Greenspace is increasingly being recognised as playing an invaluable role in the mental health and well-being as well as the physical health of communities. This can be through:
- A place to take part in outdoor activities
- Safe green transport networks enabling people to walk or cycle
- Mitigating air pollution
- Providing shade.
Physical activity has many health benefits, reducing the risk of developing diabetes, coronary heart disease and some cancers, as well as improving recovery times after periods of ill health. There are also benefits for mental health. Improvements in the health of the population benefit society as a whole, by reducing the burden on the NHS and the number of days’ absence from work due to ill health.
Many people, particularly those living in urban and deprived communities, are often not able to engage in physical activity due to financial restraints, lack of facilities, or access to facilities. Urban greenspace can provide an easily accessible, safe and low-cost environment for physical activity. This may include anything from walking, cycling and socialising to organised sports events and conservation activities. The importance of providing greenspace to local communities that is in close proximity to residential areas has been recognised by a number of Government advisors, including Natural England.
Particulate pollution originates from a number of sources, including traffic and industry, and is known to cause respiratory problems in human populations. Over the past 15 years, concentrations of PM10 (particles with a diameter of less than 10 µm) have decreased significantly due to the move away from coal to natural gas in electricity generation, improvements in coal-fired power stations, and newer diesel engines capable of meeting tighter emission regulations. Despite this, many urban areas in the UK still exceed the air quality standards set to protect human health. The UK Air Quality Standards, based on PM10, are 50 µg/m3 as a 24-hour running mean (not to be exceeded more than 35 times in a calendar year), and an annual limit of 40 µg/m3.
Many studies demonstrate that trees and other vegetation can reduce particulate concentrations in the air. The particles are deposited and, to some extent, retained on the leaves and stems of plants. This can have significant health benefits for people living in the area.
The urban heat island effect means that urban areas are often significantly warmer than rural areas. Greenspace can help cool urban environments – vegetation has higher evaporation rates and does not absorb and store heat to the same degree as buildings and roads.
The incidence of skin cancer is increasing in the UK, particularly among young people. The Chartered Institute of Environmental Health has highlighted the role of trees in providing shade as one measure that can reduce skin cancer.
Greenspace should be designed to encourage and enable access for the wide range of visitors that can be expected in many of our urban areas. This may include:
- At the regional level – providing greenspace that is accessible without the need for a car, or by linking in with other greenspaces or paths to enable walking and cycling routes to be created
- At the local level – incorporating in greenspace design elements such as sports pitches, trim trails (series of gym equipment like parallel beams) or play areas
- Organised activities – for example local Walking for health groups – can provide an opportunity for socialising.
The ability of trees to intercept particulate pollution varies between species, throughout the age of the tree and with the planting design. Trees with dense foliage (e.g. conifers), sticky or hairy leaves (e.g. birch), and those in leaf all year round have been shown to have higher capturing efficiency. Trees also have greater potential to intercept particles if they are planted in strips across the prevailing wind direction, as opposed to in large blocks – the edge effect means that particulates held in the air are exposed to a larger surface area of planting block. Planting can also be targeted along sources of particulate pollution, for example by planting trees alongside roads, to increase the potential for air quality improvements.
The use of greenspace to improve the health of local populations needs to be balanced against other factors involved in their design. For example, species selection will play an important role in any biodiversity benefits, levels of pollen and emissions of volatile organic compounds, as well as the aesthetic appeal of the greenspace.
A study by Forest Research’s Urban Greening Research Group aimed to estimate the potential for a greenspace initiative to reduce levels of particulate matter (PM10) in an area of East London and the corresponding human health impacts in terms of mortality and morbidity. It also aimed to demonstrate how this type of integrated modelling approach, comprising both environmental and health models, can be used by practitioners wishing to target greenspace creation to areas where air quality is of concern.
The study used a 10km by 10km region covering two London boroughs. The greenspace occupied 547 ha (5.5% of the total study area). Sources of PM10 from the whole of Greater London were modelled using the ADMS-Urban pollution model (Cambridge Environmental Research Consultants, UK) to calculate hourly PM10 concentrations at 1.5 m height (human receptor level) for the 10,000-ha study area. A map of average PM10 concentrations was then produced. This used 2004 emissions and meteorological data, and was completed by University of Manchester.
A canopy PM10-uptake model based on the Urban Forest Effects Model (UFORE) (Nowak, 1994) was then used to estimate PM10 interception by the proposed greenspace under a number of planting scenarios. The best-case scenario for PM10 interception was then used to reproduce the PM10 concentration map for the area, for use in the human health modelling. Two models were used to estimate the mortality and hospital admissions, as a result of PM10 exposure, of the populations within the London Boroughs of Newham and Greenwich. This work was carried out by the London School of Hygiene and Tropical Medicine.
The results of the PM10 interception modelling demonstrated the importance of both the area of greenspace and the species choice. Douglas fir, due to its greater deposition velocities and leaf area index values, has a significantly greater capacity than sycamore to intercept particulates from the atmosphere; sycamore appears only slightly more effective than grass. This represents a fourfold increase when trees are included in urban greenspace design, equating to a removal rate of 0.12 t/ha/year.
The amount of PM10 interception is directly proportional to the area of greenspace. The PM10 reductions for the whole greenspace area are:
- 17.99 t/year (0.03 t/ha/year) under 100% grassland
- 60.49 t/year (0.11 t/ha/year) under 100% sycamore
- 1277.13 t/year (2.33 t/ha/year) under 100% Douglas fir.
The PM10 reductions within the whole study area (10,000 ha) are:
- 0.006 t/ha/year under 100% sycamore
- 0.128 t/ha/year under 100% Douglas fir.
The estimated health benefits based on implementation of the 100% Douglas fir scenario within the East London Green Grid study area suggest that two to three deaths and two to three hospital admissions are averted each year.
Nowak, D.J. (1994). Air pollution removal by Chicago's Urban Forest, in Chicago's Urban Forest Ecosystem: Results of the Chicago Urban Forest Climate Project. Radnor, PA, US Department of Agriculture, Forest Service, Northeastern Forest Experiment Station, USA.
The Urban Regeneration and Greenspace Partnership has extensive experience of species selection for air-quality improvements, and can provide research-based advice and guidance on the design of greenspace to encourage access.
Forest Research has a track record in conducting research on the impacts of vegetation and trees on urban air quality. Our extensive modelling capabilities enable estimation of the potential air quality benefits from different greenspace scenarios. Linking these to human health models, we can predict the reductions in mortality and morbidity that greenspace may bring.
Our social scientists have a versatile monitoring and evaluation toolkit to determine the role and success of urban greenspace in meeting its objectives in terms of access, visitor profiles and usage.
O’Brien, E. (2005). Trees and Woodlands – Nature's Health Service (PDF-2760K). Forest Research, Farnham.
O’Brien, E. and Snowdon, H. (2007). Health and well-being in woodlands: a case study of the Chopwell Wood Health Project (PDF-139K). Arboricultural Journal 30, 45–60.
O'Brien, E., Greenland, M. and Snowdon, H. (2006). Using woodlands and woodland grants to improve public health. Scottish Forestry 60, 18–24.