Urban Greening - University of Sussex - Is Urban Greening the Future of Food?
Is urban agriculture the future of food security in the UK?
Dr Beth Nicholls is from the University of Sussex
and here she argues that City allotments could be as productive as conventional farms if done in right way.
If you live in a city or urban area, how far do you need to travel to access affordable fruit and veg? Can you buy fresh food within walking distance of your home or via a reliable public transport route? For the 1.2 million UK residents currently living in a ‘food desert’, who regularly have no choice but to shop in more expensive small convenience stores that stock limited fresh food, or dedicate a portion of their already limited food budget to public transport, the answer is no1. Given that around the world an increasing number of people are moving away from rural areas where food is traditionally grown, with 68% of people projected to be living in urban areas by 2050 (UN Department of Social and Economic Affairs) this raises the question of whether nutritious food would be more accessible, and could be produced more sustainably if more food was grown in and around urban areas?
Globally it is estimated that 6% of all farmland is urban, and some researchers have estimated that urban farming may already provide as much as
one fifth of the world’s food. However, because it is much less well regulated and monitored compared to more traditional farming methods, particularly in developing countries, estimating the potential for urban areas to produce food is difficult. Urban farms are often very small and ad hoc, and farmers may not always have permission to farm the land, making gathering data on this type of farming a challenge for researchers like me. However, in 2017 myself and a
team of researchers based at the University of Sussex decided to harness the power of ‘citizen science’ collaborating with growers themselves and training them how to collect data from their allotments and gardens to help us estimate the productivity of urban farming in the UK.
Thirty growers from Brighton & Hove took part in the study2 between 2017 and 2019, and regularly weighed their fruit and veg harvests to help us to estimate crop yields and the productivity of urban farming. They also recorded the insects visiting their flowering crops to help us estimate the importance of pollinators such as bees and hoverflies for urban growing, as well as keeping a record of any pests they encountered on their crops and what they did to tackle them, to quantify the risks to the environment from pesticide use in urban areas. In the Spring each year we held events at allotments and community gardens across the city to train growers in data collection methods, and all of the data was collected in personal ‘Grow Your Own’ diary which were later submitted to us online or by post. If you grow your own food and would like to have a go at collecting similar data from your garden, allotment or community growing space, you can access all the resources you need via the Team PollinATE website.
The data collected by the growers showed that urban farming can be very productive, with growers producing 70 kg of food per season on average, with some producing up to 260 kg per season. Accounting for the space the growers had, this equates to an average yield of approximately 1kg/m2, with some growers producing as much as 10 kg/m2. This compares quite favourably with yields produced in more traditional farming, where oilseed rape typically yields 4 kg/m2 and wheat 10 kg/m2. It is also important to note that our growers were only asked to submit data for insect pollinated crops (e.g. berries, apples, pears, beans, pumpkins), so these values do not include root vegetables such as carrots or brassicas such as cauliflowers or cabbages. Therefore, these values are actually likely to be an underestimation of the potential yield. Since our study was conducted, there has been a handful of additional studies of urban agriculture published that used similar citizen science methods. They also found urban farming to be very productive with average yields of 1.8 kg/m2/year for Leicester-based allotments3 and 5.94 kg⋅m−2 for small-scale Australian farms4, nearly twice the productivity of commercial vegetable farms.
Another encouraging result from our study was that the use of pesticides was generally very low in our study, with growers using chemical sprays in <10% of pest cases, suggesting the risks to the environment from urban growing are low. The one exception to this was slug pellets, which were used in 40% cases, and even though most people used organic pellets, this could still have effects on wildlife further up the food chain such as hedgehogs and birds.
