Urban trees 'live fast, die young' compared to those in rural forests | Hacker News Reader

Urban trees 'live fast, die young' compared to those in rural forests

phys.org

183 pointsdnetesn109 comments

I highly recommend reading the book "The Hidden Life Of Trees" by Peter Wohlleben

There is an informative chapter/section called Street Kids about trees planted along the streets primarily in urban areas. How their health is impacted by having no network of close cousins nearby to communicate/ suppy nutrients via root/fungi, etc.

https://www.amazon.com/Hidden-Life-Trees-Illustrated/dp/1771...

Came here to discuss the same section. It makes sense that urban trees die younger when you think about how heavily the odds are stacked against them:

* No network of fellow of trees to share nutrients and information with via their roots, as mentioned above.

* Dogs constantly pissing on the trunk.

* Smog.

* Planted in a small patch of dirt, surrounded by concrete. The dirt itself is usually extremely compacted so no water gets through to the roots.

* Gardeners and city workers constantly cutting off branches, exposing inner wood to deadly fungi.

I thought the piss was nutritious for plants?

Not so much on their trunks.

As with many things, the quantity matters. Too much of a good thing is not beneficial. If you over fertilize, it can "burn" the plant. That is why most dog owners will find dead spots in their grass where the dog prefers to pee.

Not to mention people constantly ramming vehicles into them. There's not a tree in my town that doesn't have a big scar on the trunk at bumper level.

Not a single one?

Not even the one in their backyard.

You got me. I exaggerated. A large number of streetside trees in the downtown area have accident scars on them.

It's a town tradition to inaugurate a tree's planting by ramming it with a car.

the odds are not stacked against them, plants (and other living creatures) do their best to colonize new places. That's why trees have soooo many seeds. Reproduction is the goal, not longevity.

Do you see a lot of urban trees naturally propagating?

Living in an urban forest, ripping up wild young trees is part of normal yard maintenance. I probably get at least a dozen a year. Two of my full-sized trees in my yard were wild seedlings that I allowed to grow because I like those particular kinds of trees (a catalpa and a sumac), and they were in good locations.

This also includes invasive tree species like buckthorn, which is a villain in our area. Buckthorns pop up constantly.

I guess one could view urban tree dynamics as extreme selection for certain traits. They have to be pretty, and in a location that won't inconvenience humans, and they can't do anything to inconvenience humans, like cause allergies, and they have to be extremely resilient.

And around here, they have to be ok if it hits -20F sometimes in the winter.

I have a magnolia, and it completely boggles me that it survives and thrives this far north.

There are also some advantages. Urban trees, being more spread out, sometimes have greater sunlight and therefore grow faster. For some trees age isn't the limiting factor but height. They grow until they risk toppling over.

So the urban tree does die "young", but is the goal to keep trees alive as long as possible? If it is, then there are lots of things that can be done to slow their growth and prolong their lives. Deprive them of nutrients. Shorten their growing season. Keep them cold. Some of the oldest trees live in the most extreme environments. Bonzi trees age very slowly too. Perhaps we should trim our urban trees more aggressively.

https://en.wikipedia.org/wiki/Methuselah_(tree) (5000+ years old, 10,000 feet above sea level)

>but is the goal to keep trees alive as long as possible?

For some trees, being 100year old means that the trees are in their late teens/twenties/thirties (source above book). With that in mind, the answer to above question becomes somewhat difficult.

For many cities, the goal is a healthy and sustainable urban canopy. Arboriculture has advanced a lot in the last hundred years, and we've made a lot of mistakes.

Eg, inappropriate species like Big Leaf Maple in inappropriate locations, like under power lines. Bad pruning practices. Planting monocultures (Elm). Boxing in roots.

As sick trees come down, better practices can lead to better trees for the next generation.

For some common species, 100 years is downright old, and reaching the end of their natural life anyways.

