The Importance of Being an Urban Tree.
- Jennifer Kenix
- 7 hours ago
- 3 min read
Have you ever heard of Nature Prescriptions? Water Cycle Regulation? Phytoremediation? Urban Heat Island Effect?
They might sound like reality TV shows or Council jargon, but these are just a few powerful ways humble urban trees impact our lives, homes, and communities. Trees do far more than we give them credit for: helping fight climate change, cleaning pollutants from the air, and most importantly, releasing the oxygen we need to breathe.
Let’s dig deeper into how trees support our health, gardens, and neighbourhoods...
Nature Prescriptions, aka Green Prescriptions (GRx), are when doctors recommend nature-based activities to improve a person’s physical and mental well-being. Being around trees and greenery has been shown to reduce cortisol levels (your stress hormone), lower blood pressure, ease anxiety, and support better mental health overall.
Water Cycle Regulation is how water is stored and moves through our environment. Trees play a major role in this. As they transpire (release water vapour), that moisture rises, cools, and forms clouds. When the clouds get heavy, it rains. Some rainwater soaks into the ground to recharge underground reserves, and the rest flows into rivers and oceans (runoff). Unfortunately, that runoff often picks up sediment, pesticides, fuel, and heavy metals along its way, thus polluting our waterways.
Trees help by intercepting rainfall with their leaves, slowing the water flow, filtering out pollutants, and allowing more of it to soak into the soil. This reduces how much dirty stormwater ends up in our rivers. For example, a large deciduous tree can capture more than 3,800 litres of rain each year in its canopy, and similar-sized evergreens can hold two to three times that amount. Their roots also stabilise soil and allow water to gradually filter into the ground, helping to top up groundwater supplies and reduce erosion. Trees can allow 250mm/hour to infiltrate the ground, a lawn only 100mm/hour, and a paved surface, virtually none.
Phytoremediation is another amazing natural process. This is when plants, including trees, draw water up through their roots, essentially filtering and cleaning water before releasing it back into the atmosphere. They either use the nutrients for plant growth or trap harmful chemicals in their wood. Without plants, these pollutants would end up polluting our water systems further.
The Urban Heat Island Effect happens when built-up areas are significantly warmer than nearby natural areas. That’s because concrete, asphalt, and buildings absorb heat and hold onto it, while trees and plants help cool things down through shade and transpiration. In addition to the cooling effects trees have in an urban setting, they provide this in our gardens by providing shade, air pollution removal, and reducing energy use in our homes.
In summary, trees offer incredible value to humanity and the natural world. Areas with more trees not only look better, they are often cooler, healthier, and have higher property values. With their vertical beauty and the benefits they bring to our lives, homes, and communities are undeniably hard to ignore.
Appendix: References
Health New Zealand: Green Prescriptions
ResearchGate: Health effects of green prescription: A systematic review
Penn State Extension: How Do Trees Reduce Stormwater and Flooding?
USDA Forest Service: How much rain can a tree retain?
ScienceDirect: Phytoremediation: Mechanisms, plant selection and enhancement
ScienceDirect: Cool surfaces and shade trees to reduce energy use and improve air quality in urban areas
GreenBlue Urban: How Trees Increase Property Values
Vibrant Cities Lab: Urban Trees Increase Home Values
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