Updated: Jan 12
In recent decades our cities are going through intense process of urbanization. While urbanization have many benefits such as stronger economies and better facilities, it brings with it major challenges.
One of the biggest challenges coming alongside urbanization, is the Urban Heat Island effect (UHI). This climatic effect in cities basically means that the cities we live in are getting much hotter due to intense human activities. The denser and more populated our city becomes, the hotter it is while having bigger climatic impacts. Tel Aviv city for example, is +3°C on average hotter than its rural surroundings.
By 2050, approximately 7 billion people (~90% of the world population) will be living in urban areas.
This rapid change already has immense implication on our lives. Two thirds of the world’s energy is being consumed in cities, and they account for more than 70% of the total carbon emissions in the world. Therefore, the cities we are living in, are major drivers of climate change.
The hotter the heat island of the city:
More anergy is being consumed for air conditioning.
More greenhouse gases and CO2 are being emitted to the atmosphere.
Billions of dollars are being wasted on cooling the city down.
Accumulation of direct negative effects on human health and well-being.
Thermal Image of urban landscape during noon time, summer in Israel.
The temperature of surfaces in the city such as asphalt, concrete and even sun shades are reaching to around 50°C. This is because all of these artificial materials are absorbing solar radiation and emit it back to the city as heat.
All of these negative implications of urban heats islands in cities can be mitigated and solved by greening up our cities.
Plants have important cooling mechanisms. Firstly, they reflect the sun radiation back to the atmosphere and prevent it from heating urban surfaces.
Secondly, they evaporate large amounts of water to the atmosphere (97% of the water uptake by the roots).
During the process of photosynthesis and carbon fixation, plants are evaporating water molecules through their leaves during day time. This process is called water transpiration, and is necessary for the plant’s growth through photosynthesis.
By evaporating water which results in increased humidity and a decrease in temperatures, plants cool their environment and create micro-climate around them. This important quality of plants can be utilized in our cities in order to create biological shade and cool down the urban environment for the benefit of its citizens.
Other benefits for greening up the city:
Reduction in CO2 and GHG emissions
Increased urban sustainability
Air quality improvement
Increased urban Biodiversity
Creating green areas for physical and mental health
Higher extent of vegetation cover and increased plant biomass in our cities can create a significantly cooler micro-climate on small scale, and mitigate the urban heat island of the city and its negative effects on large scale.