You are also applying mammalian standards to a plant. Trees may indeed be capable of living a very long while, but that does not mean that such lives are normal. A tree can live a full and productive life, reproducing and spreading many times, centuries before its total lifespan. There is also some speculation that trees may be immortal, that if their growth is artificially managed that they may just never have to die. Plants are different than mammals. They don't all have the same definitive life cycles.

> is the goal to keep trees alive as long as possible?

climate change and economic reasons would support this goal.

> Perhaps we should trim our urban trees more aggressively.

Killing it much faster

10k above sea level would also put the tree well above major jet streams that carry pollution. A similar pattern occurred with a group in (I think) Norway, that were said to have the "fountain of youth", but it just simply turned out they were out of the way of pollution.

Sorry to nitpick, but I think you might have confused 10k feet vs 10k meters (10kms). The grandparent was using feet. 10k feet is about 3kms, the height of a medium sized mountain. 10kms is about the height of Everest, whose peak does not have trees at all. I don't know at what elevation trees stop appearing, but it would be well under 10kms.

> I don't know at what elevation trees stop appearing

This is known as the "tree line", and varies a lot based on particular location (due to sun exposure, climate, and plant species). Here's a wikipedia article which outlines where the tree line: https://en.wikipedia.org/wiki/Tree_line . Summary is that the treeline is rarely above 12k feet (3500m), though in Bolivia it gets all the way up to 17k feet (5200m)!!

You are probably correct w.r.t. the main flow of the jet stream being far in excess of the highest tree lines in the world. The jet stream's main flow is usually 30k feet (10k meters) or higher.

The canonical paper on this topic is Edmund Schulman's classic "Longevity under Adversity in Conifers" (1954)[1]

When I worked in a tree-ring dating lab, we always sought out the harshest local environments in a region and then at a given site, the harshest micro-environments (typically water limited but fire protected) because that's where you find the most ragged, pathetic, and correlatively oldest trees around with the most climate sensitivity in their ring patterns. This makes the ideal trees to date and build climate chronologies from.

[1]: https://sci-hub.tw/10.2307/1682970

> So the urban tree does die "young", but is the goal to keep trees alive as long as possible?

In an urban area, it should be. Not only does it cost money to have to replace a dead tree, but a dead (or even not-quite-yet-dead) tree runs the risk of falling over, which means damaging property, blocking streets/sidewalks, or even injuring/killing animals (including humans).

The "close cousins" thing is interesting for me. I live in a tree-lined streets neighborhood. Historically, they chose species on a street-by-street basis. My street was all linden trees for the curb trees (except for a last remaining elm, we've lost most of them to Dutch Elm disease). A few years back, a severe wind storm took out seven of the curb trees on my block, in a cluster (and smashed a few cars in the process).

Rather than planting more lindens, the city put in a diverse new collection - I think every one is different. Our new tree is a hackberry. Our next door neighbor got a japanese maple, and there's a buckeye across the street, etc.

So now I'm wondering what that means for the long-term health of our scrawny little hackberry. I don't know of any other hackberry trees in the neighborhood - the dominant species are lindens, maples, walnuts, ashes, catalpas, and a few ancient elms. Within our yard, there's a big old ash, a catalpa, a sumac, a magnolia, and a dogwood.

Oh, and I live in an urban forest, apparently.

I don't know about your hackberry in particular. This has been a topic of fascination for me, though.

Trees connect to each other via symbiotic root fungi called "mycorrhizae". Any given species of plant probably has several species of fungus with which it is compatible. The fungus and the plant form a mutually beneficial pair, but the fungus can additionally connect to other nearby plants. Then you have a network, potentially with multiple plant species.

The network can be used for nutrient storage (summer to winter), nutrient transfer (to offspring), or chemical signalling. ("Bugs attacking. Get ready.") Different species are known to support each other, giving nutrients back and forth and different times of year. Of course, the black walnut will use the network to poison its neighbors.

Playing in my flower pots, I have observed that plants growing right next to sweet potatoes or succulents do better when I forget to water them, but I haven't measured that. In my mind, they're leaching water from their neighbors through the network.

