Influence of evaporative cooling by urban forests on cooling demand in cities

Trees provide important ecosystem services to urban human society. Their absence can lead to more pronounced environmental and social consequences, for example the urban heat island effect. Evapotranspiration (Et) from trees reduces air temperature in the urban microclimate by converting sensible heat to latent heat. Quantification and valuation of the ecosystem services provided by urban trees is important for improving cost-benefit evaluations in support of protecting tree planting and maintenance budgets and, thus, for building climate change resilience into cities. Inclusion of Et cooling could improve ecosystem service valuation models by producing a more complete picture of the benefits that urban trees provide to society. This study explores two approaches for evaluating climate regulation as an ecosystem service of urban trees. Firstly, an enthalpy-based approach was adopted to valuate latent heat of evaporation from tree transpiration (in three case study urban forests) by equating it to an equivalent service from an active direct evaporative cooling system. Secondly, energy savings to air-conditioned buildings was modelled using TRNSYS and TRNFLOW simulation programs with and without air precooled and humidified by urban trees. Trees are shown to provide substantial urban cooling with an annual valuation of £84 m estimated using the enthalpy-based approach, or ranging from £2.1 m to £22 m using TRNSYS and TRNFLOW dynamic simulation programs; both for inner London case study. The latter savings arose from a modelled 1.28 – 13.4% reduction in air-conditioning unit energy consumption. Challenges around assumptions of homogeneity in both built form and urban forest canopy effects are discussed. The case study examples highlighted differences in Et cooling between tree species, with Castanea sativa, Prunus avium, Quercus petraea, Platanus hybrida and Fagus sylvatica typically providing more Et cooling than any of the other tree species commonly found in urban forests. The research highlighted a shortage of published Et data, particularly for urban environments

Interactive effects of composted green waste and earthworm activity on tree growth and reclaimed soil quality: a mesocosm experiment

On reclaimed landfill sites, the addition of organic matter such as composted green waste (CGW) to soil-forming materials can support tree survival and growth. CGW addition may also assist the establishment of sustainable earthworm populations, and in turn these organisms can promote further soil development through their burrowing and feeding activity. Despite such potentially mutual benefits, little research has been carried out into CGW and earthworm interactions with trees on reclaimed land. A twelve month, open field nursery experiment revealed the responses of the interactions between two tree species; Alnus cordata (Betulaceae) and Acer platanoides (Sapindaceae), CGW and the earthworms Aporrectodea longa (Lumbricidae) and Allolobophora chlorotica (Lumbricidae) in reclaimed soil. Controlled mesocosm conditions permitted a detailed investigation into the factors affecting tree growth and nutrient uptake, soil nutrient cycling and earthworm population dynamics. Results revealed that A. cordata growth was unaffected by CGW or earthworm addition. There was, however, a significant positive synergistic effect of earthworm activity and CGW addition on A. platanoides growth. CGW addition significantly increased levels of organic carbon and essential plant macro-nutrients in reclaimed soil while earthworm activity assisted decomposition of both leaf litter and CGW. Findings showed that CGW may serve as a suitable early source of organic matter to support earthworm population establishment on reclaimed sites. This experiment demonstrates that CGW improves reclaimed soil quality, thereafter supporting tree establishment and growth on reclaimed landfill

Effects of composted green waste on soil quality and tree growth on a reclaimed landfill site

The addition of composted green waste (CGW) into soil-forming materials during land reclamation can benefit tree growth by improvement of soil properties and provide an effective waste management solution. CGW addition may also assist the establishment of earthworm populations, which in turn aid soil development through their burrowing and feeding activities. An experiment was set up on a reclaimed landfill site, to measure the effects of CGW addition on soil physical and chemical quality and subsequently on the survival and growth of two tree species (Acer platanoides and Alnus cordata). A further objective was to measure the influence of earthworm (Aporrectodea longa) addition on the above. CGW addition led to significantly greater A. cordata growth (height and diameter) and increased survival rate. No benefits from CGW addition were observed on A. platanoides growth or survival, although this is likely due to soil drought conditions during establishment. CGW addition significantly increased levels of organic carbon and essential plant macro-nutrients in the reclaimed soil. Soil pH rose slightly across all treatments, with highest final pH under the control treatment. Earthworm inoculation, as used, was unsuccessful at increasing population density of A. longa. This experiment showed that CGW application can effectively improve tree establishment and soil quality on reclaimed landfill; however tree species selection is an important consideration, based on individual species tolerance and sensitivity to certain soil conditions. These findings will be informative to decisions on soil amendment and afforestation activities on similar reclaimed landfill sites

