Urban Greening as a Way to Reduce Temperature Under Climate Change

Introduction

Cities warm up faster than surrounding rural areas — a phenomenon known as the urban heat island effect. In the context of global warming, the increasing frequency and intensity of heatwaves pose a critical risk to public health and urban infrastructure. In densely built-up areas, most surfaces are covered with asphalt, concrete, and other dark materials with low albedo (a measure of how well a surface reflects sunlight). These materials absorb solar radiation and retain heat for long periods, unlike soil or vegetation, where a significant portion of energy is used for water evaporation. Moreover, the high density of buildings and narrow streets creates so-called “heat canyons,” where heat is trapped and air circulation is limited.

According to a study based on satellite imagery and land cover maps analyzed in ArcGIS, impervious surfaces in Tashkent occupy about 78% of the city’s total area (Fig. 1). This means that nearly four-fifths of the urban territory absorbs solar radiation instead of reflecting it back into the atmosphere. As a result, nighttime temperatures in these zones remain significantly higher than in suburban or green areas.

The low albedo of built-up zones causes most of the solar energy to accumulate within the urban environment, intensifying air overheating and forming stable pockets of elevated temperature. This, in turn, increases the demand for air conditioning, energy consumption, and reduces overall living comfort — especially under accelerating global warming.

Urban greening is among the most accessible nature-based solutions for mitigating urban overheating. It provides not only localized cooling but also ecological and social benefits.

How Plants Cool the Urban Environment

According to reports by the Intergovernmental Panel on Climate Change (IPCC, 2022), green infrastructure is recognized as a key tool for enhancing cities’ resilience to climate risks. Trees also address multiple targets outlined in the United Nations Sustainable Development Goals (UN SDGs, 2023): they purify the air, reduce noise levels, preserve biodiversity, and improve human health and well-being.

Modern approaches to urban greening increasingly rely on the concept of urban forestry. One widely cited practical guideline is the 3–30–300 rule, proposed by urbanist Cecil Konijnendijk: from every window, at least three trees should be visible; tree canopy should cover at least 30% of each neighborhood; and every resident should live no farther than 300 meters from a park or green space (Konijnendijk, 2021). This principle underpins large-scale “Million Trees” programs in cities such as New York, Paris, Shanghai, and Uzbekistan.

Main Mechanisms of Vegetation Cooling:

The primary cooling mechanisms of vegetation include several interrelated processes:

1. Shade protection. Tree canopies block sunlight and reduce the heating of buildings, sidewalks, and roads.
2. Evapotranspiration. The evaporation of water from leaf surfaces removes thermal energy from the air. This can lower air temperature by 2–4 °C, and in dry climates even up to 6 °C.
3. Changes in albedo and thermal inertia. Green surfaces reflect more sunlight and warm up more slowly than dark asphalt and concrete.
4. Planning and spatial effects. Large parks generate “park breezes” — flows of cooler air that spread into surrounding neighborhoods. Green streets also help reduce local heat peaks.

Figure 1 The urban heat island effect

Figure 2 The urban heat island effect

Throughout the day, the cooling effect of trees changes. During daytime, shading and moisture evaporation dominate, while at night, canopies partly retain the heat released from the ground. Therefore, the strongest temperature reduction occurs in the afternoon, while moderate cooling is maintained at night.

Overall, with well-chosen species and thoughtful placement of greenery, urban air temperature can decrease on average by 10 °F (≈ 5–6 °C) or more (NASA, 2023). This makes greening one of the most accessible and effective ways to adapt cities to climate change.

Figure 3 Mechanisms of how urban trees mitigate the urban heat island effect and cool the air

Co-benefits (Why It Is Economically and Socially Beneficial)

• Reduced energy consumption for cooling. Properly placed trees and green spaces can significantly lower electricity use for air conditioning. Estimates for individual homes and neighborhoods show savings of around 20–30%, depending on climate and tree location.
• Mitigation of the urban heat island effect / Role of green infrastructure. Environmental agencies and urban adaptation studies describe in detail how trees, green roofs, and vegetation reduce surface and air temperatures (through shade and evapotranspiration), thus easing pressure on energy systems and enhancing cities’ climate resilience.
• Reduced heat-related illness and mortality. Recent studies and meta-analyses show that expanding tree cover and green spaces can substantially reduce health risks during heatwaves. Modeling results indicate significant — sometimes double-digit — reductions in heat-related mortality with increased canopy coverage (values vary by city).
• Improved air quality. Vegetation influences local concentrations of particles and gases through physical filtration, deposition on leaves, and local micrometeorological effects. EEA reports and thematic reviews on vegetation’s impact on air pollution provide quantitative assessments and recommendations for using green belts as part of air quality improvement strategies.
• Increased neighborhood attractiveness and economic benefits (impact on property value). Research and reports indicate that proximity to parks and high-quality landscaping often raise property values in the area — typically by 7–10%, and in some cases up to 20% for especially desirable locations.

