Trees are green, right? And green is good, right? So trees must be good, right?
How could trees be bad for the environment?
Many of us have a sense that we are not on the right path; in our bones we feel the damage we do to this planet really does matter.
And often we cling overzealously to charismatic symbols like trees and honeybees, and lose sight of the place of the symbols within the system.
Cities are trying to respond to increasing environmental pressures. For example, to reduce dependence on agricultural breadbaskets at risk of climate change-induced droughts, cities are promoting local and urban agriculture. To reduce use of climate-changing fossil fuels, cities are promoting renewable energy. These efforts are distinctly urgent as we head for 410 ppm of atmospheric CO2—remember that 350 ppm gives only a reasonable chance of maintaining a climate conducive to advanced civilization.
And trees throw shade on those efforts.
We need a Right to Light.
There is historical precedent here, and various jurisdictions have Right to Light legislation—usually used to make sure a new building does not shade your windows and turn you into a shivering ball of moss—but cities that want to be leaders need to make sure solar panels and gardens have as many rights as condo towers.
Sunshine is the renewable energy that is delivered right to your house every day, right to your vegetable patch and your solar hot water collector.1 Before electricity turned every building into a faceless box, architects designed both for daylighting and ventilation. Well-insulated buildings can get a great proportion of their heat and light from sunshine coming in the windows.
Unless you have a great big tree in front of you.
Street trees are more than just comforting tokens; a dense green canopy that helps us forget the moonscape clearcuts that supply us with paper and lumber. Trees do a lot for our cities; they slow and clean stormwater, they remove air pollutants, they look nice and appeal to our old evolutionary psychology, to name just a few. 2 Urban trees should be seen as infrastructure alongside the pipes in the ground and the roads we ride on.
But the City of Victoria, where I live, protects certain native species and all very large trees—unless of course you want to put in a driveway, or build an addition on your house. You have no rights if you want to cut trees shading your solar collectors or vegetable patch, but if you want a place to park your Hummer, let the chips fly.
The City of Vancouver plans to plant 150,000 new trees, but unless a systems perspective is incorporated, they are planting 150,000 new problems and a forest of lost opportunities.
Here is how I think our urban tree system should work:
Trees are important habitat for myriad species. They look nice, and humans are hardwired to feel better, and perhaps be healthier when they can see trees. In cities they have the important job of shading asphalt to reduce the urban heat island effect. Trees can also provide tons—or on the scale of a city, tens of thousands of tons—of fruit and nuts.3 This would mean jobs for urban orchardists, food processors, farmer’s markets and foresters. It would also increase urban resilience to disasters by enhancing food security, and reduce the ecological impact of food transport.
And they can do all that on the south side of the street.
Let’s keep it simple by imagining a street that runs east-west. Trees planted near the sidewalk on the south side of the street will shade the blacktop, but not the garden on the north side of the street. Not the solar hot water collectors, not the windows that brighten life, not the photovoltaic panels, just the blacktop.
That is our infrastructure working for us.
This does not mean we will have fewer trees, it just means we will incorporate our Right to Light into urban design. It means we will not plant trees where they will block light and preclude energy harvesting with plants or panels for decades to come.
So, as infrastructure, when trees no longer serve the city they should be dug up, dynamited, moved or replaced. 4 We don’t remains slavishly loyal to our old pipes and our leaking sewers. We don’t worry about hurting the feelings of our bridges and sidewalks. When our trees are preventing us from accomplishing other goals—goals much more important than a new parking spot—then it is time for them to move.
Data wormhole for those who enjoy such things:
In Canada’s ‘Household Sector’ about 40% of our energy is burned by our cars and 60% is burned by our homes. 60% of that 60% is used for heating our homes and water. So about a third of our total personal energy use is just heating.
Of the third of our energy use that goes to heating, about 60% is fossil fuels.
-Of the 40% share of electricity, 40% of that actually comes from burning coal and and natural gas. The remaining 60% is hydro and nuclear. And nuclear is not renewable. So actually, a large proportion of the energy that keeps the lights on and keeps us warm is non-renewable.
And here is a proposal for a solar hot water system that notes trees are blocking some of the insolation.