Valuing Wrexham's Urban Forest

Urban forests are a valuable source of ecosystem services in towns and cities. They help us alleviate problems associated with densely packed populations by improving local air quality, capturing carbon and reducing flooding. They also provide food and habitat for animals, such as birds and bees, and improve social cohesion in communities.However, the value of urban trees, both quantifiable and otherwise, is often overlooked within planning developments. By valuing the quantifiable services provided by trees in Wrexham County Borough, Wrexham County Borough Council and Natural Resources Wales can increase the profile of the County‟s urban forests, ensuring their value is maintained and improved upon. In addition, valuing these ecosystem services helps town planners, landscape architects and tree officers to plan where trees will be planted for the maximum benefit.A survey of Wrexham County Boroughs trees‟ to value a number of ecosystem services was undertaken in summer 2013 with the aid of i-Tree Eco, used for the first time in Wales. i-Tree Eco is a model developed by the US Forest Service that allows scientists to measure a range of ecosystem services provided by urban trees, from carbon sequestration to pollutant removal. The study was funded by Natural Resources Wales and Wrexham County Borough Council and was carried out by Forest Research. The quality of life for residents of Wrexham is significantly improved by its urban forest, helping alleviate flash flooding and sewer blockages, providing cleaner air and supporting wildlife such as pollinators. In addition, Wrexham‟s urban forest contributes significantly to the local economy, saving around £1.44 million in services per year. This would be enough money to plant nearly 800 medium sized oak trees in Wrexham and iscomparable to the amount needed to refurbish Wrexham cemetery (Wrexham.com, 2014). Wrexham has a high density of trees but low canopy cover compared to similar sized towns. A further 28% of Wrexham‟s urban space could be planted with trees, bringingWrexham in line with other urban areas. Wrexham‟s urban forest could also be improved by planting a higher diversity of tree species, improving its resilience to pests and diseases. The number of large trees in Wrexham is above average for the UK and, in particular,there are many impressive old oaks. However, there are fewer large trees than recommended for a future-proofed urban forest, suggesting some room for improvement. Increasing planting of large stature trees may future proof Wrexham‟s impressive stock of large growing trees. A summary of key results is presented on page 5

Using a Conceptual Site Model for Assessing the Sustainability of Brownfield Regeneration for a Soft Reuse:A Case Study of Port Sunlight River Park (U.K.)

Brownfield regeneration to soft reuse such as recreation and amenity has become increasingly common due to the demand for the potential environmental, social and economic benefits that it can deliver. This has led in turn to an increased demand for improved tools to support decision-making for this style of regeneration: tools which are simple to use, based on robust scientific principles and preferably which can ultimately link to quantitative or semi-quantitative cost-benefit analyses. This work presents an approach to assessing and comparing different scenarios for brownfield regeneration to soft reuse and other end-points. A “sustainability linkages” approach, based on sustainability assessment criteria produced by the UK Sustainable Remediation Forum (SuRF-UK), is developed and used in a refined qualitative sustainability assessment, and applied to develop a conceptual site model of sustainability, for a specific case study site (Port Sunlight River Park, U.K., a public leisure park established and maintained on a capped and managed former landfill site). Ranking, on an ex post basis, highlighted the clear sustainability advantages that the establishment of the Port Sunlight River Park has compared with a hypothetical non-development scenario. The conceptual site model provides a clearer basis for understanding cause and effect for benefits and disbenefits and a rationale for grouping individual effects based on their ease of valuation, providing a road map for cost-benefit assessments by (1) being able to match specific linkages to the most appropriate means of valuation, and (2) transparently connecting the sustainability assessment and cost benefit assessment processes.</p

Valuing the urban trees in Bridgend county borough

Urban forests provide a range of services, often termed ecosystem services, that help alleviate problems associated with urbanisation. Trees improve local air quality, capture carbon, reduce flooding and cool urban environments. They provide habitat for animals,and can improve social cohesion in communities. Ecosystem service provision is directly influenced by management actions that affect the overall structure of an urban forest.The first step to improve the management of an urban forest is to better understand its current structure, composition and distribution in order to obtain a baseline from which to set goals and to monitor progress. By measuring the structure of the urban forest (the tree species present, their size and condition), the benefits of the urban forest can be determined and the value of these benefits calculated and expressed in monetary terms.Valuing services provided by the urban trees in Bridgend County Borough (Bridgend CB) could allow Bridgend County Borough Council (Bridgend CBC) and Natural Resources Wales (NRW) to increase the profile of the urban forest thereby helping to ensure its value is maintained and improved upon. The Bridgend CB, as described in this study, is spread across 5 separate urban districts with a total area of 4,400 ha. In order to gain a better understanding of the urban trees in Bridgend CB and to value the services they provide, an i-Tree Eco survey was undertaken in the summer of 2014. i-Tree Eco is a model developed by the US Forest Service to measure a range of ecosystem services provided by urban trees. This study was funded by NRW and Bridgend CBC and the survey was carried out by Barton Trees. This report presents a baseline quantitative assessment of the air pollution removal, carbon storage and sequestration, rainfall interception and visual amenity of the urban forest of Bridgend CB, and is accompanied with detailed information on the forest’s structure and composition. Residents in Bridgend CB benefit significantly from the urban trees present, including the provision of ecosystem services worth £950,000 per year. This value, however, excludes many of the ecosystem services of trees that are mnot currently assessed by i-Tree Eco, including cooling local air temperatures and reducing noise pollution. Therefore, this value is a conservative estimate of the ecosystem services provided. This study captures a snapshot-in-time ‘picture’ of the urban forest. It does not consider how the urban forest has changed over time or the reasons for this. Decisions on how the structure and composition of Bridgend CB’s urban forest should change in the future or how to ensure that it is resilient to the effects of a changing climate are beyond the scope of this report, though this study goes a long way to providing the necessary baseline data required to inform such decision making

