All across the world, extreme temperatures have soared for weeks. From Japan to Europe, all the way to the US temperatures are responsible for the death of hundreds of people, sparking wildfires in souther European countries and displacing thousands of people due to fire risks.

All around the globe cities are under heat alerts, posing risks for those groups that are more vulnerable like the elder, people with health conditions, children and people living in areas not prepared for extreme heat.

Urban areas, that is cities and large towns are having the hardest time. With temperatures 5ºC to 9ºC warmer than rural areas due to concrete buildings and sidewalks absorb the sun and radiate back heat. Add to the equation mass transport, machinery and lack of shade and the center of cities are turning into living hells.

Politicians and governments see no other option but to acknowledge that we are going through a climate emergency and that urgent measures are required, and the short-term solution may just be simpler than some would like to believe.

How to keep cities and neighbourhoods cooler?

 Many cities around the world are taking bold steps to show that they can keep urban areas cool without buying into extra air-conditioning. One example is the Indian city of Ahmedabad.

The city implemented its Heat Action Plan after an extremely hot and deadly pre-monsoon season in 2010. The plan not only set up an early-warning system for the vulnerable. It included water supplies to the public, plants and trees and a “cool roof” initiative to reflect heat. Some 7,000 low-income households have had their roofs painted white, a simple measure that dramatically reduces inside temperatures by reflecting sunlight. The plan of the city of Ahmedabad is believed to save each year 1100 lives.

Cities like Amsterdam, Melbourne, Milan, Stockholm and Tokyo are great examples of governments pushing for greener streets to fight extreme heat in cities. Not only do these cities have shown already to lower by a few degrees the urban temperature, but business are thriving, people are happier and health of the people in these areas may just be increasing.

So, if your area and government hasn't joined the global movement of cities turning to trees and plants to offer cooler streets to its citizens, do write to your local government and constructively bring up that the solution may be simpler and more cost-effective than we think, the start of it all could be to bring the green back to our streets.

Can plants keep my house cooler?

Several studies have shown that plants in homes and workplaces help reduce stress, increase productivity, enhance employee attitudes, lower operating costs, help in “green building” design, and improve air quality. Although many of these studies involved workplaces, the principles apply to homes as well.

Although there is no extensive research on the effectivity of indoor plants helping to reduce temperatures considerably, by just applying the mechanisms by which plants work and some research, plants cool indeed help us get our homes cooler.

Since plants cool by the process of "transpiration", releasing moisture into the air, a USDA estimate by Dr.Leonard Perry is that  "proper use of plants could decrease air temperature in an office by as much as 10 degrees. Plus, the moisture released by these plants helps maintain indoor humidity in the human comfort zone of 30 to 60 percent".

Higher relative humidity will typically make a room feel cooler. People in climates with high levels of humidity may not notice the impact that plants have in the temperature feeling indoors, but those in drier climates may see how increased humidity will help cool a space.

Do plants filter the air at home?

In 1989, a team at NASA conducted its ‘clean air study’ to investigate the naturally filtering properties of plant life. NASA had conducted the study in response to the ‘sick building syndrome,’ as it came to be known late into 20th century. During that time, fresh air exchange in buildings was sacrificed in favor of reduced energy usage — to lower the cost of heating and cooling a building, interiors were super-insulated sealed air tight. This condition saw the rise of various illnesses transmitted due to the lack of natural ventilation and fresh air. At the same time, that era saw the use of synthetic building materials that gradually emitted harmful ‘off-gases.’ The team of researchers at NASA conclude that in addition to the use of safer building materials and the minimization of mechanical ventilation, indoor air pollution can be greatly mitigated by the introduction of ‘nature’s life support system,’ plants.

The NASA study concluded that certain plants are very efficient and effective natural air filters to remove organic air pollutants. Accounting for chemicals like benzene, formaldehyde and trichloroethylene the researchers recorded the percentage decrease of pollutants. This study opened a new way to see plants indoors, beyond just helping design more human spaces and increase subjective well-being together with productivity they also help people stay healthier and away from specific deseases.

What plants filter out indoor air pollutants?

Based on different research studies, like the NASA's "Interior Landscape Plants for Indoor Air Pollution Abatement" in 1989 the following list of plants show you the most effective plants that will help you make the air in your workplace or at home cleaner:

• English Ivy (Hedera Felix)
• Devil's Ivy, Pothos Plant ( Epipremnum Aureum)
• Peace Lili (Spathiphyllum Mauna Loa)
• Chinese Evergreen (Aglaonema Modestum)
• Bamboo Palm (Chamadorea Seifrizii)
• Snake Plant (Dracaena Trifasciata 'Laurentii')
• Heartleaf Philodendron (Philodendron Cordatum)
• Lacy Tree Philodendron (Philodendron Bipinnatifidum)
• Elephant Ear Philodendron (Philodendron Domesticum)
• Marginata (Dracaena Marginata)
• Cornstalk Dracaena (Dracaena Fragrans ‘Massangeana’)
• Weeping Fig (Ficus Benjamina)
• Aloe Vera
• Warneckii (Dracaena Deremensis)
• Banana (Musa Oriana)

We know that global temperature increase is not going anywhere anytime soon as the fight against global warming although urgent we are unable to solve it within just a few years, instead our civilisation requires of urgent measures for long-term impact. In the mean-time we can all push for change in our local areas, within our government and at home. If it is true that plants help keep our streets cooler and maybe also our living spaces, they also make people happier, more relaxed and healthier and that may be just as important to keep up with the journey towards sustainable living.

Remember, it is in your voice that resides the power of our time. Pass the knowledge to others, come together for greater impact and empower institutions, governments and people towards a more sustainable future. Tell us your initiatives how you are doing by tagging or messaging us at @weterrazero. 

Sources

- How cities are using nature to keep heatwaves at bay by UNEP

- As heatwaves blanket Europe, cities turn to nature for solutions by UNEP

- Interior Landscape Plants for Indoor Air Pollution Abatement by NASA

- Benefits of Using Plants Indoors by Dr. Leonard Perry