Maximising the environmental benefits of gardens through optimal planting choices and understanding of occupants' engagement

Background
Domestic gardens form 15-25% of total area of most UK towns and cities. Most of the UK population is urban (>80%) and has access to domestic gardens (>85%), so what we plant and how we manage our gardens can have a significant environmental impact. Recent research1,2 links certain garden plant characteristics (e.g. leaf hairiness or high evapotranspiration rate) with the capacity to provide ecosystem services including rainfall capture, localised cooling, or removal of airborne pollutants. Increased use of plants with specific environmental benefits in gardens would not only reduce environmental risks posed by extreme weather and pollution, but also increase sustainability of urban spaces.
We know that some garden plant species possess highly beneficial traits, but also that 'monocultures' of single species are undesirable. An evaluation of promising species' performance within a wider community structure is thus essential. Moreover, increasingly extreme and unpredictable weather conditions require a range of functions to be delivered by the same garden space. Unfortunately, a recent Royal Horticultural Society survey shows a decline in garden vegetative cover. Vegetation is lost to paving, with detrimental effects on the control of flooding, urban temperature and atmospheric pollution3. New evidence and clear advice to gardeners is needed to reverse the decline in ecosystem service provision by domestic gardens.
Approach
The student will study contrasting garden plant communities in controlled experimental conditions to describe the range of environmental benefits they provide. Plants will be grown as single species monocultures and as mixtures, and their ability to reduce air and soil temperatures, reduce rainwater run-off and remove particulate air pollutants will be investigated and compared to non-vegetated areas. Detailed work will focus on assessing how plant traits (canopy size/density, leaf shape and surface properties, root system type) determine performance and how they interact with planting combinations. Clearly, as all planting decisions in a domestic garden are taken by or at the behest of the owner, this project will research the attitude of homeowners/landlords towards investigated planting strategies. A key element of the study will be understanding how homeowners may be 'nudged' towards making decisions that support social and ecological benefits in their neighbourhood.
As an illustration, plant communities to be investigated could be 'Mediterranean style' plants with small or hirsute leaves or 'Bold style' plants with large, glabrous leaves. Single species monocultures, multiple species mixtures of the same type and a mixture of species of both types can be studied to understand their relative performance. We will characterise their environmental benefits, ease of establishment and management, and compare these to paved areas representative of non-vegetated gardens.
The project features close collaboration between academia and the Royal Horticultural society - UK's largest gardening charity. Thus, alongside scientific discovery, one of the main outcomes of the project will be advice to RHS membership on simple and practical solutions which would encourage homeowners to develop their garden space to maximise environmental gains.
1 Blanusa et al. 2019 (doi.org/10.1016/j.ufug.2019.126391); 2 Vaz Monteiro et al. 2017 (doi.org/10.1016/j.enbuild.2017.02.011); 3 Cameron and Blanusa 2016 (doi.org/10.1093/aob/mcw129)