So, it's complicated, and there is such a thing as a bad actor on the network, but basically I don't think your tree will be lonely. I'm optimistic.

Roots of the same species can fuse directly. It helps canopy tree species grow up inside of an already closed canopy, and similar to mycorrhizal networks, can spread around sugars and water.

Hackberrys grow very quickly, you can water them and watch it grow like a weed. They also fall down in storms. I removed one from my yard and will be planting an Eastern Persimmon instead.

Mine still looks pretty sad and despondent after a couple of years. I hope it's beautiful someday, but for now it's pretty dull next to its glamorous Japanese maple neighbor.

Well, check on soil quality, maybe add compost, check water supply, maybe add a dripper, check that the soil isn't rock-hard, so the roots can get around. If you want to know exactly what the tree needs, though, research is probably in order.

OK, here's a pretty thorough guide to the hackberry: https://homeguides.sfgate.com/special-care-hackberry-tree-56...

Sounds like you should keep crap off the trunk so it doesn't rot, it needs to be pruned to grow right, and if the soil gets dry it will start dropping leaves about it.

An article posted here recently (https://blogs.scientificamerican.com/guest-blog/botanical-se...) stating that urban trees are also predominantly male (fruitless), which is causing a rise in air pollen levels.

I think a bigger issue is healthy trees being cut in a lot of urban areas.

https://www.dailymail.co.uk/news/article-5801627/Great-tree-...

Reference to UK, but I can see the same happening in Ireland and Portugal.

I think a lot of trees were cut down in Portugal due to allergy concerns, despite that being mostly a misconception of the causes, but I can't say I've noticed an actual reduction in the number.

Happening in Paris as well: the city keeps cutting trees that are more than 100 years old just because they can:

http://www.leparisien.fr/paris-75/paris-la-place-de-la-natio...

Article says that they took down the trees in order to undertake a study on how leak-proof the subway lines beneath the trees were? There's got to be a better way.

That's just the excuse they needed.

Frequently, the first step when building in the US is to rip down any existing trees and completely clear the property

This is likely regional dependent. In Alaska and Western Washington this is definitely true. When my neighbor built his house they tore down the forest.

In Utah tho where trees are harder to grow and establish, the construction company will often ask you, or just leave mature trees where they are as long as they aren't blocking the house.

Yeah there definitely need to be local restrictions on this when trees are more sparse. Atlanta requires approval and paying a fee to cut down trees on a lot, but some argue the cost is still too low to discourage it.

They recently did that in my area (rural/suburbs in Canada).

They cleared a huge section of old-growth forest to make a big community area covered with grass.

Instead of keeping some trees aside or not clearing the whole thing, they planted new young sapling all around the pedestrian paths and bicycle lanes.

Everyone is complaining about the lack of shade in that area (so big it feels like you are standing in the middle of a plain) and the city's answer is: "Sorry, we planted trees but they won't be big enough to cast shade for years. Just be patient."

It feels ridiculous because the whole area is surrounded by forest.

And then the trees will grow with the branches overhanging streets, powerlines, and homes - prompting the city/power utility to trim them. But naturally they won't hire arborists to do it.

The city of LA did that in my neighborhood last year. My street might as well have no trees at all.

It's kind of sad. Reminds me of the (several) cartoons I saw as a kid where the bulldozers come and conquer the forest.

That article specifically says they’re not “healthy” per se:

> Thousands of trees in the city, assessed by the contractor Amey as dying, diseased or dangerous, have been axed.

Sometimes, that's due to blights. We're losing a lot of beautiful, mature ash trees to emerald ash borers. So any tree with even a hint of them leads to immediate destruction.

I have a big, beautiful ash tree, and live a few blocks from a large park (a couple of square miles) with hundreds of ash trees, so I worry just how long I'll get to keep my tree.

I wonder if urban trees will adapt to city life - but I guess it depends on where the cities get their new trees. If it's not from the city's tree gene pool we will put forest trees into cities and they won't far any better 200 years from now.

