Planting trees is one of the most effective ways to protect the life on the planet. Trees are a great nature based solution in many environmental and sustainability problems. Trees are in many ways the rulers, keepers and protectors of the world like the Ents are in The Lord of the Rings. We can say trees rule the climate. They are one of the main reasons that keep climate stable because they are one of the biggest carbon sinks and storages on Earth. In Lovelock’s Gaia hypothesis it was even suggested that the trees control the climate through their methabolism like a living organism. We know that the ecosystems work like organisms and they are like symbioses.

Trees are not only sequesting CO2 to make sugars but they also cool down the climate with evaporation and particles spreading from them. Evaporation is very important factor cooling down the weather and affecting climate locally and globally. University of Helsinki has made a lot of research on this. Some years ago we didn’t even know how crucial the trees are. We can see that all vegetation is important in cooling but especially the trees. The part of the trees from.cooling effect of vegetation is huge, over 90% and other plants 10%. Trees also affect strongly on local climate in urban areas. Some green areas without trees can be even warmer than the surrounding urban area, studies show.
Out of all the biomass on earth, which is about 600 Gt, 450-500 Gt is in forests. There are no organisms as massive as trees. And there is no larger carbon storage or sink than trees and the soil they create. Trees contain about 80% of plant biomass, or phytomass. The most soil on Earth is created by trees. Trees mitigate climate change and by that reduce the number of people dying in extreme temperatures. In urban areas there is not enough space for the vast forests needed to sequest enough carbon so it is especially important to protect the forests and trees in rural areas. The trees in cities are not enough to mitigate climate change but they are in a very important role in adapting to changing climate in cities.

Trees are our friends, biodiversity provides the services that nature offers us, i.e. ecosystem services from medicinal plants to water circulation and maintaining climate stability. Nature supports all life and human communities. When biodiversity collapses, human communities also quickly run into problems. Trees provide us with numerous ecosystem services, they sequest carbon, produce fruit and wood for use, provide nesting places for pollinators and pest-eating birds, trees shade and protect crops from the scorching sun and heavy rains, prevent floods, and the ionization of their leaves (that work on with electricity) cleans the air of impurities and pollution particles. 7 million people die mostly in cities because of poor air quality each year. The main reasons are burning coal, wood and fossil fuels and also traffic. Trees could save millions of lives by preventing extreme temperatures. Also by preventing floods that become more common because of changing climate they could save hundreds of thousands of lives.

Heat kills. Climate change kills already millions of people each year. Extreme weather is one of the biggest reasons why people die. Extreme temperatures kill more than 5 million people each year. Heat waves cause the most deaths. A heat wave in Europe in 2022 killed 60 000 people. It is predicted that the death tolls caused by hest waves will increase by 370 % in coming years. That means almost 18 million desths caused by heat waves. Over 125 million people are exposed to deathly heatvwaves each year and the number is increasing all the time because of climate change especially in the Global South where the people are also most vulnerable because of poverty.

Most of people who die because of heat waves live in cities and urban areas because there is a phenomenon called urban heat island. Urban heat island is caused by differen albedo in rural and urban areas, absorbing facets, different materials absorbing heat differently, urban canopy, anthropogenic hest escaping from buildings and anthropogenic pollution like CO2 and greenhouse gases, lack of turbulence and other smaller factors. Urban heat island can increase the temperature of the city up to 12 Celsius degrees compared to surrounding areas. Heat kills also by causing water shortage and destroying crops. Especially heat kill in the Global South but also even hundreds of thousands each year in the Global North. Most of deaths caused by heatwaves are occured in Asia.
We can save peoples lives with green infrastructure and vegetation, especially with trees in urban areas. Trees are one of the key factorsvin adapting to climate change. Trees are big and they evaporate a lot while sequesting carbon in photosynthesis. A big tree can evaporate even 40 000 gallons of water per year. That is 200 cubic meters. They release so much water in the atmosphere that cools down the local climate. Evaporating is a process in which the water is changing its from liquid to gas, water vapour. Plants and trees do that for lifting water into leaves. When evaporating they bind energy in the water from the atmosphere. Trees also give shadow for people, plants and animals.
The shadows can cool the climate for many degrees. Shades keep plants and animals alive, otherwise they would burn in the sun and die. They protect crops and water supplies. Trees also reduce air pollutants in the air locally and by that they reduce the temperature. Green infrastructure always needs also blue infrastructure because without water supplies there is no evaporation that cools the local climate. Vegetation and good healthy soil help to increase the amount of water. Without both water supplies and moisture the evaporation doesn’t work.

Trees can reduce the average temperature in European cities up to 1,1 to 2,9 Celsius degrees the studies show. Studies show that evaporation can reduce peak temperatures even 5 Celsius degrees. If we would increase the green coverage of the cities up to 30% the reduction in average temperatures could be even 5,9 Celsius degrees and in peak temperatures much more. Thos would decrease the number of death tolls in the heat waves in Europe by 2600 people thst is 1% of all summer time deaths. An analysis of satellite data from 293 cities in Europe has found that trees have a huge cooling effect in urban areas while other green spaces often don’t. They can be even warmer than surrounding city area. In Europe trees can decresase surface temperatures even 8 – 12 Celsius degrees. The tree canopy can lower the local air temperature by evaporation and shading up to 10 Celsius degrees. So difference can be like 30 degrees without trees and 20 degrees with trees. We can say that is a huge difference saving lives. Planting trees increases many crucial ecosystem services and decreasind the urban heat island is one of the most important. We must take this into account in city planning and increase the amount of green and blue infrastructure, especially trees.

Sources
The Guardian. 2021. Extreme temperatures kill 5 million people a year with heat-related deaths rising, study finds. https://www.theguardian.com/world/2021/jul/08/extreme-temperatures-kill-5-million-people-a-year-with-heat-related-deaths-rising-study-finds
WHO. 2023. Heatwaves. https://www.who.int/health-topics/heatwaves#tab=tab_1
EU. 2023. Increasing tree coverage to 30% in European cities could reduce deaths linked to urban heat island effect. https://environment.ec.europa.eu/news/increasing-tree-coverage-30-european-cities-could-reduce-deaths-linked-urban-heat-island-effect-2023-06-21_en
Ly. 2021. Trees cool the land surface temperature of cities by up to 12°C. New Scientist.
Weeden. 2023. 3 WAYS PLANTING TREES HELPS TO REDUCE THE URBAN HEAT ISLAND EFFECT. One Tree Planted.