The canopy cover Webmap of the United Kingdom’s towns and cities

Urban trees and other green infrastructure are advocated as a cost-effective sustainable solution to ameliorate the socio-economic and environmental challenges of urbanisation. UK research has only recently started to quantify urban trees. Tree canopy cover percentage (TCC) is a useful indicator of tree presence. Its estimation can be reproducible, simple, fast, and cost-effective; it can also be evaluated through citizen science, improving people’s appreciation for urban trees and widening the data collection resource pool. This research summarises a citizen science assessment of the TCC of the UK’s 5,749 urban wards. Descriptive statistics are presented spanning local authority to country. The area-weighted mean (and standard error) of TCC across urban wards was 17.3 ± 0.1%. Nationally, the TCC were 11.8 ± 0.5%, 15.7 ± 0.5%, 17.5 ± 0.2%, and 18.1 ± 0.5%, for Northern Ireland, Scotland, England, and Wales, respectively. Results show that only 27.6% of urban wards had a TCC higher than 20%, previously suggested as a minimum target for UK towns. The findings highlight substantial geographical variance in TCC equity, as well as a negative correlation between TCC and deprivation. This information will be of value in urban forest strategy and management

Individual Tree Data Standard

It is estimated that 40 million trees in the UK have been surveyed and the data stored in local authority databases. Data for just 1.1 million of these trees are included in the UK’s and world’s largest open-access tree database, Treezilla (https://treezilla.org/). Tree surveys are carried out for different purposes and often to different specifications. Many tree data collection protocols and methods overlap in their recommendations but differences between them make it difficult or impossible to compare, combine, or reuse data. To address these problems in 2019 the COMMUNITREE project partners drafted a new data standard for surveys of individual trees. The steps taken to develop the data standard are described in detail here: https://www.forestresearch.gov.uk/research/quantification-and-valuation-of-benefits-provided-by-urban-trees/individual-tree-data-standard/ . Standardised tree data collection and recording will enable people to easily share their data so that a single dataset can be recycled for many purposes. The Individual Tree Data Standard is a partnership between Forest Research, The Open University, Treework Environmental Practice, Natural Apptitude and was funded by Innovate UK and the Geospatial Commission

Investigating tree foliar preference by the earthworms Aporrectodea longa and Allolobophora chlorotica in reclaimed and loam soil

Afforestation can improve the delivery of ecosystem services from reclaimed landfill sites. Tree health is a key determinant of ecosystem service delivery, and is directly impacted by soil quality; which is driven by biological processes in the soil, reliant on leaf litter inputs to function. Different tree species have different litter quality, affecting the degree to which they support biological processes in soils and the development of abundant and diverse soil faunal communities. In recognition of their key role in improving soil structure and fertility - key attributes of soil quality, earthworms have often been the subject of research as a part of land reclamation, and these organisms have displayed preferences for specific types of leaf litter. This work utilised a choice chamber design to measure the foliar material palatability of two tree species used in land restoration (Alnus cordata and Acer platanoides) as a food source for two common European earthworm species (Aporrectodea longa and Allolobophora chlorotica), and the effect of a reclaimed soil quality on earthworm growth, survival and feeding preferences. The research revealed that both earthworm species initially preferred the foliar material of A. cordata over A. platanoides, with the leaves of the latter requiring higher degradation to become palatable to earthworms. The consumption of fresh leaves showed these are a suitable food source for earthworms in choice chamber experiments, which historically have instead relied on senescent leaf litter. Finally, high survival rates of both A. longa and A. chlorotica in the reclaimed soil treatment, in addition to consumption of leaf material of two tree species now widely used on reclaimed landfill sites, demonstrated that these earthworm species are suitable candidates for inoculation to reclaimed land