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Science

Urban Trees Grow Fast and Die Young (cosmosmagazine.com) 87

Trees in urban streets grow more quickly but die faster than those in rural forests, resulting in a net loss of carbon storage from city planting initiatives, new research shows. From a report: Researchers led by Ian Smith of Boston University, US, found that street trees in Boston grow nearly four times faster than those in forest stands nearby in rural Massachusetts. However, mortality rates of street trees are more than double those in rural forests, with young and very large trees most at risk. The findings have implications for urban greening programs, suggesting that planting initiatives alone are insufficient to meet municipal carbon storage, canopy cover and biomass goals. Many cities are embracing greening initiatives to improve urban sustainability and reduce the environmental impacts of urbanisation, the researchers write. "However, cities have been dramatically understudied by ecologists," they add. "Despite the widely espoused benefits of urban trees, the role of urban vegetation in the carbon cycle remains uncertain." Street trees take many years to pay their way on carbon costs.
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Urban Trees Grow Fast and Die Young

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  • quality of life (Score:5, Interesting)

    by Anonymous Coward on Thursday May 09, 2019 @11:54AM (#58564452)

    Can we stop measuring EVERYTHING in terms of how much carbon dioxide it produces or consumes. Having trees in a city make it a more pleasant living experience on its own. Also it often improves property values. Not everything needs to be justified in terms of atmospheric carbon dioxide.

    • by Smidge204 ( 605297 ) on Thursday May 09, 2019 @12:01PM (#58564494) Journal

      > Having trees in a city make it a more pleasant living experience on its own.

      Well, as long as they're not Bradford Pear trees I suppose...
      =Smidge=

    • by MobyDisk ( 75490 )

      There's no way urban trees are carbon sinks. They are grown in tree farms, shipped to the city, and their roots destroy the surrounding concrete.

      • If the trees are so packed in that they will damage concrete, then the city planner didn't plan very well. Sadly it's all built now so it will remain an ongoing issue, but its still better than no trees. I hope new cities and surrounding expansions are better planned.

        Groups of trees would probably be better than those soldiered along between roads and sidewalks.
    • Re:quality of life (Score:4, Interesting)

      by phantomfive ( 622387 ) on Thursday May 09, 2019 @02:13PM (#58565164) Journal

      Can we stop measuring EVERYTHING in terms of how much carbon dioxide it produces or consumes.

      Measuring it in terms of CO2 relates it to AGW and makes it easier to get funding.

      Study to measure how urban trees affect global warming? Funded.
      Study to measure how urban trees make you happy? Funding harder.

      A lot of scientists' work lives revolve around getting funding, so if you want to study trees in an urban environment, relating it to global warming makes it easier.

    • by denzacar ( 181829 ) on Thursday May 09, 2019 @04:00PM (#58565878) Journal

      Street trees take many years to pay their way on carbon costs.

      You know... to payback for all those years trees spend flying around the globe on jets while burning plastic for fun.
      Cause trees are assholes I guess.

      Trees are a fucking carbon sink from seed forward.
      They are made out of fucking carbon sucked from the air - that's why we can use them as fuel. All that carbon in them.
      Which they are NOT getting through their root system but through their leaves.

      So where does that "trees can't ever pay their way" bullshit come from? Well... this bit in the study:

      The carbon costs associated with nursery production, planting, irrigation, pruning, removal, and disposal are high [16]. Street trees must survive for several decades (26-33 years; [27]) to attain carbon neutrality.

      Oh really?
      Well then... let's see those studies.
      16. Kendall A, McPherson EG. A life cycle greenhouse gas inventory of a tree production system. Int K Life Cycle Assess. 2012;17:444-452. [fs.fed.us]

      One of California's largest tree nurseries was estimated to release 10,837 tons CO2e in 2009, or 4.6 and 15.3 kg for a typical #5 and #9 tree, respectively.
      This amount is relatively small compared with average annual CO2 uptake rates by established trees that ranged from 39 to 96 kg.

