Environmental benefits and impacts of greenspace development

Summary

This research aims to identify and assess the benefits and impacts of greenspace establishment in the urban environment

Determining the benefits of woodland on air quality

Impact of particulates, oxidants and other pollutants

Particulates, oxidants and other pollutants are a serious problem in the industrial, urban and peri-urban areas of developed countries and countries in transition. For example, Mootgavhar & Hutchinson (2000) identified a correlation between hospital admissions from chronic respiratory diseases and the index of respirable particulates in the air of Seattle, USA. Furthermore, a recent World Health Organisation report suggested that more people are killed prematurely by the effects of pollutants than through car accidents (WHO, 1999).

How urban and peri-urban trees and greenspace can improve air quality

As a result of their large leaf area and the turbulent air movements created by trees, woods hedges and shelterbelts take up more pollution from the atmosphere than shorter vegetation or other land uses (Fowler et al., 1989, Beckett et al., 2000b). The ability of trees to take up particles has been characterised through measurement of deposition velocities and capture efficiencies in wind tunnels and through micro-meteorological measurement in the field with good comparability of data from different approaches (Freer-Smith et al., 2004). There is now sufficient understanding to produce an integrated model of how urban and peri-urban trees and greenspace can improve air quality.

Emission characteristics, atmospheric chemistry and local factors (site and climate) affect the way in which urban trees and greenspace influence air quality. It is necessary to consider all major urban pollutants in an integrated study since their interactions are complex. For example, urban trees take up ozone, ammonia and particles but also release biogenic volatile organics (VOCs). VOCs can contribute to the downwind production of secondary organic aerosols and ozone. Recent modelling of pollutant indicates that some tree species will have net beneficial effects while others may not, particularly under some extreme climatic conditions.

Building a model

We have been able to use established stomatal conductance values (gs) for open pasture, Scots pine, spruce and oak to model the effects of pasture/park grass and tree planting scenarios on ozone, sulphur dioxide and nitrogen dioxide removal from urban air in a Community Forest (Broadmeadow & Freer-Smith, 1996). Data are now available on the concentrations of particulates in the UK urban environment (NETCEN) and also on deposition velocities (Beckett et al., 2000b; Freer-Smith et al., 2004) for a significant number of tree species. We also monitor gaseous and wet deposited pollutants at a number of woodland sites (Level 2 data). Thus a model which considers gaseous air pollution, particulates, aerosols and wet deposited pollutants could be developed for the first time.

Once intercepted by leaf surfaces it is important to consider the ultimate fate and ecological impact of particulates. Particulates can form a reservoir for chemicals moving into the plants, herbivores can ingest particulate matter on leaves, particles can be washed off on to soil and road surfaces or be redispersed to the atmosphere.

The design of urban and peri-urban tree planting

The design of urban and peri-urban tree planting to improve the appearance of towns, provide shaded areas for relaxation and to lessen the adverse noise, pollution and wind-buffering from vehicles (urban screening) has been widely considered in Europe and the US. Such issues are of increasing concern in both developed and developing countries.

Work on pollutant uptake indicates that current designs of the urban environment and of specific developments might be significantly improved in the extent to which they remove pollutants from urban air. Quite subtle changes such as proximity of planting to school playgrounds, or the mix of deciduous and evergreen species, might have rather significant impacts on health and other benefits. The end users are thus planners, architects and those responsible for maintaining urban green space (town/city authorities, etc). There are also potential benefits in trapping spray drift and other aerosols through windbreak incorporation in agriculture, roadside and industrial sites.

Long term sequestration

For pollutants such as sulphur dioxide, nitric acid, ammonia and nitrous oxides trees and other vegetation offer the possibility of long term sequestration. Anthropogenically derived particles include a wide range of elements (lead, cadmium, nickel and chromium) and many organic species (e.g. poly-nuclear aromatic hydrocarbons – PAH and dioxins which are potential carcinogens) so that field measurements and analysis is likely to be required if budgets and fates are to be properly considered. This is particularly the case in the urban environment for which limited data are available, contrasting with the position for conventional woodland, where deposition of these pollutants is recorded at over 300 sites across Europe.

Impacts of climate change on pollutant linkages

Overall impacts

Although there is some uncertainty in predicting future impacts of climate change, global and national scientific evidence suggests that the UK will be subjected to warmer and wetter winters, hotter and drier summers, rising air temperatures, increased storminess and heavier rainfall. These factors will contribute to an increase in the risk of significant pollutant linkages forming. As a result sources of contamination which currently pose little risk to the environment are likely to become significant in the future.

