Urban heat mitigation by green and blue infrastructure: Drivers, effectiveness, and future needs.

The combination of urbanization and global warming leads to urban overheating and compounds the frequency and intensity of extreme heat events due to climate change. Yet, the risk of urban overheating can be mitigated by urban green-blue-grey infrastructure (GBGI), such as parks, wetlands, and engineered greening, which have the potential to effectively reduce summer air temperatures. Despite many reviews, the evidence bases on quantified GBGI cooling benefits remains partial and the practical recommendations for implementation are unclear. This systematic literature review synthesizes the evidence base for heat mitigation and related co-benefits, identifies knowledge gaps, and proposes recommendations for their implementation to maximize their benefits. After screening 27,486 papers, 202 were reviewed, based on 51 GBGI types categorized under 10 main divisions. Certain GBGI (green walls, parks, street trees) have been well researched for their urban cooling capabilities. However, several other GBGI have received negligible (zoological garden, golf course, estuary) or minimal (private garden, allotment) attention. The most efficient air cooling was observed in botanical gardens (5.0 ± 3.5°C), wetlands (4.9 ± 3.2°C), green walls (4.1 ± 4.2°C), street trees (3.8 ± 3.1°C), and vegetated balconies (3.8 ± 2.7°C). Under changing climate conditions (2070-2100) with consideration of RCP8.5, there is a shift in climate subtypes, either within the same climate zone (e.g., Dfa to Dfb and Cfb to Cfa) or across other climate zones (e.g., Dfb [continental warm-summer humid] to BSk [dry, cold semi-arid] and Cwa [temperate] to Am [tropical]). These shifts may result in lower efficiency for the current GBGI in the future. Given the importance of multiple services, it is crucial to balance their functionality, cooling performance, and other related co-benefits when planning for the future GBGI. This global GBGI heat mitigation inventory can assist policymakers and urban planners in prioritizing effective interventions to reduce the risk of urban overheating, filling research gaps, and promoting community resilience.

Toxic politics: Acting in a permanently polluted world.

Toxicity has become a ubiquitous, if uneven, condition. Toxicity can allow us to focus on how forms of life and their constituent relations, from the scale of cells to that of ways of life, are enabled, constrained and extinguished within broader power systems. Toxicity both disrupts existing orders and ways of life at some scales, while simultaneously enabling and maintaining ways of life at other scales. The articles in this special issue on toxic politics examine power relations and actions that have the potential for an otherwise. Yet, rather than focus on a politics that depends on the capture of social power via publics, charismatic images, shared epistemologies and controversy, we look to forms of slow, intimate activism based in ethics rather than achievement. One of the goals of this introduction and its special issue is to move concepts of toxicity away from fetishized and evidentiary regimes premised on wayward molecules behaving badly, so that toxicity can be understood in terms of reproductions of power and justice. The second goal is to move politics in a diversity of directions that can texture and expand concepts of agency and action in a permanently polluted world.

Political airs: From monitoring to attuned sensing air pollution.

In Madrid, as in many European cities, air pollution is known about and made accountable through techno-scientific monitoring processes based on data, and the toxicity of the air is defined through epidemiological studies and made political through policy. In 2009, Madrid's City Council changed the location of its air quality monitoring stations without notice, reducing the average pollution of the city and therefore provoking a public scandal. This scandal challenged the monitoring process, as the data that used to be the evidence of pollution could not be relied on anymore. To identify the characteristics of some of the diverse forms of public's participation that emerged, I route theories of environmental sensing from STS and feminist theory through the notion of attuned sensing. Reading environmental sensing through processes of attunement expands the ways in which toxicity can be sensed outside of quantitative data. This mode of sensing recognizes how the different spontaneous attunements to and with air pollution and the scandal acknowledged Madrid's chemical infrastructure, rendering visible qualitative conditions of toxicity. This mode of sensing politicized the toxicity of the air not through management or policy making, nor only through established forms environmental activism, but through contagion and accumulation of the different forms of public participation. All together, they made air pollution a matter of public concern. They also redistributed the actors, practices and objects that make the toxicity not only knowable, but also accountable, and most importantly, they opened up spaces for citizen intervention.