Climate-adapted, traditional or cottage-garden planting? How acceptable is ‘climate ready’ planting to the public, and what drives these reactions?

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By Helen Hoyle…..

The UN COP 26 2021 Climate Conference heightened public awareness of the need to act now to mitigate the climate crisis. This in turn precipitates a call to ‘futureproof’ cities by introducing resilient urban green infrastructure compatible with future climates. Yet how do the public respond to ‘climate-ready’ planting in public places, when this may be unfamiliar and very different aesthetically to native vegetation? My earlier research indicated strong public support for the introduction of aesthetically exotic, climate-adapted planting in public parks and gardens, particularly if it was better adapted to the changing climate than traditionally-used species, yet understanding of the values underlying this acceptance, and the socio-cultural drivers of people’s perceptions, was lacking. Matthew Pottage, the Curator of RHS Wisley, was also keen to know more about public attitudes to climate-adapted planting, having recently (2017) introduced an Exotic Garden at Wisley. Incorporating species such as dramatic cannas with large vibrant orange flowers, and Chinese dwarf bananas, this is an innovative experiment to gauge the response of exotic planting to the UK climate.

Our research at Wisley involved a comparative study of public reactions to three contrasting garden styles: the exotic, an informal, English cottage-garden style, with a wilder aesthetic, incorporating familiar native species such as foxgloves, geraniums and roses, and a traditional, English formal style of planting in blocks, incorporating plant species both native and non-native to the UK such as the dahlia, rose, and clematis.

The three contrasting garden styles at RHS Wisley, Surrey

We asked:

  • What is the key driver of people’s perceptions in relation to aesthetics, self-reported restorative effect, and plant and invertebrate biodiversity: planting style or socio-cultural variability?
  • What are the socio-cultural drivers of people’s held values in relation to climate change, the introduction of non-native species, and nature-connectedness?
  • Do the perceptions and values of people with a personal interest or professional involvement in landscape, horticulture or the environment diverge from those of other members of the public?

The research was conducted on-site at RHS Wisley, Surrey, UK. Members of the public were invited to walk through one specific area of planting. We wanted people to report their own responses to engaging directly with the planting, because “the environment is experienced rather than simply looked at” (Ittleson, 1973). The questionnaire addressed participants’ perceptions of the aesthetics, biodiversity and how mentally restorative it was to walk through the planting, participants’ beliefs and values including climate-change awareness and nature-connectedness, and participants’ socio-demographic characteristics.

The Exotic Garden, most preferred aesthetically, incorporates dramatic cannas with large vibrant orange flowers, and Chinese dwarf bananas,

Our findings revealed that:

  • Aesthetically, the exotic climate-adapted planting was preferred over other two styles, whereas the cottage-garden style was perceived as the least attractive to walk through, significantly less so than other two styles
  • In contrast, the cottage-garden style was found to be the most mentally restorative to walk through
  • Members of the public accurately perceived lower levels of native biodiversity perceived in the exotic climate-adapted garden-style
  • There was a direct relationship between climate change awareness and participants’ educational qualifications. Those with no formal qualifications had significantly lower awareness of the implications of climate change than other participants.
Although perceived as the least attractive garden, the Cottage Garden was the most mentally restorative to walk through

We also found that:

  • Participants who were professionally involved landscape, horticulture or the environment perceived lower aesthetic value, restorative effect, and native biodiversity for the planting overall than non-professionals
  • Those with a personal interest enjoyed the aesthetics of nature more intensely and had stronger climate change concerns than other participants.

Our findings inform policy and practice towards the realisation of environmentally and socially sustainable urban green infrastructure in public parks, gardens and greenspaces. That participants expressed a significantly higher aesthetic preference for the Exotic, (climate-adapted) Garden over the other two garden styles provides further evidence of public support for this unfamiliar style of planting, a positive transferable finding informing policymakers and land-managers seeking to ‘futureproof’ cities by introducing climate-adapted UGI in parks and gardens. Nevertheless, the cottage-garden style, perceived as the least attractive, was considered the most mentally restorative to walk through. This provides further evidence that different stimuli elicit contrasting responses in the public. Landscape planners and designers should draw from these findings to inform practice on the ground, also providing opportunities for restoration amongst familiar, naturalistic planting in public parks. When planning and designing culturally acceptable urban green infrastructure, professionals should also be mindful of the divergence of their own perceptions and preferences from those of the wider public. That we identified significantly lower levels of climate change awareness amongst people with no formal qualifications is a striking finding. It highlights a need to consider novel science-communication strategies to transcend formal educational channels if the public is to be better informed about the challenges of climate change and their implications for urban green infrastructure. This will also broaden understanding of the positive potential for climate-adapted urban green infrastructure to deliver ‘futureproofing’ benefits for climate-change mitigation and human mental wellbeing.