Climate change may lead to a requirement for more robust adaptation strategies for the sustainable development of contaminated and brownfield sites.

Specific impacts

The impacts of climate change may include:

• Pollution control measures may be compromised; for example containment barriers may fail.
• Pollutant linkages may be strengthened, or brownfield sites may develop new significant pollutant linkages; for example through increased soil erosion.
• The rate of natural attenuation or bioremediation may change.
• The mobility and volatility of certain organic contaminants in the ground will be affected by higher ground temperatures.

These impacts will also be affected by the vegetation on the site, which in-turn will be subject to potential ecological adaptation as a result of climate change.

Monitoring urban greenspaces using Methuselah

What is Methuselah?

Methuselah is a strategy for monitoring the sustainability of urban greenspaces in the UK and to assess their effectiveness in delivering the benefits they are purported to.

Research Objectives

Methuselah aims to:

• Fully integrate monitoring and evaluation into the management framework for greenspace sites
• Assess the current level of monitoring and evaluation information held for an existing site, including any gaps in the knowledge base
• Assess how this data contributes to the delivery of site objectives
• Fill knowledge gaps using methods from a range of monitoring protocols
• Measure the wider impacts of greenspace presence and site management
• Relate the management outcomes to Government policies, targets and sustainability indicators
• Assess the effectiveness of greenspace provision at the local, regional and national scale by combining data from a number of sites
• Identify areas where further research is needed
• Provide practical, process-based monitoring, in support of management cycles

Publications

Doick, K. J. (2008). Methuselah. A monitoring and evaluation strategy for greenspace. Forest Research.

Morris, J. (2009). Monitoring and evaluating Quality of Life for the Public Spending Review 2007. Research Summary by Social and Economic Research Group, Forest Research.

Pediaditi, K., Doick, K.J. and Moffat, A.J. (2010). Monitoring and evaluation practice for brownfield regeneration to greenspace initiatives. A meta-evaluation of assessment and monitoring tools. Landscape and Urban Planning. 97 (1), 22-36.

Doick, K.J. (2010). Learning lessons in monitoring brownfield land regeneration to greenspace through logic modelling. In. Proceedings of ‘British Land Reclamation Society: Promoting sustainable land use. Eds: H. Fox and H Moore. Restoration and Recovery Conference 2010. (Glamorgan, Wales. 7th-9th September).

Doick, K.J., Sellers, G., Castan-Broto, V., Silverthorne, T. (2009). Understanding success in the context of brownfield greening projects: success criteria and acceptable standards for urban greenspaces. Urban Forestry and Urban Greening. 8 (3), 163-178.

Doick, K.J., Pediaditi, K., Moffat, A.J. and Hutchings, T.R. (2009). Defining the sustainability objectives of brownfield regeneration to greenspace. International Journal Management and Decision Making. 10 (3/4), 282-302.

O’Brien, L., Foot, K., and Doick, K.J. (2007). Evaluating the benefits of community greenspace creation on brownfield land. Quarterly Journal of Forestry. 101 (2), 145-151.

Contact

Kieron Doick

Further Information

Use of land degraded by former industrial and urban activity makes an increasingly important contribution to the expansion of woodland. Trees planted on such sites offer immense social benefits in addition to the possibility of economic activity on formerly unproductive land. This programme supports the related objectives of the English, Scottish and Welsh Forestry Strategies and across Great Britain generally.

Pollutants in the Urban Environment (PUrE) framework

Introduction

The Pollutants in the Urban Environment (PUrE) framework is designed to deal with real life scenarios. This project utilised models and data from the development of the Ecological Impact Assessment (EIA) framework to demonstrate that PUrE provides a robust modelling and decision framework for dealing with pollutants in urban areas.

Using particulate pollution as an example

Particulate matter contains a mixture of pollutants, but the effects have primarily been studied by size rather than by composition. Therefore, research on particles could be significantly improved by applying an updated and integrated approach.

For PUrE, the upper size of particles will be limited to those that can be readily transported via air dispersion or suspension in flowing water. This will involve a more thorough characterisation of the particles (e.g. chemical, physical, biological properties, etc.), mapping of sources and movements, and an integrated assessment of the associated human and ecological health effects/risks.

The Forest Research component will determine the composition and bioavailability of particulate contaminants and assess their associated risk to ecological health. There are two primary components:

• A quantification of the composition, transport and bioavailability of particulates in ecological receptors
• A validation of models to predict particulate interception by vegetation.

