In cities, the urban landscape creates warmer conditions than surrounding rural areas. Dark road surfaces and building facades absorb heat, dense construction slows wind flow, and limited vegetation reduces evaporation cooling. Vehicles, factories, and other heat sources add to the overall warming. Areas that become hotter than their surroundings are referred to as heat islands.
This intensified heating, which in some large cities can push temperatures 10 to 15 degrees Celsius above nearby regions, can affect health, especially on already hot days. Heat stress can increase the burden on the cardiovascular system and other organs. Cities often respond with measures that promote green and blue spaces, landscaping, and the creation of reservoirs to cool the environment.
However, research from scientists at the City University of Hong Kong, Xian Jiaotong-Liverpool University, and other institutions suggests these measures may have limited impact. They analyzed meteorological data alongside daily mortality in Hong Kong from 2008 to 2017. The study found that when the daily temperature rose by 1 degree Celsius above 29.61 degrees, mortality increased by 5.7 percent in areas with low landscaping, 5.4 percent in medium landscaping areas, and 4.6 percent in areas with high landscaping. Proximity to water showed similar patterns, with mortality rising by 7.5 percent in areas with little water and 3.5 percent where water is abundant.
The researchers concluded that the protective role of green and blue zones against heat-related deaths was not significant in Hong Kong. They posed questions about how strong such greenery is in reducing heat-related mortality. The study appeared in the journal Science of The Total Environment.
Dr. Boris Revich from the Institute of Economic Forecasting notes that findings from Hong Kong should not be generalized to other regions. He points out that this city’s unique geography, being a coastal area surrounded by mountains, creates complex air-flow patterns that may limit the cooling effect of green spaces and water systems. In regions with conditions similar to Russia, landscaping and reservoirs can yield positive results, Revich says. For example, Nur-Sultan in Kazakhstan has built a forest ring that helps mitigate extreme warming, a feature not easily replicated in every city.
In Moscow, the inner city tends to experience the highest temperatures, with reduced heat in the southwest and near parks and reserves such as Losiny Ostrov and Izmailovsky Park. Revich emphasizes the value of park infrastructure, noting that shaded areas and recreational options encourage people to spend time in green spaces, contributing to cooling effects. He cautions that green installations should have a clear protective function rather than simply be decorative. A case in point is a long boulevard where trees were planted for looks but did not form a continuous green barrier to block polluted and hot air from dense traffic. If trees lined the sidewalk edge more consistently, the surrounding air might stay cooler and cleaner.
When staying indoors during heat spells proves difficult, individuals often rely on cooling methods such as air conditioning and ample hydration. While these measures do not eliminate the cumulative effects of day and night heat, they can reduce the harm. Russian scientists estimate that reducing green areas while expanding housing would raise Moscow’s temperatures by 2050 by about two degrees above current averages, potentially increasing the likelihood of dangerous heat conditions amid ongoing climate change.
Gardening and tree planting are not just about climate regulation; they also help shield residents from pollution. In the Donetsk coal basin, trees selected for resistance to gas and dust are used in landscaping to improve air quality. Green spaces and water bodies contribute to urban climate stability and positively affect the well-being of residents. A broader study in an international journal of environmental science found that people living near forests and lakes during the COVID-19 pandemic experienced fewer anxiety and depression symptoms. Even simply looking out at trees and water from a window had a noticeable positive effect.