You can read the full open access paper here.

Thank you to Matthew Pottage for the opportunity to conduct this research at RHS Wisley.

Are Bristol’s plans to double tree canopy cover by 2045 feasible?

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by Danni Sinnett and Max Walters….

Trees provide many benefits to people and wildlife in urban environments. Seen as an opportunity to address climate and ecological emergencies, many cities are developing targets for increasing tree canopy cover and Bristol is no exception. Bristol’s One City Plan includes a target to double tree canopy cover by 2045.

We investigated the feasibility of Bristol’s target and explored different planting scenarios for its achievement. We asked the following questions:

  • How many trees would need to be planted between 2018 and 2045 to achieve the Bristol One City Plan target to double canopy cover over this period?
  • How does the timing of planting, size of trees when planted and tree mortality affect canopy cover and leaf area index over this period?

In 2018, the Forest of Avon Trust and partners assessed the benefits provided by Bristol’s trees using the i-Tree Eco software. This estimated canopy cover at 11.9%, lower than the 18.6% from the One City Plan. We used i-Tree Forecast to project future urban forest growth under different tree planting scenarios over 27 years. Because iTree Forecast requires an existing i-Tree Eco assessment we needed to model canopy cover growth from 11.9% to 37.2% (i.e. more than doubling) over the 27-year period, which is therefore a more ambitious target.

Three tree stock sizes were used, selected to be representative of the typical diameters of commercial nursery stock:

  • Small: equivalent to feathered trees
  • Medium: equivalent to light standards
  • Large: equivalent to heavy standards.

We calculated the number of small, medium and large trees needed to achieve the target under the following scenarios:

  • An equal number of trees planted each year to reflect continuous investment in tree planting
  • Intermittent planting every 5 years to reflect large scale projects such as major housing developments that might deliver significant tree planting in bursts
  • Planting concentrated between 2018-2027 to test the effectiveness of planting trees in the near term and allowing them to mature
  • Planting concentrated between 2036-2045 to reflect, for example, shortages in funding that might necessitate more planting towards the end of the period.

These were compared against a scenario of no new planting over 27 years and planting 10,000 small, medium or large trees per year, representative of current planting levels. The impact of tree felling was not considered but two annual mortality rates were used: 0.5% chosen to represent the best-case scenario and 3% to represent typical mortality rates in urban areas.

Key findings

We estimated that:

  • Assuming a 0.5% annual mortality rate, planting no additional trees or planting 10,000 small, medium or large stock trees per year will not achieve the 37.2% canopy cover target but would achieve a doubling of canopy cover from a baseline of 11.9%.
  • Assuming a more realistic 3% annual mortality rate, planting no trees results in the canopy cover decreasing to 11.4%, whilst planting 10,000 trees each year results in an increased canopy cover of around 4%.
  • Late planting between 2036 and 2045 achieves the desired canopy cover but requires the greatest number of trees to be planted and provides between 12% and 75% less leaf area than the other scenarios, which means less air pollution removal, carbon storage and sequestration.
  • Early planting between 2018 and 2027 achieves the greatest canopy cover for the smallest total number of trees, therefore requiring fewer planting locations. It also allows trees to mature providing the greatest benefits in terms of air pollutant removal, carbon storage and sequestration. However, it would require 35,000 heavy standards to be planted each year at 0.5% mortality increasing to 104,000 with 3% mortality.
  • Planting the same number of trees each year for 27 years requires more total trees but would result in a more stable population over time, ensuring that tree replacement strategies are more manageable. It would require between 18,000 and 44,000 heavy standards to be planted each year.

The greater the annual mortality rate, the more trees will need to be planted to achieve the canopy cover target. Given that Bristol’s current planting is around 10,000 trees per year, planting at least 35,000 trees per year is ambitious, especially given that higher mortality rates may require a greater number to be planted, increasing costs. Whereas adopting a continuous planting regime of 18,000 trees may be more feasible. This demonstrates the importance of good stewardship and long-term maintenance to allow urban trees to reach full maturity and provide the greatest benefits.

Trees along the Malago Greenway, Bedminster

Existing tree cover is not evenly distributed across the city, a study by Bristol City Council (2011) found that Greater Bedminster and Ashley, Easton and Lawrence Hill have the lowest levels of canopy cover in Bristol at 11% and 9% respectively. These neighbourhoods have also been identified to be some of the most deprived within the city. Although city wide targets are useful tree planting should be targeted to address inequalities across the city.