      Study didn't measure the CO2 sequestered by the trees as they grew to be "a typical #5 and #9 tree, respectively."
      Also, numbers listed are for "ornamental trees". Which is something never defined in the study, but the nursery used to gather the data [monrovia.com] offers everything from figs to you average pine.
      Needless to say, that "per tree" average may be more than a little off.
      Which is why they report numbers "more than 100 times higher than... seedling production for forestry operations".

      Production emissions for trees used in urban forestry are 4.6 and 15.3 kg for a typical #5 and #9 tree, respectively. These emissions are more than 100 times higher than those associated with seedling production for forestry operations, estimated at 0.029-0.133 kg per seedling (CORRIM Inc. 2004; Aldentun 2002). This result is not entirely surprising because ornamental trees used in urban forestry remain in the nursery much longer, on the order of 4 to 5 years.

      I.e. Even with numbers skewed by a lousy methodology and poorly defined sample - trees still suck up way more carbon than is used in their production.

      But what about that second study, the one claiming it takes decades for a tree to reclaim the CO2, actively rebutting the study above?
      Well... Cherry trees are trees too. And should you take a cherry picker to your local cherry tree you can pick any shit you feel like picking.

      27. Petri AC, Koeser AK, Lovell ST, Ingram D. How Green Are Trees?â"Using Life Cycle Assessment Methods to Asses Net Environmental Benefits. J Environ Hort. 2016;34(4):101â"110. [hrijournal.org]

      In a cradle-to-gate analysis, container nursery production of a #5 (nominally a 19-L or 5-gal) tree was found to be a net greenhouse gas (GHG) emitter, with an estimate of 4.6 kg (10.1 lb) of CO2e (Kendall and McPherson, 2012).

      Do note how it cites the study above as if it proves trees to be net polluters. Completely ignoring the very next line in the study.
      Naah man... trees... they like... pollute the air man.

      Similarly, study simply rounds up numbers to whatever is available. Thus it assumes that a 5-gallon tree weighs 136 kilograms and that every single tree is delivered one at a time.

      A delivery weight of 136 kg (300 lb) per tree was used to establish the ton-km for a SimaPro (Simapro, PRé North America, Inc.

    • Agreed, the focus on Carbon pollution mitigation as the main environmental concern has been a real disaster for environmental reporting. Smog, particulates and as you said, just general livability should have all taken the limelight but instead we are forced into talking about Global Warming - a topic that far too many people just dismiss.

      There is a great comic that has a professor talking about global warning and someone says from the crowd "But what if we try to fix it an we're wrong and all we do is m
    • by antdude ( 79039 )

      So fake trees are OK? :P

    • News at 11 - Any plant that is overfed nutrients is going to grow fast and die young. Scientists discover yet another easy to guess fact while spending your tax dollars. Thank you. That is all. Solution? Keep planting more trees, which the money for the study could have paid for.
  • California (Score:5, Interesting)

    by Anonymous Coward on Thursday May 09, 2019 @11:58AM (#58564470)

    San Fernando Valley trees were abandoned by the cities who cited drought as the reason they stopped watering. Even though all city land is watered with reclaimed water not suitable for drinking. This led to all the trees and vegetation dying. Which the city then dutifully dug up and replaced with new greenery and trees. Which they then didnt water. Etc.
    It seems the money to buy plants comes from s different bucket than the money to maintain them.

    • Re: California (Score:5, Informative)

      by squirreltactic ( 5943416 ) on Thursday May 09, 2019 @12:53PM (#58564754)
      I can't speak to how it's done in your municipality, but I can tell you how it works in mine. Tree planting ends up being cheaper than maintenance costs. While there is an overall budget for the urban forestry department, often tree plantings have matching dollars for every dollar spent. There are grants out there that will match dollars as well as private city beautification organizations that will also match. So in many instances, one city dollar spent on plantings turns into three. So it makes fiscal sense to focus on plantings. Also, we have something called a tree bank. When a business builds, it's required that that business plant a certain number of trees (both overstory and understory) on the right of way. That isn't always possible. For instance, the whole place is already concrete. They instead put money for the trees into the tree bank, which has to be used to plant trees by the city. So often it ends up with maintenance money spent on trees which pose a danger rather than ensuring trees survive it have good form.
  • by Anonymous Coward

    Older trees produce less oxygen and absorb less carbon dioxide than younger trees.
    So if trees die faster the average age of trees goes down and their oxygen producing and carbon sequestration are greater.

