Are trees the lawns of the future?


The lawn started as a demonstration of excess, as I understand it. A lawn indicates that the landowner has enough land to let some of it serve no use, and the resources to manage the land. Lawns are, typically, a decadent waste of land and resources.

Of course, people play all kinds of fun games on grass. In private homes, backyard lawn fun emerged from the existence of lawns. Lawns weren’t invented so that people could play with lawn darts and the slip-n-slide. The lawn in the British estate emerged before polo, rather than the other way around. I would guess.

As an environmentalist, I’ve been trained to dislike lawns. They’re ugly, wasteful and bereft of biodiversity.

I can take a more subtle view of lawns when I learn that, when not heavily fertilized, they can sequester substantial amounts of carbon. I wouldn’t be shocked to find out that a lawn (or, as researchers call it, “turfgrass”) is capable of banking more carbon than an adjacent patch of forested land, depending on how both areas are managed. I don’t know if this is the case. (Most people with urban trees just collect up litterfall and don’t let any of its carbon mineralize into the soil, after all.)

Regardless of the carbon cycle, I’m not a big fan of lawns. Given the opportunity, I replace a lawn with native plants, which in California can be spectacular. Every kid should have a field in which to play sports, but it doesn’t have to be connected to one’s home.

Nowadays, I think it’s fair to say that most ecologists look at the proliferation of lawns throughout the United States as a waste of resources. Food isn’t grown where it could be grown. Residential plots may be too large to accommodate lawns. Over time, small pockets of natural areas i our cities have disappeared in favor of lawns. Lawns result in too much nitrogen and carbon pollution. In arid regions, lawns waste water.

Lawns squander our precious natural resources and are a scourge on the environment. That’s what many say, in our current time.

I wonder if, a couple generations in the future, environmentalists will be saying similar things about trees?

Don’t get me wrong: I love trees. I might even love trees as much as some people love their lawns.

I live in a city that’s known for having great trees. It isn’t entirely by accident that I chose to live in Pasadena. We even have tree police if someone chops down a tree illegally. I once called them on a neighbor who illegally removed a coast live oak that was at least 100 years old, and they had two agents on site within fifteen minutes. He paid a hefty fine. We take our trees seriously.

What do trees do for us, on the scale of our residential plots of land? Trees support plenty of biodiversity, even the towering pecan tree (not edible pecans, sadly) in my backyard. In a given day, at least several species of birds will perch on its branches. Commonly, it will also host a flock of feral parrots that roam through town. I think it’s part of the regular parrot circuit. It also casts a wonderful shade on the deck behind my house in the afternoon, and it supports half of the weight of a hammock. It’s a great tree. I like the oak tree in front of my house even more. Years after killing off the lawn surrounding the oak, I just found that the invasive ant inhabitants were replaced by a native species. That was a nice discovery.

However, while these trees provide services, they’ve also had a huge negative effect on me as well. They’ve kept me from putting solar panels on our roof. With the shade of these massive trees, it makes no rational sense to install solar panels. Of course, the trees mean that we don’t have to spend as much energy cooling our home in the summer – and the energy we use comes from electrons that arguably were generated by a wind farm (a privilege for which I pay 20% extra to alleviate my conscience).

While these trees are playing a role in carbon sequestration to some extent, the solar panels that could be used in place of these trees would probably result in greater carbon savings. My street, lined with oak trees, is gorgeous. This is a also a street filled with families that are carbon bandits, failing to generate electricity in an environment that is prime for the generation of solar power.

A gorgeous tree-lined street is a sign of prosperity and the luxury to be able to maintain such a show of status. We can afford to have trees in residential areas because we are wealthy enough to take carbon from beneath the floor of the ocean to power our appliances rather than use the same energy that feeds our trees.

As solar power gets even cheaper and even more efficient, then perhaps trees will be seen the way that we see lawns today? I don’t know if this will be the case, but if this comes to pass, I won’t be terribly surprised.

I grew up in a landscape which was inhabited by humans for some thousands of years, and large cities with dense populations for less than a hundred of those years. I’ve been spending the last few weeks – on vacation – in a landscape in which people have lived at high densities for thousands of years. It’s clear to me, in this environment where cities have exited for long periods, that trees are a luxury. Big tall trees, that cast a lot of shade, are not allowed to exist for their biodiversity value. They have the same role that lawns have arid North America. Trees are a symbol of wealth and also a form of beauty, and they also are nice to rest in under the shade. I imagine these trees also might provide more ecosystem services than a lawn, but are they better for the carbon cycle than a solar panel? I’m not sure. I spent some time searching and I couldn’t find the right data to compare lawns, trees and solar panels.

Of course, a landscape without trees has less biodiversity than a landscape with trees. Right? Would my city have lower biodiversity if it was not filled with towering trees, most of which weren’t there at the time of European settlement? If we had lots of native shrubs and annual plants in the place of these trees, would biodiversity be lower? I’m not sure. I don’t know if anybody’s evaluated this quantitatively.

I value trees for the services they provide, and their beauty. However, I ‘m not all that sure how much of the value that I assign is inflated by social context. Fine art masterworks sell for obscenely huge sums of money, and they only reason they are worth so much is because everyone who can afford them agrees that is how much they are worth. I recognize that the value that I place on trees is a product of my particular experiences and social context. It says something that our culture can afford to value trees for their beauty, when these same trees are sucking up photons that could generate electricity without contributing to the elevated pool of CO2 in our atmosphere.

Whatever happens in the future, I hope everyone’s values are more focused on carbon cycling than they are at the moment.

14 thoughts on “Are trees the lawns of the future?

