Trees save energy in many ways; solar panels only produce electricity. Their shade provides the obvious savings, but trees also slow winds and cool the surfaces of a city – all of which reduce demand for electricity.
If we recognize the savings and prioritize the importance of the canopies that trees create, then planting trees would be given a far greater value when designing city spaces than is currently the case.
Too often, large trees are removed or pollarded (pruned to a smaller-than-natural size) – and the need is justified because of the efficiency of solar panel installation.
If the economic benefits of large or medium size trees* were considered, then the decisions made about how to live with trees around our homes and streets would be revised to always include a continuous, 50-60% + canopy cover as part of all city designs.
*Check out our ‘Top Trees Under 10m’ series, featuring 40 favourite trees for urban home landscapes (Zone 5)
Most cities around the world now consider 25% canopy an ‘achievable’ number – yet struggle to approach that percentage, let alone keep to that target. Often, to claim this canopy cover of 25%, the reported figures include naturalized areas passing through a city – areas which are actually recreational – albeit with some homes nearby.
Then there are all the other benefits of a widespread city canopy: habitat for nature in our streets and gardens, the physical health benefits of shade and ‘forest bathing’, the increased social connectedness, and a reduction in crime.
These benefits are present at each moment and are long lasting – rooftop solar panels are expensive to install and lose efficiency over time, whereas trees provide their benefits for hundreds of years.
A tree structure and its leaves store energy and do their best to sequester the carbon dioxide produced by us all. They also transpire moisture into the air, which is both cooling and beneficial for our breathing.
Additionally, dust and other pollutants are physically attracted to the foliage of trees and then deposited from the air when the rain comes. A cooler city surface attracts more frequent rainfall (as happens in equatorial forests where late-day rains happen daily) with the moisture transpired into the air returning as rain in the cool of evening.
A compromise is to plant trees whose natural growth is only to 10 metres – but also which have a full width of canopy, normal life expectance and provide most of the benefits that trees offer to a city.
Then, solar systems can be installed on residential house roofs, without compromising their efficiency.
The many benefits of having trees around our homes outweigh the benefits of having a solar system that only generates energy during daylight. There are many open areas beyond the city that can generate the power needed to support the benefits that a full canopy would create for a city.
Because of the benefits trees provide – especially in reducing our need for electricity – prioritizing solar panels over trees in home designs is not a reasonable economic argument.
Tree canopies around our homes have so many gifts to offer – while solar panels offer only one. 🏡