I think it will also involve selecting seeds only from "better" performing trees from the city tree gene pool. This will then ensure that beneficial mutations / changes survive. An unfortunate requirement of evolution to force progress.

In a way it will be survival of the fittest for trees. Unfortunately it might take considerable work from urban planners which I cannot see happening on a large scale any time soon.

Maybe a better idea will be to selectively breed species in hard environments and then distribute the seeds to cities that need them. With genetic modifications becoming prevalent in the food industry this might be not far away from happening.

>I think it will also involve selecting seeds only from "better" performing trees from the city tree gene pool. This will then ensure that beneficial mutations / changes survive. An unfortunate requirement of evolution to force progress.

>In a way it will be survival of the fittest for trees. Unfortunately it might take considerable work from urban planners which I cannot see happening on a large scale any time soon.

I greatly look forward to Cambridge trees that wake up at 10am toke it up 'til noon and complain about life being hard, New Bedford trees that pack heat, Boston trees that think they're the center of the universe and other environment specific adaptations.

> In a way it will be survival of the fittest for trees.

What if the "fittest" trees end up being the ugliest or most allergy-triggering?

My point is if its run by humans, it probably won't really be survival of the "fittest".

If it's run by humans, then human decision becomes part of the selection, shaping what "fit" means.

The idea that we would use random natural selection for urban trees feels archaic. We don't use natural selection for our crops or livestock or much of anything any more.

Urban trees will almost assuredly, like all of the other lifeforms we grow and rely on, be altered through human selection (be it simple old techniques like cross breeding, or advanced techniques like genetic modification)

i.e. https://en.wikipedia.org/wiki/Genetically_modified_tree

They already are. Most trees at the nursery are carefully cultivated strains, and many are clones.

I will admit it's handy when planting on my eighth acre to know ahead of time how big a tree will get, for example.

This already happened long ago by artificial selection and hybridization. One example that is found all over the world in Urban areas is the highly pollution resistant London Planetree:

https://arbordayblog.org/treeoftheweek/london-planetree-toug...

Only problem is that at least in my area, they constantly shed leaves, all season long.

The London plane tree, a hybrid between the eastern sycamore and the american sycamore, could be an example of this. They were some of the only trees that could cope with the heavy pollution in London during the industrial revolution. Here's more information if anyone's interested: https://londonist.com/2015/03/the-secret-history-of-the-lond...

EDIT: Looks like someone also mentioned the london plane before me

If you want to read the full study: https://journals.plos.org/plosone/article?id=10.1371/journal...

> The role of street trees in the urban carbon cycle is complex as the environmental costs and benefits of street trees evolve over the course of a tree’s life, with emissions associated with establishment often precluding net greenhouse gas benefits in the early stages of a street tree’s life cycle. The carbon costs associated with nursery production, planting, irrigation, pruning, removal, and disposal are high. Street trees must survive for several decades (26–33 years) to attain carbon neutrality.

That's much longer than I would have expected.

That's the urban lifestyle in general, isn't it?

Nope.

> Life expectancy was inversely related to levels of rurality. In 2005-2009, those in large metropolitan areas had a life expectancy of 79.1 years, compared with 76.9 years in small urban towns and 76.7 years in rural areas. When stratified by gender, race, and income, life expectancy ranged from 67.7 years among poor black men in nonmetropolitan areas to 89.6 among poor Asian/Pacific Islander women in metropolitan areas. Rural-urban disparities widened over time. In 1969-1971, life expectancy was 0.4 years longer in metropolitan than in nonmetropolitan areas (70.9 vs 70.5 years). By 2005-2009, the life expectancy difference had increased to 2.0 years (78.8 vs 76.8 years). The rural poor and rural blacks currently experience survival probabilities that urban rich and urban whites enjoyed 4 decades earlier. Causes of death contributing most to the increasing rural-urban disparity and lower life expectancy in rural areas include heart disease, unintentional injuries, COPD, lung cancer, stroke, suicide, and diabetes.

https://www.ncbi.nlm.nih.gov/pubmed/24439358

Very, very confounded correlations study. Given the greater prevalence of schizophrenia in urban dwellers and the negative effects of air pollution we have pretty strong reasons to suspect urban living is less healthy than rural living. But in a modern economy the highly educated and high socioeconomic status people who are disproportionately healthy will almost all live in urban areas.