  1. A thought provoking post, Terry. As a keen amateur gardener and a professional who has students who have worked on garden biodiversity projects, I’d have to say that there’s lawns and there’s lawns: it all depends on how they are managed and what the purpose of a lawn is. Clearly there’s a continuum from high diversity, natural “lawns” (i.e. close-cropped grassland which can support significant biodiversity) through to the high resource input, monoculture, perfectly presented lawns seen on golf courses and around important buildings. In the part of the continuum that you’re railing against, typical urban and suburban householder’s lawns and everything above, it’s possible to manage them in a low-input way that is both productive and can support biodiversity.

    In the house we moved into about 18 months ago, the garden was wholly laid to lawn. Since then we’ve dug flower borders, a vegetable patch and planted trees, but kept about 50% lawn (though this will reduce as we widen borders). We don’t water or fertilise the lawn, just keep it regularly mown. I’d estimate that, in addition to the grasses (some native, some not) there’s another 10 to 15 native plants growing in it, plus fungi which pop up every now and then. The plants include taxa which are popular nectar sources for bumble bees and solitary bees, e.g. clovers, dandelions, etc. These flower even though we mow regularly.

    I mentioned that the lawn is “productive” and that’s where the cuttings come in. They are either put into the compost heap, fed to our chickens, or added directly to the vegetable patch as a mulch.

    So I think it’s possible to have a lawn that adds to local biodiversity and is productive for the gardener, but I accept that we may be unusual in that regard.

  2. Hmmm, interesting post. As a European with a stereotypic view of urban planning in the US, the answer seems obvious to me: live closer together! The trees can stay where they are and you can have a solar panel. Also, you can do your communiting by bicycle (reducing environmental strain) because you don’t have to stretch insane distances to get anywhere, because everything will be much closer by if housing distances are reduced. You can grow your vegetables on your balcony and play football in the park.

  3. As to carbon sequestration, this must be higher for forests: they intercept nearly all light falling on them (otherwise there would be grass beneath it) and organic matter accumulates for at least a meter depth. This won’t happen in grassland/meadow.

  4. Do lawns actually capture less light than forests? It’s hard to measure how much light would pass through a green layer of a lawn. And, there is a higher turnover rate belowground, isn’t there, because the grass is more decomposable than forest litter? (I’m not an ecosystem person, though I’ve played one on occasion.)

  5. So, these thoughts were coming to be because I was in Europe. It was so obvious to me, spending time in places with different levels of wealth, that only the well-off places choose to stay forested, or have nice street trees. It’s not because people haven’t been there long enough to choose to have trees, but only the wealthy can really afford to have them, I think.

  6. I’m a geologist, not an ecologist, but it seems to me that your comments about trees depends on the part of the country (or world). In the northeastern and upper midwestern parts of the country where I’ve spent most of my life, it requires very little input to keep trees growing. And everything I’ve read indicates that they contribute a lot in terms of ecosystem services (cleaner air, less surface runoff, slight drawdown of CO2, lessens urban heat island effect).

    But I think your comment about wealth and urban trees is true. Poorer areas of a couple of cities I’ve lived in have been pretty sparse in terms of trees. It’s often because some blight came through and wiped out the previous street trees and those neighborhoods don’t have enough money/political clout to plant more trees. If new trees were planted, they’d grow without much work but taking that initial step hasn’t happened.

  7. Agreed – in places with more sunlight, and are more xeric – such as Southern California where I live, I think they might be of less positive consequence. I wrote this post on realizing that I can’t generate solar electricity on the roof of my house because of my tree. If we all chopped down all of our trees, and put in solar power, would that be better or not in the long term? That’s overly hypothetical, but at least with respect to my house, what does my community need more? A gorgeous huge oak or solar panels on my roof? I still don’t know the answer, if there is a good one.

  8. The ecosystem services you describe (“cleaner air, less surface runoff, slight drawdown of CO2, lessens urban heat island effect”) can all be supplied by lawns too🙂

  9. Without your Oak, your house would be 5-15 degrees hotter with the southern exposure. Given the amount of Sunny days in Pasadena, the majority of your energy use, not easily offset by solar panels is in air conditioning, which you would be using a lot of without that tree. This is based upon my take away from many discussions with my friend who happened to have designed software to calculate such things for both residental and commerial companies, as well as estimates for my own place. You do have options which can avoid the tree issue, but that’s a different comment….. But more to the issue, what about the phenomenon of people willingly spending more money for climate control and purposefully taking out large old trees that do not fit their aesthetic? This is not to gain covered living space, as often these lots have good square footage and the result is usually a concrete slab where the tree was….Here is a case where the money takes away trees….

  10. But lawns do all those things to a lesser extent on a per foot/meter of land area basis, right? Lawns/grass don’t take up nearly as much water as trees do. Trees ‘evapotransporate’ enough water that in the eastern US, the water table essentially only recharges in the winter.

    Maybe if people were managing their lawns to be prairie, then lawns might approach trees, but from what I’ve read (again mostly for eastern/upper midwestern US), trees far out punch lawns.

  11. Sure, in terms of the ecosystem services described above, trees out perform lawns. But lawns are (probably) better for delivering other services. The two that immediately spring to mind are production of floral resources to support wild pollinator populations (at least in the kinds of lawns I described in my blog) and as an integral part of sustainable urban drainage systems (SUDS). In addition there are situations where you just can’t/wouldn’t want to grow trees, e.g. very close to houses, on very shallow soils, on capped landfill sites.

    So I think the trees/lawns dichotomy is actually a straw man – I like both and both have their particular functions!

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