To provide an estimate of the economic value of food produced in urban areas, a PhD student in the research team, Dr Linda Birkin, developed the Garden Shop Calculator. This allowed us and the growers to calculate how much their harvests would have cost to buy in a supermarket, and also what proportion of that harvest was directly ‘owed’ to insect pollination. You can try the calculator for yourself and submit your own data to our ongoing study online here. On average growers harvested £550 worth of food per season, with some growers harvests worth up to £2000, and again this was just the food pollinated by insects. In terms of the ‘value’ that was provided by insect pollinators, nearly £400 worth of food was ‘owed’ to insect pollinators on average per grower across a season demonstrating the value and importance of insect biodiversity to urban farming.
One limitation of our study is that when calculating the value of crops harvested, we did not account for the labour associated with growing food in urban spaces. The typically small-scale nature of urban farms means that mechanisation of tasks is not possible, so urban growing is often very labour intensive. Therefore, to fully determine the potential for urban growing to contribute to UK food security, it would be necessary to balance all the likely costs (e.g. fuel, water, labour) and benefits (e.g. improved access to fresh food, reduced food miles).
Other studies that have attempted this have found urban growing to be fairly inefficient in terms of resource use4, meaning careful management is necessary to make sure this type of farming is truly sustainable. At present it seems unlikely that urban growing could completely replace conventional farming as an approach to feeding the UK population. However, our study and others demonstrate the potential of urban growing spaces and show just how much food can be produced in small parcels of land right in the centre of busy cities.
Aside from food production there are numerous other benefits associated with urban farming, including the mental health and wellbeing benefits associated with improved access to green space, time spent outdoors engaged in physical activity and an increased connection to nature5. For example, a study in the Netherlands found that allotment holders over the age of 60 are healthier than their neighbours without allotments6. Many allotments also foster a great sense of community among growers and can serve as both therapeutic and educational spaces. Nature itself benefits from urban growing, with a recent UK study led by Bristol University showing that allotments host the highest abundance and diversity of insect pollinators than any other urban greenspace7. Growing spaces can also mitigate against the effects of climate change, for example improving a city’s flood defences through better absorption of rainwater than impervious surfaces such as pavements and tarmac and reducing the urban heat island effect.
Space for growing food in UK cities is in high demand and interest in urban growing rose substantially during the Covid-19 lockdowns, as did food insecurity, with as many as one in ten people forced to use foodbanks during this time. In Brighton & Hove where our study was based there are currently over 6000 allotment holders, representing approximately 2% of the total population of the city, but a further 1000 people remain on the allotment waiting list, suggesting the need to expand the area available for growing food in the city to meet demand.
One in eight people in the UK do not have access to a garden (rising to one in five in London), so city planners and developers should be strongly encouraged to provide access to growing space for residents and to incorporate this into new developments. Urban growing works particularly well at a community level where both the labour and harvests (think large gluts of courgettes!) can be shared. The UK imports approximately £8 billion of fruit and vegetables each year, but our research and others shows that green spaces in cities, such as allotments and community gardens, could play a role in meeting that demand and improving food security for UK residents in urban areas. Pesticides were used very infrequently by participants in our study, suggesting that the risks to health and the environment are also lower in urban areas compared to conventional farming. In a world of increasing urbanisation producing food in and around cities has the potential to improve health and provide habitat for wildlife, creating more sustainable cities
Notes:
3Edmondson, J. L. et al. (2020) Feeding a city - Leicester as a case study of the importance of allotments for horticultural production in the UK. Science of the Total Environment 705, 135930 (2020).
4 McDougall, R et al. (2019). Small-scale urban agriculture results in high yields but requires judicious management of inputs to achieve sustainability. Proceedings of the National Academy of Sciences, 116(1), 129-134.
5Clatworthy, J. et al. (2013) Gardening as a mental health intervention: a review. Mental Health Review Journal 18:214–225
6Van den Berg, A. et al. (2010) Allotment gardening and health: a comparative survey among allotment gardeners and their neighbours without an allotment. Environmental Health 9:74
7Baldock, K. et al. (2019). A systems approach reveals urban pollinator hotspots and conservation opportunities. Nature Ecology & Evolution, 3(3), 363-373.
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