Correlational studies are only ever suggestive.

All of these are due to behaviour, not environment.

> Causes of death contributing most to the increasing rural-urban disparity and lower life expectancy in rural areas include heart disease

Diet

> unintentional injuries

Working on a farm is ludicrously dangerous

> COPD, lung cancer

Rural people are poorer and poorer people smoke nope

> stroke

Diet

> suicide

Comparatively easy access to guns and poisons

> and diabetes

Diet

Is this a joke? Life expectancy has been increasing as people left the countryside for the cities. It's not even a matter of debate.

It's only relatively recently that cities began to have higher life expectancies than the countryside. Last 200 years or so, IIRC.

That's not at all what the original comment ' That's the urban lifestyle in general, isn't it? ' was suggesting.

>>> Life expectancy has been increasing as people left the countryside for the cities.

It's a comment on the causation here - if 'moving to cities' caused an increase in life expectancy in general you'd expect people living in cities to always have higher life expectancy than people in the countryside, and that's what my comment was refuting. Instead, it seems that life expectancy has been rising at the same time as people have been moving to cities, but moving to cities is not what caused the general life expectancy changes.

EDIT: Also, people have been moving to cities for millenia, it's just only been the past few centuries where those cities stopped being massive deathtraps and thus actually started growing.

Moving to current cities may still be what's causing life expectancy to increase, even if moving to cities in the past didn't. Cities weren't held constant.

Of course! But I'd still guess that it's not some intrinsic property of cities, and that a large part of the difference would be explained by income differentials (or job differences - no chance of getting crushed by a tractor in Times Square).

If job differences are not intrinsic to cities, what is?

Density, maybe?

Yeah, and I'd say those differences in density inevitably cause differences in types of jobs. It's second order, but still intrinsic.

These days it is but back before the revolutions in public health at the turn of the 20th century cities were very unhealthy, so much so that they tended to be net consumers of population from the countryside even when they weren't growing.

Don't forget unions. We like to bag on them but factories with locked doors burning down with the people still inside gave the unions the teeth they needed to get things like that made illegal.

Haven’t read the full study but I’m curious to see how much diversity is factored in. In a lot of cities you see monocultures of the same “signature” tree — which often leads to disease.

My instinct would be to focus on mixing things up, and making sure there’s a wide diversity of trees; not just overall, but co-planting so there’s trees mixed with shrubs, grasses, wildflowers, etc. Mimicking the multiple vertical layers of a forest also maximizes photosynthesis so you get more carbon storage per meter.

Some do remarkably well in Washington, DC, given that they are planted between sidewalk and curb. They don't get much salt, compared to what they would in some northern states, there is that.

DC (the cities and suburbs around it even more so) has a massive amount of space between sidewalk and curb compared to older east coast cities that weren't planned.

Really? I'd guess that in my neighborhood it's around three feet, certainly not four.

I'll repost a comment I made a few years ago:

https://news.ycombinator.com/item?id=14156934

> I know a few arborists. This is generally the cycle:

> 1. There is a tree problem.

> 2. Muni orders some sort of study after the problem has become unassailable.

> 3. Arborist performs a study, finds lack of naturalized species, lack of diversity, lack of appropriately spaced trees.

> 4. Muni throws their hands up in the air because money and keeps doing the wrong things.

In my city the DPW constantly drops a sapling in a sidewalk cut out with no after care or follow up so they just die within a year or two. It seems like a real waste.

I’ve always wondered what would happen if instead they really prepared the soil and waited to see what trees naturally sprouted, then removed all but the healthiest looking one.

I wonder if my house plants are suffering socio-chemical isolation by being potted solo...

Probably as consequence of a mix among election of small species for small spaces,

contamination,

jailed roots

and the social pressure to constant prune and mow until killing the tree.

