As populations become increasingly urbanised, the preservation of urban green space (UGS) becomes paramount. UGS is not just dedicated recreational space such as public parks, but other types of informal green space are important, for example, street trees and roof gardens. Despite the potential from cross-sectional evidence, we know little about how to design new, or improve or promote existing UGS for health, wellbeing, social and environmental benefits, or known influencing factors such as physical activity. To perform a meta-narrative review of the evidence regarding the health, wellbeing, social, environmental and equity effects, or known influencing factors of these outcomes, of UGS interventions. Eight electronic databases were searched ((Medline, PsycINFO, Web of Science (Science and Social Science Citation Indices), PADDI (Planning Architecture Design Database Ireland), Zetoc, Scopus, Greenfiles, SIGLE (System for Information on Grey Literature in Europe)), and reference lists of included studies and relevant reviews were hand searched for further relevant studies. Eligibility criteria included: (i) evaluation of an UGS intervention; and (ii) health, wellbeing, social or environmental outcome(s), or known influencing factors of these outcomes, measured. Interventions involving any age group were included. Interventions must have involved: (a) physical change to green space in an urban-context including improvements to existing UGS or development of new UGS, or (b) combination of physical change to UGS supplemented by a specific UGS awareness, marketing or promotion programme to encourage use of UGS. Following a meta-narrative approach, evidence was synthesised by main intervention approach, including: (i) park-based; (ii) greenways/trails; (iii) urban greening; (iv) large green built projects for environmental purposes. Outcomes such as economic (e.g. cost effectiveness and cost-benefit analyses), adverse effects and unintended consequences were also extracted. Evidence was synthesised following the RAMESES guidelines and publication standards, the PROGRESS-plus tool was used to explore equity impact, and risk of bias/study quality was assessed. The findings from the evidence review were presented at an expert panel representing various disciplines in a workshop and these discussions framed the findings of the review and provide recommendations that are relevant to policy, practice and research. Of the 6997 studies identified, 38 were included. There was strong evidence to support park-based (7/7 studies) and greenway/trail (3/3 studies) interventions employing a dual-approach (i.e. a physical change to the UGS and promotion/marketing programmes) particularly for park use and physical activity; strong evidence for the greening of vacant lots (4/4 studies) for health, wellbeing (e.g. reduction in stress) and social (e.g. reduction in crime, increased perceptions of safety) outcomes; strong evidence for the provision of urban street trees (3/4 studies) and green built interventions for storm water management (6/7 studies) for environmental outcomes (e.g. increased biodiversity, reduction in illegal dumping). Park-based or greenway/trail interventions that did not employ a dual-approach were largely ineffective (7/12 studies showed no significant intervention effect). Overall, the included studies have inherent biases owing to the largely non-randomized study designs employed. There was too little evidence to draw firm conclusions regarding the impact of UGS interventions on a range of equity indicators. LIMITATIONS; CONCLUSIONS AND IMPLICATIONS OF KEY FINDINGS: UGS has an important role to play in creating a culture of health and wellbeing. Results from this study provide supportive evidence regarding the use of certain UGS interventions for health, social and environmental benefits. These findings should be interpreted in light of the heterogeneous nature of the evidence base, including diverging methods, target populations, settings and outcomes. We could draw little conclusions regarding the equity impact of UGS interventions. However, the true potential of UGS has not been realised as studies have typically under-evaluated UGS interventions by not taking account of the multifunctional nature of UGS. The findings have implications for policymakers, practitioners and researchers. For example, for policymakers the trajectory of evidence is generally towards a positive association between UGS and health, wellbeing, social and environmental outcomes, but any intervention must ensure that negative consequences of gentrification and unequal access are minimised.

The role of vegetation in mitigating the effects of PM(10) pollution has been highlighted as one potential benefit of urban greenspace. An integrated modelling approach is presented which utilises air dispersion (ADMS-Urban) and particulate interception (UFORE) to predict the PM(10) concentrations both before and after greenspace establishment, using a 10 x 10 km area of East London Green Grid (ELGG) as a case study. The corresponding health benefits, in terms of premature mortality and respiratory hospital admissions, as a result of the reduced exposure of the local population are also modelled. PM(10) capture from the scenario comprising 75% grassland, 20% sycamore maple (Acer pseudoplatanus L.) and 5% Douglas fir (Pseudotsuga menziesii (Mirb.) Franco) was estimated to be 90.41 t yr(-1), equating to 0.009 t ha(-1) yr(-1) over the whole study area. The human health modelling estimated that 2 deaths and 2 hospital admissions would be averted per year.

Despite the growing problem of anxiety and depression amongst young people aged 14-24 years living in urban settings, reviews about the role of exposure to green and blue spaces or nature in preventing anxiety and depression tend to focus on children, adults or sometimes adolescents. This review aims to explore whether exposure to green and blue spaces reduces the risk of anxiety and depression among young people aged 14-24 years living in urban settings and provide a conceptual framework. The academic databases CINAHL plus, Global Health, MEDLINE, ProQuest: Dissertations and Theses, PsycINFO, Scopus and OpenGrey were searched for research published in English between January 2000 and June 2020. All study designs were eligible. All included studies were assessed for quality. Searches identified 9208 sources with 48 meeting the inclusion criteria for the review. Experimental studies provided evidence that walking or being in a green space improves mood and state anxiety immediately following the intervention. Non-randomised evaluations and observational studies suggest that social interaction, physical activity, and mindfulness mediate the relationship between exposure to green space and mental health. We propose that the absence of noise and restorative qualities of green spaces promotes mindfulness and interrupt rumination, which in turn reduce the risk of anxiety disorders and depression. This review and the resulting conceptual framework provide evidence to healthcare professionals about the value of contact with nature and green social prescribing. For policymakers, it provides evidence about the value of bringing the benefits of forests, vegetation and nature into cities, and ensuring that these spaces are accessible and safe for young people to use.

Current UK guidance suggests that a ‘rootable’ soil profile of at least 1.0 m depth should be sufficient to allow adequate rooting of the majority of tree species in a range of soil types and climatic conditions [Arboricultural Journal (1995) vol. 19, 19–27]. However, there is some uncertainty as to what constitutes a loosened soil profile in terms of penetration resistance. In this study the root development of Italian alder, Japanese larch, Corsican pine and birch was assessed after 5 years of tree growth. These data were compared to penetration resistance measured using both a cone penetrometer and a ‘lifting driving tool’ (dropping weight penetrometer). Tree root number and percentage were significantly reduced by increasing soil penetration resistance measured with both the cone penetrometer ( P  <   0.050) and the ‘lifting driving tool’ ( P  =   0.011 and 0.008 respectively). The vast majority of roots were recorded in soils with a penetration resistance of less than 3 MPa (90.7%) with a significant amount in the less than 2 MPa class (70.2%). Root development of Italian alder, Japanese larch and birch all showed a similar pattern, but Corsican pine appeared to be capable of rooting into more compact soils. The ‘lifting driving tool’ can be used as an alternative measure of soil penetration resistance. This equipment is more cost effective, easier to use and capable of measurements at a greater depth than the cone penetrometer. The majority of Japanese larch and birch roots (84.3%) were recorded in soils where it took less than 15 impacts to penetrate one 10 cm soil depth increment. The modelled data also suggest that a penetration resistance of 2 and 2.5 MPa relates to 10 and 15 impacts respectively.