Summary of results for large tree stock equivalent to heavy standards

ApproachAnnual mortalityCanopy cover %Total number of treesSequestrated Carbon/tonTotal value of air pollutant uptake
No planting0.5%23.1469,545322,595.7£22,496,779
3%11.4240,384219,637.7£15,501,257
Current planting of 10,000 trees per year0.5%31.4723,186349,003.2£26,933,674
3%17.4433,596240,316.8£18,948,113
Continuous planting0.5%37.9927,384370,216.6£30,499,555
3%37.41,089,482310,457.8£30,642,603
Intermittent planting0.5%37.3898,114370,082.8£30,570,412
3%37.31,082,534314,760.9£31,520,209
Early planting 2018-20270.5%37.3787,282384,941.7£33,201,379
3%37.3821,568357,659.7£38,942,266
Late planting 2036-2045s0.5%37.31,154,472339,476.5£25,244,798
3%37.31,511,676251,159.4£20,664,378

You can read the full open access paper here: https://www.sciencedirect.com/science/article/pii/S161886672100323X.

Sharing a vision for high quality green infrastructure..

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By Helen Hoyle….

Organised by our own Hannah Hickman and Sarah O’Driscoll (Bristol City Council), the inaugural joint Bristol City Council – UWE Centre for Sustainable Planning and Environments (SPE) Symposium on Green and Blue Infrastructure took place at Bristol City Council’s Cash Hall on Monday 11th February. This provided an excellent opportunity for planners and researchers to come together to share policy and practice experience relating to the delivery of high-quality green infrastructure (GI).

First up was Bristol City Council’s Richard Goldthorpe, from the City Design Team. Richard focused on “Policy towards delivery” and highlighted some of the gaps and new developments in place-shaping policy. Richard introduced the need for a West of England Green Infrastructure Plan to bridge between the West of England Joint Spatial Plan (JSP) and the Bristol Local Plan. The JSP will set out a prospectus for sustainable growth to help the combined authority meet its housing and transport needs for the next 20 years, to 2036. He also emphasised the need for the Local Plan to link to the provision and design of specific parks and green spaces. Richard closed by emphasising the need for good research data to inform GI policy and delivery.

Richard Goldthorpe (BCC) presenting on “Policy towards delivery”

Next on the floor were Liz Kinsey (South Gloucestershire Council) and Kathy Derrick (Bristol City Council) who introduced “The Frome Reconnected” a collaborative project focusing on future-proofing the river Frome, involving Wessex Water, the Environment Agency, South Gloucestershire Council and Bristol City Council. They described the specific challenges facing the Frome and its catchment: urbanisation and an increase in impermeable surfaces increasing flood risk; diffuse pollution; heavily modified sections involving culverts and restrictive fish barriers and fragmented habitats. Possible positive strategies to address these challenges included river restoration to facilitate fish passage, with an increasing focus on health, recreation and the possibility of introducing green prescribing activities on the Frome.

Introducing “The Frome Reconnected”

Our own Associate Professor Danni Sinnett was the next to present the framework that underpins the RTPI award-winning “Building with Nature: a national benchmark for green infrastructure”. https://www.buildingwithnature.org.uk/. This was developed through a Knowledge Transfer Partnership with Gloucestershire Wildlife Trust funded by Innovate UK and the Natural Environment Research Council. Danni explained how developers’ and policymakers’ lack of understanding of the characteristics of high-quality GI had driven the development of the benchmark. She went forward to explain how the framework can be used to deliver high quality GI, setting out the core principles, (distinguishing a GI approach from a more conventional green space approach), and those focused on achieving benefits for health and well-being, water management and nature conservation. Danni highlighted specific case study projects including Elderberry Walk, awarded a Building with Nature Design Award for the entire Masterplan for 161 new homes on a brownfield site in Bristol, and Gloucester Services on the M5 motorway. The services (both N and S-bound) incorporate an outdoor picnic area, play facilities and habitat provision.

Danni Sinnett presents the framework underpinning “Building with Nature” the national benchmark for green infrastructure

The final presentation by Dr Helen Hoyle (SPE) focused on co-producing urban meadows in green spaces with local authority land-managers in Bedfordshire. This was part of a larger Natural Environment Research Council-funded research project, Urban BESS http://bess-urban.group.shef.ac.uk/ (Biodiversity and Ecosystem Service Sustainability). Researchers from the University of Sheffield and Cranfield University introduced native perennial meadows of different floral content and heights to areas of amenity mown grassland in contrasting urban contexts in Luton and Bedford. This was done to gauge public reaction and invertebrate response to increasing biodiversity on the sites. Helen worked in the bridging role between researchers and practitioners on the ground and reported on research focusing on the land-manager perceptions of the challenges and opportunities of making such changes. https://www.sciencedirect.com/science/article/pii/S1618866716305489 Findings highlighted the key factors as: Economic resources; Aesthetics, or the appearance of the meadows, and specific Locational context. Land-managers were aware that introducing floral meadows could make some areas of green space much more attractive for the public. Nevertheless, disposing of meadow cuttings at the end of the growing season was expensive, currently ruling out the possibility of introducing meadows as a cheaper management approach than mown grass. They were also aware that although many people now accept messier urban planting, there were still those who prioritised tidiness directly outside the front of their homes.