Good luck trying to find a sanctuary protected in the next 400 years for a fully fledged oak in the middle of a city.

Hard to expect anything different. The amount of salt that they get exposed to is horrifying, at least in places that experience cold temperatures and go nuts with the calcium chloride to melt off every speck of snow and ice.

Between the salt and the dog urine, hard to believe they survive at all.

Urine is just an aqueous solution containing urea (CH4N2O) and you need nitrogen in the ground since it is absorbed by plants and trees as nitrates. Nitrates are usually lacking in the ground so it's actually beneficial for the trees in the end.

https://www.fredericknewspost.com/news/environment/the-nitro...

Nearly all the trees and bushes on my street need barriers around them. The ones that don't will get peed on so much that the plant dies (or all greenery below a certain height will chemically burn).

Trees benefit from being around other trees, for example by passing nutrients through their root systems, signalling chemically to warn of threats, sharing beneficial fungi, and being shielded from the elements. It's definitely no surprise that urban trees don't fare as well.

There are some benefits for street trees that the article points out, including less competition for light, more CO2, more nitrogen deposition, a longer growing season, and the opportunity to tap water/sewer lines.

> the opportunity to tap water/sewer lines

Does this involve breaking pipes? How exactly is it beneficial?

It's beneficial to the tree.

Until they do it too much and get cut down for it, anyway.

A majority of instances won't involve breaking a line, although that certainly does happen. The typical case is that they'll thrive off of damp soil around pipes with small existing leaks and leach off that for hydration.

But wouldn't that be good for carbon capture? Let the tree grow quickly, then when it dies store the wood somewhere and plant a new one.

Store the wood somewhere? Am I naive to think that it will be burned?

Even burning isn't necessarily bad. Wood burned in nature (which we can simulate easily) will leave a lot of unburned carbon behind in the form of charcoal.

You have to deal with the air pollution though (which is a real problem, but been going on for longer than humans).

More light, more CO2, more pollution. Makes sense that cities could encourage faster growth and death.

So do the people. It's the only way to be.

are there any dense urban areas designed to coexist with healthy forests?

Arguably Atlanta, GA: https://en.wikipedia.org/wiki/Atlanta_tree_canopy

Live fast, die young, and leave a good looking copse.

Have your upvote and get out ;)

Wow. Best joke I've seen this week at least

It is also a very old one.

Did you read 'copse' as 'corpse', or is this really a common joke?

I did. I am not a native language speaker, so I did not notice the difference.

The original version is old, but I've never seen the pun with "copse"

Civilization is an affront to nature -- it's amazing how few of us understand this.

Civilization is nature.

Okay. Look at it structurally: is it Organic or Inorganic?

I love the debate about what is or is not "nature" these days.

We try to separate humans from other organisms because our use of tools/building nests is so far advanced from say, what an ant produces, or a bird making a nest, or a monkey with a stick.

But we're no different from those organisms in terms of tools and nesting, we're just really good at what we do. You could argue humans are different in that we possess self-awareness but that's an entirely different debate.

And then there's the "but what about our effect on the planet?" debate. What about it? Some say the effect we have isn't natural. But even that only has weight depending on what you mean by "natural". It's natural for humans to terraform and move earth the way we see fit. At the moment we're at risk of going extinct because of it, but the jury isn't out that we won't use technology to once again survive.

Look at the structural difference between systems of Nature and systems of Civilization.

And yet here you are, sitting in a building supplied by endless electricity, on an electronic device that takes an absolutely insane supply chain to produce, connected to mankind's greatest invention (the Internet), posting on a website that celebrates the most high-tech and capitalist goals imaginable.

All while railing against a civilization that is completely possible to exclude yourself from. Being here, making this comment, explicitly puts you, by choice, into "civilization".

I am not anti-civilization. I am presenting an objective framework. There is: organic ( Nature ) and inorganic ( Civilization )

Not sure how your comment relates...

Reply on news.ycombinator.com