Tree-Solar Trade-Offs

Who knew trees could be so tricky? When looking for shade in a parking lot, I head for the trees. When seeking a place to hang a hammock, I look for trees. When wandering in the woods, I revel in the play of light through the leaves and branches. Trees, and the forests they inhabit, truly are the lungs of the earth. They absorb our poisons and release the oxygen we need to breath. Why then, given this reverence, would I advocate cutting them down in order to install solar panels?

To be clear, I love trees. I also love moving toward a 100% renewable future. If cutting trees allows me to reduce my personal and our collective dependence on toxic fuels, then it's something I am willing to consider, ​just as I am willing to consider altering mountain or ocean views in order to promote wind power (that's a different conversation). The fact is, I knew nothing about carbon sequestration when we cut dozens of trees to clear a view and to make room for more sun in 2004. It never occurred to me to do a cost-benefit analysis because I didn't know there was a choice. I loved trees from a distance, but hadn't really paid close attention to them.

Our goals were to create a soccer field for the kids, a vegetable garden, and a beautiful near and distant view. It's been almost 15 years and a lot has changed. We've planted a River Birch 'glen,' a bird-friendly hillside and a rain garden. We've installed solar panels and have a great lawn for all manner of sports. Each year, however, I become more and more curious about the trade-offs we made in order to create our own private Eden.

So here's what I've learned. On the most basic level, it's easy to plant new trees that serve multiple purposes but that won't block the sun. Fruit and nut trees, for example, absorb carbon and produce food. Flowering trees of all kinds provide nectar for pollinators and berries for birds. By cutting down all those evergreens all those years ago, we made room for a significantly more diverse landscape the provides food for us and a host of flying creatures.  

When I did some research, I learned the following about the tree-solar trade-off.  It takes 1.106 lbs of Co2 to produce 1 kwh of electricity so if you install a 5,000 kwh system, that would avoid 5,530 lbs of Co2 emissions each year. 

No two trees are the same: A 30 year old white oak absorbs 60 lbs of carbon a year; A white pine absorbs 193 lbs of carbon a year; A fast growing red oak can absorb 240 lbs of carbon a year. In Hanover and much of New England, we have a lot of white pines. 5,530 lbs/193 lbs = 28.65 trees. If you cut less than 28 trees to maximize your solar options, don’t feel guilty in terms of carbon absorption and avoidance - - If you are cutting white pines. 

I'm a photographer who loves trees and light. I'm also a gardener who loves backyard biodiversity and a world free from fossil fuel dependence. In my quest for a sustainable future for my family, I am constantly making trade-offs. We needed shade for our terrace and planted a tree whose maximum height is 30 feet, just below our rooftop panels. I had wanted an elegant oak, but needed to compromise as oaks get too large and would shade our rooftop panels.  Who knew we would now have more than 15 varieties of trees on our property where before we just had white pines and a few oaks?

In July, we considered electric lawn care and the many alternatives to gas-powered machines, including reducing the actual size of your lawn. This month, we continue the lawn care theme, but address it from the point of view of the trees and solar power. Both absorb the light. Both generate energy from that light. At the moment, however, we need to maximize the rate at which we transition to renewables. If that transition necessitates cutting some trees, I am willing to do so, especially if that creates more light for more diverse plantings and clean energy.   

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Sources:
Tree Facts: Arbor Environmental Alliance
Tree Math: New England Clean Energy (Tree Math 2, Sept. 2015)
Sierra Club: Hey! Mr. Green Should I Cut? (November 2016)