTechnology, 10(1), pp. 40–45.

Private gardens occupy a significant proportion of the total surface area of a British city. For many people, the garden represents their only contact with nature and their chance to express themselves creatively. Yet relatively little research has been carried out on the role and value of such gardens to human well-being. We report in this paper on a major survey on the role of private, urban gardens in human well-being, conducted with a wide cross-section of randomly selected garden owners from the city of Sheffield, England, over the summer of 1995.

  1. Gaston, K. J., Warren, P. H., Thompson, K. and Smith, R. M. (2005) ‘Urban Domestic Gardens (IV): The Extent of the Resource and its Associated Features’, Biodiversity and Conservation, 14(14), pp. 3327–3349.
  2. Gigliotti, C. M. and Jarrott, S. E. (2010) ‘Effects of Horticulture Therapy on Engagement and Affect’, Canadian Journal on Aging / La Revue canadienne du vieillissement. Cambridge University Press, 24(04), p. 367.
  3. Goddard, M. A., Dougill, A. J. and Benton, T. G. (2010) ‘Scaling up from gardens: biodiversity conservation in urban environments.’, Trends in ecology & evolution, 25(2), pp. 90–8.

A scale-dependent tension is apparent in garden management, whereby the individual garden is much smaller than the unit of management needed to retain viable populations. To overcome this, here we suggest mechanisms for encouraging ‘wildlife-friendly’ management of collections of gardens across scales from the neighbourhood to the city.

  1. Gross, H. and Lane, N. (2007) ‘Landscapes of the lifespan: Exploring accounts of own gardens and gardening’, Journal of Environmental Psychology, 27(3), pp. 225–241.
  2. Hollis, G. E. (1975) ‘The effect of urbanization on floods of different recurrence interval’, Water Resources Research, 11(3), pp. 431–435.

Studies have shown that the urbanization of a catchment can drastically change the flood characteristics of a river. Published results are synthesized to show the general relationship between the increase in flood flows following urbanization and both the percentage of the basin paved and the flood recurrence interval. In general, (1) floods with a return period of a year or longer are not affected by a 5% paving of their catchment, (2) small floods may be increased by 10 times by urbanization, (3) floods with a return period of 100 yr may be doubled in size by a 30% paving of the basin, and (4) the effect of urbanization declines, in relative terms, as flood recurrence intervals increase.

  1. Loram, A., Thompson, K., Warren, P. H. and Gaston, K. J. (2008) ‘Urban domestic gardens (XII): The richness and composition of the flora in five UK cities’, Journal of Vegetation Science, 19(3), pp. 321–330.
  2. Loram, A., Warren, P., Thompson, K. and Gaston, K. (2011) ‘Urban domestic gardens: the effects of human interventions on garden composition.’, Environmental management, 48(4), pp. 808–24.
  3. Perry, T. and Nawaz, R. (2008) ‘An investigation into the extent and impacts of hard surfacing of domestic gardens in an area of Leeds, United Kingdom’, Landscape and Urban Planning, 86(1), pp. 1–13.
  4. Royal Horticultural Society (2011) Gardening matters: Urban gardens. London.
  5. Smith, C. (2010) London: Garden City? Investigating the changing anatomy of London’s private gardens, and the scale of their loss., Greenspace Information for Greater London. London.
  6. Smith, R. M., Warren, P. H., Thompson, K. and Gaston, K. J. (2005) ‘Urban domestic gardens (VI): environmental correlates of invertebrate species richness’, Biodiversity and Conservation, 15(8), pp. 2415–2438.
  7. Taylor, J. R. and Lovell, S. T. (2013) ‘Urban home food gardens in the Global North: research traditions and future directions’, Agriculture and Human Values, 31(2), pp. 285–305.
  8. Tompkins, E. L. and Eakin, H. (2012) ‘Managing private and public adaptation to climate change’, Global Environmental Change, 22(1), pp. 3–11.
  9. Royal Horticultural Society (2016) Waterlogging and Flooding.

www.rhs.org.uk/Advice/Profile?PID=235 (accessed on 04/05/16)

Advice on preventing and dealing with water logging

  1. This Is Money (2015): So the ‘Waitrose effect’ adds 12% to your home’s value – but what else will? Ten top factors that boost a property’s price…

http://www.thisismoney.co.uk/money/mortgageshome/article-3033530/Ten-factors-boost-property-s-price.html

(Accessed on 04/05/2016)