Dataset Information

Global climate-driven trade-offs between the water retention and cooling benefits of urban greening.

ABSTRACT: Urban greening can potentially help mitigate heat-related mortality and flooding facing the >4 billion urban population worldwide. However, the geographical variation of the relative combined hydrological and thermal performance benefits of such interventions are unknown. Here we quantify globally, using a hydrological model, how climate-driven trade-offs exist between hydrological retention and cooling potential of urban greening such as green roofs and parks. Using a Budyko framework, we show that water retention generally increases with aridity in water-limited environments, while cooling potential favors energy-limited climates. Our models suggest that common urban greening strategies cannot yield high performance simultaneously for addressing both urban heat-island and urban flooding problems in most cities globally. Irrigation, if sustainable, may enhance cooling while maintaining retention performance in more arid locations. Increased precipitation variability with climate change may reduce performance of thinner green-infrastructure more quickly compared to greened areas with thicker soils and root systems. Our results provide a conceptual framework and first-order quantitative guide for urban development, renewal and policymaking.

SUBMITTER: Cuthbert MO

PROVIDER: S-EPMC8792007 | biostudies-literature | 2022 Jan

REPOSITORIES: biostudies-literature

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Global climate-driven trade-offs between the water retention and cooling benefits of urban greening.

Cuthbert M O MO Rau G C GC Ekström M M O'Carroll D M DM Bates A J AJ

Nature communications 20220126 1

Urban greening can potentially help mitigate heat-related mortality and flooding facing the >4 billion urban population worldwide. However, the geographical variation of the relative combined hydrological and thermal performance benefits of such interventions are unknown. Here we quantify globally, using a hydrological model, how climate-driven trade-offs exist between hydrological retention and cooling potential of urban greening such as green roofs and parks. Using a Budyko framework, we show ...[more]

PMID: 35082304

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Project description:The Paris Agreement promotes forest management as a pathway towards halting climate warming through the reduction of carbon dioxide (CO2) emissions1. However, the climate benefits from carbon sequestration through forest management may be reinforced, counteracted or even offset by concurrent management-induced changes in surface albedo, land-surface roughness, emissions of biogenic volatile organic compounds, transpiration and sensible heat flux2-4. Consequently, forest management could offset CO2 emissions without halting global temperature rise. It therefore remains to be confirmed whether commonly proposed sustainable European forest-management portfolios would comply with the Paris Agreement-that is, whether they can reduce the growth rate of atmospheric CO2, reduce the radiative imbalance at the top of the atmosphere, and neither increase the near-surface air temperature nor decrease precipitation by the end of the twenty-first century. Here we show that the portfolio made up of management systems that locally maximize the carbon sink through carbon sequestration, wood use and product and energy substitution reduces the growth rate of atmospheric CO2, but does not meet any of the other criteria. The portfolios that maximize the carbon sink or forest albedo pass only one-different in each case-criterion. Managing the European forests with the objective of reducing near-surface air temperature, on the other hand, will also reduce the atmospheric CO2 growth rate, thus meeting two of the four criteria. Trade-off are thus unavoidable when using European forests to meet climate objectives. Furthermore, our results demonstrate that if present-day forest cover is sustained, the additional climate benefits achieved through forest management would be modest and local, rather than global. On the basis of these findings, we argue that Europe should not rely on forest management to mitigate climate change. The modest climate effects from changes in forest management imply, however, that if adaptation to future climate were to require large-scale changes in species composition and silvicultural systems over Europe5,6, the forests could be adapted to climate change with neither positive nor negative climate effects.

Project description:Establishing urban greenspaces is an effective approach for improving urban air quality and thermal environments. However, at a finer scale, the potential mechanisms of urban greenspaces providing pollution retention and cooling benefits remain unclear, especially for the three-dimensional structural characteristics of plant communities. To explore the potential mechanisms, we conducted field experiments on 108 plant communities in Beijing and simultaneously monitored PM10 concentration data and meteorological data both within and outside the plant communities. We analyzed the relationships between three-dimensional structural characteristic factors, the pollution retention benefit, and the cooling benefit. The results indicated that the majority of the plant communities (90.91%) can simultaneously provide both benefits. The herbaceous layer was a crucial factor influencing the pollution retention benefit, with a nonlinear positive correlation between the pollution retention benefit and the ratio of three-dimensional green biomass of herbs and trees (RTDGB-HT) and a threshold of 0.80-1.00. The tree layer was a crucial factor influencing the cooling benefit, as indicated by a positive linear correlation between the cooling benefit and the ratio of three-dimensional green biomass of trees (RTDGB-T). With changes in three-dimensional structural characteristic factors, the rate of change in pollution retention benefit factors was 3-5.5 times that in cooling benefit factors. Mediation analysis confirmed the trade-off between the pollution retention and cooling benefits, with trees indirectly enhancing pollution retention benefit by reducing the daily mean temperature reduction rate (R-Tmean) by 20.44-22.27% and by reducing the daily maximum temperature reduction rate (R-Tmax) by 13.14-15.99%. Overall, 13-23% of the pollution retention benefit was achieved through reducing cooling benefit, and interventions involving extreme heat can minimize the trade-off between the pollution retention and cooling benefits compared to reducing cooling benefit throughout the day. Our findings enrich and extend the current understanding of the correlations associated with the comprehensive benefits at the plant community scale, emphasizing the differences in three-dimensional structural characteristics that provide different benefits, which can better inform the development of refined and scientifically managed strategies for green space renovation.

Dataset Information

Global climate-driven trade-offs between the water retention and cooling benefits of urban greening.

Publications

Global climate-driven trade-offs between the water retention and cooling benefits of urban greening.

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