Situation and Research in Uzbekistan (Case of Tashkent)

Tashkent today is one of the fastest-urbanizing cities in Central Asia, and it is here that the effects of warming are felt most acutely. According to satellite data and recent environmental assessments, over the past five years the city’s overall “greenness” has decreased by approximately 33%. The sharpest decline has been recorded in central districts: Shaykhantakhur — by 26%, Yakkasaray — by 23%, Almazar — by 33%, and Mirzo-Ulugbek — by nearly 18%. These figures confirm that dense construction, replacement of old trees, and insufficient systematic maintenance of green areas directly lead to the loss of natural shade and an increase in urban temperature. (Kun.uz)

The reduction in green space coincides with the rise in construction density and active development of remaining open areas. Along many streets, felled trees are replaced with lawns and shrubs that visually create a sense of “greening” but fail to provide the same climatic benefits. As a result, during the hot season, air temperature on treeless urban streets can exceed background values by 5–7 °C, adding extra heat stress on both public health and infrastructure.

In response to these trends, city authorities are implementing large-scale programs to restore and expand green zones. By 2030, the total area of parks and public gardens in Tashkent is planned to increase fivefold — from about 900 hectares today to 5,000 hectares. Each new sapling will receive an individual “passport” and a designated caretaker. Starting in 2024, the city began expanding green zones annually — first by 300 hectares, then by 1,000–1,400 hectares per year. According to the General Plan of Tashkent until 2045, the total area of green spaces should grow by 10,000 hectares, and a “green belt” of 15,000 hectares will be established around the capital. This will increase green space per capita from 5 m² to 8 m², although even these figures remain below the average for sustainable megacities, where the indicator often exceeds 20 m² per person.

However, alongside these ambitious plans, worrying tendencies have also emerged. In recent years, parts of green areas have been transferred into private ownership or developed for commercial purposes, raising concerns among ecologists and residents. The lack of transparent data on tree-cutting permits and weak control over the preservation of mature trees create the risk that “greening” could become merely decorative — unable to genuinely reduce temperatures or improve the city’s microclimate.

Scientific studies confirm that it is not the quantity but the quality of green spaces that determines their cooling potential. In the study “Green Spaces for Summer Cooling: Case Study of Tashkent” (Mukhamedjanov, Isamukhamedova & Tang, 2024), thirty green zones across the capital were examined. Researchers measured air temperature, humidity, and other parameters during warm months and found that maximum cooling occurs in areas where tree canopy shade covers more than 75% of the surface. These are the true “cool islands” — where daytime air temperature can be several degrees lower than on nearby streets. Example of temperature differences in green and non-green areas of Tashkent, summer 2022 (Fig. 5).

Figure 5 Example of a green area with low temperature

The study showed that lawns and shrubs provide almost no cooling effect — they can serve an aesthetic purpose, but not a climatic one. The optimal results are achieved with trees at least 7 meters tall, featuring dense crowns and consistent shading. However, overly dense planting without sufficient air circulation can have the opposite effect, retaining heat at night and reducing the overall cooling benefit.

Researchers also warn that between 1990 and 2019, the built-up area of Tashkent increased by nearly 60%, while the area of green vegetation decreased by roughly the same proportion. This transformation of the city’s spatial structure is directly linked to the urban heat island effect — the rise in temperatures within densely built areas compared to suburban zones. Therefore, new greening programs must consider not only the number of trees planted but also the spatial distribution of shade, air circulation, and species selection.

A Simple Roadmap for Urban Practice Implementation

To mitigate the impacts of urban overheating and restore natural balance, urban policy must include a systemic approach to planning and maintaining green infrastructure. Such an approach begins with mapping “hot spots” — the analysis of satellite imagery and local temperature data helps identify areas facing the greatest heat stress and vegetation deficit. Based on this data, targeted district-level greening plans are developed, setting clear priorities and quantitative targets for expanding green coverage.

The next step involves selecting species and planting designs that account for climate conditions, water resources, and ecosystem functions — from providing shade and reducing surface temperature to improving the microclimate and supporting urban biodiversity. Equally important is ensuring institutional sustainability: integrating greening into urban planning regulations, climate adaptation strategies, and beautification programs, while securing stable funding not only for planting but also for regular maintenance.

The final element is monitoring and evaluation. Tracking changes in temperature, canopy coverage, air quality, water use, and social perception helps refine and enhance the effectiveness of interventions. This integrated approach makes urban spaces more resilient, comfortable, and economically beneficial for both residents and businesses.

Conclusion

Urban greening remains one of the most effective and accessible nature-based solutions for mitigating urban heat. Research shows that a well-planned network of greenery — including street trees, parks, courtyards, and green roofs — can lower urban air temperatures by 1–4 °C. This is particularly vital for densely populated and heavily built-up districts, where the urban heat island effect is most pronounced. In addition to direct cooling, vegetation increases air humidity, improves air quality, and enhances overall urban livability.

However, the effectiveness of green infrastructure largely depends on a systematic approach. Planting trees alone is not enough — greening must be guided by data-driven planning and mapping. Modern remote sensing techniques, including satellite imagery, make it possible to identify hot zones — areas with high surface temperatures and low vegetation density. These zones should become the top priority for tree planting.

It is equally important to ensure proper species selection and long-term care. In arid climates such as those of Tashkent and other Central Asian cities, preference should be given to native and drought-tolerant species that require minimal irrigation and are well adapted to extreme temperatures. Regular maintenance, pruning, monitoring tree health, and watering are key components of sustainable green infrastructure. Only with such an integrated approach can greening become not a temporary campaign, but a long-term climate strategy, delivering environmental, social, and economic benefits.