Helen Hoyle highlights land manager perspectives on introducing urban meadows

Watch this space for news on the next joint Bristol City Council – UWE Centre for Sustainable Planning and Environments Symposium.

Delivering high quality green infrastructure

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By Danni Sinnett

Globally, more people now live in towns and cities than live in the countryside. With urbanisation projected to increase into the future, and pressure on land for housing, we need to find a way of creating healthy places where both people and nature can thrive. This can be achieved by incorporating high quality green infrastructure into new and existing places.

Providing trees in each front garden in Edinburgh provides benefits as soon as people move in

Green infrastructure is a relatively new term that has gained traction in planning over the last 15 years or so, and differs from previous approaches in that the emphasis is on the creation of a coherent network of green and blue features that provide multiple functions, instead of focusing on individual spaces. These components are varied and include, for example greenspaces, parks and playing fields, street trees and landscaping, allotments, private gardens, wetlands, streams and other water bodies, as well as green roofs and walls. A critical function of this network is to provide connectivity within the urban environment and between the urban and rural.

Barking Riverside includes a network of high quality green infrastructure providing benefits for people and nature

There is now a wealth of evidence of the benefits, or so called ecosystem services, that green infrastructure can provide. For example, it can improve health and wellbeing by providing spaces for play, exercise, rest and relaxation, enhance the quality of development, and reduce air and noise pollution. It can also increase our resilience to the consequences of climate change by reducing flood risk and the effects of the urban heat island. Many of these can also save money, including through protecting communities from flooding, reducing ill health and improving quality of life. Ultimately, green infrastructure brings nature into the city, overcoming the ‘extinction of experience’ where increased urbanisation coupled with a reduction in time spent outdoors has decreased our contact with nature.

New development in Bristol combining a high quality walking environment with sustainable drainage

Despite all the evidence for green infrastructure and its apparent importance in our quality of life there are significant challenges in its delivery and management. Our research has been examining some of the reasons for this and has found that those working in the planning, design and creation of green infrastructure are struggling. For example, many are still unsure of what green infrastructure is, or should be, due to a combination of a shortfall in resources, knowledge or skills (Sinnett et al., 2017; Calvert et al., in press). In addition, developments often regarded as sustainable do not provide high quality green infrastructure. When we reviewed some of the systems that are used by developers to assess the sustainability of new places and buildings, we found that although many do include some measures of the quality of green features like parks and green roofs they rarely consider these features as a coherent multifunctional network (Calvert et al., in press). This can lead to missed opportunities to protect or enhance the existing green infrastructure or create features as part of new development.

High quality green spaces in the regeneration of a social housing estate in Lyon provide opportunities for rest and relaxation

A significant challenge is the current uncertainty over funding for long-term maintenance and management, with many local authorities unable to commit to this once construction has finished and people have moved in. This means there can be a tension between new developments being expected to provide green infrastructure, it being a desirable feature for potential residents, but the funding to manage the assets being precarious or uncertain, particularly over the timescale that vegetation takes to mature.

 

We have used these findings to develop a framework for high quality green infrastructure through a collaborative project with Gloucestershire Wildlife Trust. The framework consists of a set of principles informed by the literature, a review of existing standards for assessing the quality of green infrastructure, and consultation with stakeholders. The framework aims to overcome some of the challenges outlined above, addressing characteristics such as the creation of a network, local relevance and providing for the long-term management, as well as those aimed to deliver benefits for health and well-being, water management and nature conservation. This framework underpins Building with Nature, a new benchmark for green infrastructure (www.buildingwithnature.org.uk). This benchmark has been tested on a suite of planning applications and policies, and initial results are extremely positive. The framework is effective at ensuring a green infrastructure-led approach to new development, clarifying the expectations for green infrastructure early on the development process, and providing a starting point for conversations between stakeholders.

We hope to see this approach used to improve the quality of green infrastructure across our towns and cities so that people and nature can flourish.

Sinnett, D., Jerome, G., Burgess, S., Smith, N., Mortlock, R. (2017) Building with Nature – a new benchmark for green infrastructure. Town and Country Planning 86(10): 427-431. Available from: http://eprints.uwe.ac.uk/33406

Calvert, T., Sinnett, D., Smith, N., Jerome, G., Burgess, S., King, L. (in press) Setting the Standard for Green Infrastructure: the need for, and features of, a benchmark in England. Planning Practice & Research. Available from: http://eprints.uwe.ac.uk/38013/