I love seeing trees in more places, but for parking lots in particular they do have some downsides compared to solar panels. They often require more space; they attract birds that that poo on vehicles; and there’s a higher risk of collateral damage during windstorms. Not to mention that solar panels directly produce electricity, of course.
We absolutely should see more trees in many cities, but they introduce their own challenges in parking lots, especially if they’re placed retroactively.
I think this is a tree density problem. Most cities have a small number of trees, and they’re almost always over cars. These are trees that line streets and parking lots. Without trees, birds just have telephone poles and wires, which are also over the cars.
In San Francisco, we have a lot of trees on most of our streets, and many parks small and big, all full of trees. This means birds spread themselves out everywhere, not just over cars.
I think the true barrier to getting more trees is that individuals tend not to want to pay for and maintain trees. This includes caring for the tree, trimming it when it gets bigger, and cleaning the pollen, leaves, fruits, and branches that fall.
They also have the annoying habit of pushing concrete out of their way as they grow, and not just sidewalks. At my house we developed a water leak because the main waterline was 1 foot away from a tree. I don't know which came first, the tree or the waterline, but surely someone realized they were too close together, but they put them there anyway. Fast forward 50-100 years and the tree roots got bigger and ripped up the line.
Trees can cause a lot of trouble if you don't give them enough space to grow. "Enough space" depends on the kind of the tree, but it's typically similar to a parking space. You can mandate trees, but then you'll get less parking.
People always end up petitioning for them to be cutdown because tree litter inevitably falls on cars. The best solution for cars is dense multistory parking.
In South Korea, you usually don't see parking lots the size of several football fields like in the U.S., even around venues that generally attract a lot of cars, even in suburban areas. Instead, there are several stories of parking lots under every large building. Above-ground space is simply too valuable to waste on parking.
Unfortunately, you can't install solar panels underground.
They both are in competition for surface exposed to the sun. The mall’s parking lot near my place used to have trees. When they installed the solar panel shaders last year they cut down all of them.
The solar panels go over the parking spaces, like a kind of a bridge, with supports at the sides. There's a lot of space in between.
If the trees were in the same space as the panels, they'd be in the midddle of the parking space. What you'd have then is not a car park, but just a plain ordinary park.
I’m not sure to understand the design you’re talking about. The one I usually see have big supports each ~10/20 parking spot and the roof cover the spots but also overhang them by a few meters. Almost all space is exploited and you basically can’t see the sun anymore, which is the intent I suppose.
Notice how there are trees planted on the grassy strips between the rows of parking?
The solar panel supports take up a parking space at each end of the rows of bays with a lot of gaps in between.
Google Streetview is from 2009 - nothing newer, weirdly - but if you nose about you'll see what an insanely cool building it is. You can walk around in those roof gardens.
That’s a well-designed lot and very cool green-roof building indeed! I would love to work there! But it serves a very different context and real-estate economics than the high-density examples linked by Troupo. A suburban insurance HQ in a mid-sized city doesn't face the same constraints as a retail hub in a capital. The target demographics and land pressure aren't comparable.
In your example, they could have likely built the solar array on the large lawn to the north for much cheaper and with easier maintenance. The fact that they chose this integration suggests that cost was secondary to corporate signaling and employee experience [0]. For most parking lots density isn't a design choice, it's a financial necessity.
The one I was talking about (still on construction) targets a working class suburb. The few trees were tightly packed between the parking spaces and the new roof's supports are as well placed mostly in-between spots. They cuter the tree because the shade and the impossible maintenance. The shaded rosebush were kept but are now dying.
edit [0] Indeed, the roofs are part of their "Transition Plan" > As a key part of our ambition to consume 100% renewable electricity, Aviva has taken a significant step by installing a 1MW wind turbine at its Perth office in October 2024 In combination with our existing solar car ports and rooftop solar, the turbine will fully power the Perth office with 100% self-generated renewable energy for the majority of the year. It is expected to generate 1,700MWh annually, the equivalent to the electricity required to power over 620 homes. https://static.aviva.io/content/dam/aviva-corporate/document...
> If the trees were in the same space as the panels, they'd be in the midddle of the parking space. What you'd have then is not a car park, but just a plain ordinary park.
Sigh No, it's not. You can, and you should have trees in the middle of parking lots.
More trees often means less density which leads to worse cities. There is a place for trees, but 'more is better' is not true, especially around a parking lot which has already dropped the density massively. A parking lot is a city dead zone. Trees next to that will just expand that dead zone. It is like in the US where there are ornamental 'parks' at huge intersections. Nobody goes there. They didn't help. Same with parks around government buildings. SF is a great example of wasted space due to this. Generally, you need to minimize parking areas massively and then pack as much city next to them as possible to make up for the services they robbed. In the places where you actually do have exceptionally dense city then you can think about patches of green strategically placed. Getting a diverse, ecosystem like, city is the right approach but there is no hard and fast rule to get there.
Is there any constructive counter to my arguments? It is a great area to discuss.
We often think 'if a little is good then a lot is better' but clearly that isn't the case for basically every resource. Take the 'put trees everywhere' concept to the extreme and you have a forest, not a city. I am 100% in favor of putting trees and parks in a lot of city spaces, so long as it encourages the city and doesn't create or expand city dead zones. People should be using that green space regularly. Not their cars and the more infrastructure dedicated to cars and car support the less there is for people and people support. Trees in parking lots is car support, not people support. I have never once in my life wanted to drive to a parking lot for the trees in it and rarely want to take mass transit or walk to a parking lot next to a park since I would rather a park that has great restaurants and other services near it, not a bunch of concrete for cars. You have to minimize the impact of a parking lot quickly to get use out of it. Expanding its footprint with trees isn't doing that, it is actively making things worse.
Everything south of San Francisco is either leaf-shaded or a shithole, and anyone who drives through California can see this stark discrepancy for themselves.
We absolutely should see more trees in many cities, but they introduce their own challenges in parking lots, especially if they’re placed retroactively.