Quantification of particulates in ecological receptors

This will use indicator vegetation species planted along a particulate gradient. The species selected will include those common in urban greening.

The vegetation tissue compartments will be analysed for their metal content, both before and after washing, to assess the amount of particulate adhered to the tissue surface and that transported within the plant.

In addition, a range of primary plant consumers will be used to assess the food-chain transport of particulate pollution. These will be related to air sampling data collected from the study sites.

Validation of models

The use of vegetation to mitigate particulate pollution has been recognised for a number of years. Models have been developed to predict the potential dry deposition of particles to urban tree planting.

This component of the project will validate and, if necessary, refine these models using air sampling data from an urban greenspace in London.

The results of this work will test existing models and refine those being developed during the development of the EIA framework and will provide a dataset for inclusion in the databases supporting the software.

PUrE publications

Sinnett, D., Hutchings, T.R. and Hodson, M.E. (2010) Food-chain transfer of Zn from contaminated Urtica dioica and Acer pseudoplatanus to the aphids Microlophium carnosum and Drepanosiphum platanoidis Schrank. Environmental Pollution 158 (1) pp 267-271.

Peachey, C.J., Sinnett, D., Wilkinson, M., Morgan, G.W., Freer-Smith, P., and Hutchings, T.R. (2009) Deposition and solubility of airborne metals to four plant species grown at varying distances from two heavily trafficked roads in London. Environmental Pollution 157(8-9) pp 2291-2299.

Sinnett, D., Hodson, M. E. and Hutchings, T. R. Food-chain transfer of cadmium and zinc from contaminated Urtica dioica to Helix aspersa and Lumbricus terrestris. Environmental Toxicology and Chemistry 28 (8) pp 1756-1766.

Sinnett, D. and Hutchings, T. (2009) Ecological Impacts Assessment of Pollutants in the Urban Environment (PUrE EIA) Level 1 Development.

Sinnett, D., De Munck, C. and Brunt, A. (2009) Ecological Impacts Assessment of Pollutants in the Urban Environment (PUrE EIA) Level 2/3 Development.

Peachey, C., Sinnett, D., Wilkinson, M. and Freer-Smith, P. (2009) Demonstration of the PUrE Framework using mixtures of pollutants – Ecological Impacts Assessment

Peachey, C., Sinnett, D., Wilkinson, M., Hutchings, T.R. and Freer-Smith, P. 2008. Demonstration of the PUrE Framework using mixtures of pollutants – Ecological Impacts Assessment. Final Report.

Sinnett, D., Hutchings, T.R., Hodson, M.E. Application of Ecological Risk Assessment to community greenspace. Poster presented at the University of Reading School of Environmental and Human Sciences post graduate research conference, 3-4th May 2007.

Vardoulakis S., Cleall P.J., Sinnett D., Chen Q., Tiwary A., Li Y-C., De Munck C.S., Chalabi Z., Sharifi V., Gummeneni S., Hutchings T.R., Fletcher T., Leonardi G.I., Azapagic A., 2009. Assessment of health and ecological impact of policy on a legacy contamination case study. 21st ISEE Conference on Food, Environment and Global Health, 25th – 29th August 2009, University College Dublin, Ireland.

Cleall P.J., Jones M.J., Thomas H.R., Kapelan Z., Dorini G., Hutchings T., Sinnett D., Swithenbank J., Sharifi V., Fletcher T., Chalabi Z., Vardoulakis S., Tiwary A., Azapagic A., 2009. Development of a software based decision support platform for assessing the impacts of urban pollutants. 21st ISEE Conference on Food, Environment and Global Health, 25th – 29th August 2009, University College Dublin, Ireland.

Pettit C., Azapagic A., Tiwary A., Sinnett D., Hutchings T., Peachey C., DeMunck C., Chung W., Sharifi V., Swithenbank J., Chalabi Z., Fletcher T., Vardoulakis S., Grundy C., Leonardi G., Thomas H., Cleall P., Jones M., and Jefferis, S. More Sustainable Management of Pollution: Integrated Approach, Models and Tools. Paper presented at the SUE-MoT International Conference on Whole Life Urban Sustainability and its Assessment, 27 to 29 June 2007, Glasgow.

Sinnett, D. and Hutchings, T.R. 2007. Vegetation, pollution and human health case studies. Presented at the Sibthorpe Trust, Ecosystems and Health workshop, 4-5th July 2007, Liverpool.