O.P. Jindal Global University, Sonipat, Haryana, 131001, India.
Global Reporting Initiative (GRI), South Asia, C/O, BSI Group India, Mira Corporate Suites, Plot No. 1 & 2, Ishwar Nagar, Mathura Road, New Delhi, 110065, India.
Environ Monit Assess. 2022 Mar 1;194(3):235. doi: 10.1007/s10661-022-09808-w.
Most governmental initiatives in India, to leash down urban air pollution, have yielded little results till date, largely due to purely technocratic vision, which is shrouded by technological, economic, social, institutional, and political hardships. We present this reflective article on urban greenery, as a proposition to urban authorities (e.g., pollution regulators, environmental systems' managers, urban landscape planners, environmental policy makers), shift from purely technocratic way of thinking to thinking with nature, by strategic greening of urban spaces, for long-term air pollution prevention and control measures. To that end, we offer a meta-analysis of recent (post 2005) global literature using four-stage PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) approach. We open the narrative by briefing about main pollutant filtration mechanisms by trees, followed by cognitive aspects of species selection (e.g., deciduous vs. evergreen, air pollution tolerance index, environmental stressors). Till date, most Indian studies on urban greenery mostly but focused on physiological aspects of trees. Here, we draw attention of urban authorities to an equally compelling, but yet less explored, aspect: design criteria, with reference to two most common urban configurations, namely, street canyon and open road. With pictorial depictions, we enumerate various categories of street canyons and discuss aspect ratio (building height to street width) and various wind flow regimes (isolated roughness, wake interface, and skimming), that the urban authorities should be cognizant about to maximize pollutant removal efficiency. For open road, we discuss vegetation barriers, with special emphasis on canopy porosity/density functions. In the final sections, we reflect on a potential systems' thinking approach for on-ground implementation, comprising of revamping of urban forestry programs, research and development, community mobilization and stakeholder engagement, and strategic outreach. In addition, we emphasize on means to harness co-benefits of urban greenery, beyond mere pollutant removal, to garner support from urban residents' communities. Last but not the least, we also caution the urban authorities about the undesirable outcomes of urban greenery that will require more process-level research.
印度大多数控制城市空气污染的政府举措迄今收效甚微，主要原因是纯粹的技术官僚主义观点，这种观点受到技术、经济、社会、制度和政治困难的影响。我们提出了这篇关于城市绿化的反思性文章，作为对城市当局（例如污染监管机构、环境系统管理者、城市景观规划师、环境政策制定者）的建议，即通过战略性地绿化城市空间，从纯粹的技术官僚主义思维方式转向与自然一起思考，以实现长期的空气污染预防和控制措施。为此，我们使用四阶段 PRISMA（系统评价和荟萃分析的首选报告项目）方法对最近（2005 年后）的全球文献进行了荟萃分析。我们在叙述中简要介绍了树木主要污染物过滤机制，然后介绍了物种选择的认知方面（例如，落叶树与常绿树、空气污染耐受指数、环境胁迫）。迄今为止，印度大多数关于城市绿化的研究主要集中在树木的生理方面。在这里，我们提请城市当局注意一个同样引人注目的、但尚未得到充分探索的方面：设计标准，参考两种最常见的城市配置，即街道峡谷和开阔道路。我们通过图片说明列举了各种街道峡谷类型，并讨论了城市当局应该意识到的方面比例（建筑物高度与街道宽度之比）和各种风流模式（孤立粗糙度、尾流界面和滑行），以最大限度地提高污染物去除效率。对于开阔道路，我们讨论了植被屏障，特别强调了树冠孔隙度/密度函数。在最后几节中，我们反映了一种潜在的系统思维方法，用于地面实施，包括城市林业计划的改进、研究和开发、社区动员和利益相关者参与以及战略外联。此外，我们强调了利用城市绿化的共同效益的手段，超越单纯的污染物去除，以获得城市居民社区的支持。最后但同样重要的是，我们还提醒城市当局注意城市绿化可能带来的不良后果，这将需要更多的过程级研究。