  • Plant more trees, not just Urban areas but everywhere we can.

    • Re:Simple (Score:4, Interesting)

      by bugs2squash ( 1132591 ) on Thursday May 09, 2019 @12:15PM (#58564572)
      I suspect that the research will find a species of tree that best meets the target criteria - long life, low maintenance, CO2 reduction etc. And then we'll see a monoculture of urban trees, every single one of them the same species.
      • Re: (Score:3, Insightful)

        Yep, and then some arboreal disease will come along and wipe them out in just a few years. Back to the drawing board!
      • And then we'll see a monoculture of urban trees, every single one of them the same species.

        It won't be a monoculture of one species; it'll be a monoculture of clones from the same individual tree, which is even worse.

  • by Kohath ( 38547 ) on Thursday May 09, 2019 @12:21PM (#58564588)

    If you're not a religious environmentalist, your urban trees don't have to pass tests for climate virtue. You can just enjoy having them for their appearance and for the shade they cast.

    Consider just enjoying things that make life better, like neighborhood trees, instead of worrying about passing someone's purity test.

  • by Solandri ( 704621 ) on Thursday May 09, 2019 @12:24PM (#58564606)
    So plant trees in urban areas, and when they die you cart them off to a landfill and bury them. Don't try to compost them - that just releases the carbon back into the atmosphere. Burying them in a landfill sequesters the carbon back underground. And since the urban trees grow 4x faster (probably due to the regular watering), that means it's 4x more effective at sequestering carbon than if you buried trees which fell in a forest.
    • by JBMcB ( 73720 )

      Don't try to compost them - that just releases the carbon back into the atmosphere.

      Most large-scale composting is anaerobic, meaning the bacteria and microorganisms that live on the rotting vegetable matter do not use oxygen or release much carbon dioxide as part of their metabolism. That's where you throw everything in a big pile and let it rot, which is how most municipal composting programs are done (think giant piles of leaves or leaf bags.) Aerobic composting is much faster but more difficult as you have to turn everything frequently.

      Some CO2 does escape, and some methane is produced

      • Some CO2 does escape, and some methane is produced, but the majority of it is kept in the decayed vegetable matter.

        Bury it for long enough with enough pressure and heat and future generations millions of years from now will have a convenient energy source. It's kind of a polluter though.

        All of the fossil fuels that we have now are really just million year old compost heaps. If the process didn't work the way you describe, we wouldn't have this problem to begin with, but we'd probably have something else to take its place.

        I think that in the future we'll actively start growing certain types of plants with the inten

    • I don't know but I'd be curious if faster growing/dying also due to:

      1. More sunlight availability
      2. Improper care by the city
      3. Fertilization
      4. Species picked (Can't find it in the article that compares apples to apples, err apple trees to apple trees)

    • They probably grow faster cause higher CO2 ppm, regular watering and more direct sun onto each individual tree.

    • My first thought was to make something with them. If they're growing 4x faster, and are yielding a useful material, that's a huge gain, and you might find companies willing to harvest/replant.

      • Generally sawmills want nothing to do with residential or city trees, too many nails and other junk wind up buried in the wood and wreaks havoc on blades and equipment. It pretty much winds up as firewood or mulch.
    • "since the urban trees grow 4x faster (probably due to the regular watering),"

      My hunch is that they grow faster because of less competition for light from neighboring trees. A solitary tree grows in a verdy different shape (ball-like) than a forest tree (most leaves near the top).

    • Depends how much fuel you have to burn to cut down and transport the trees. That's a lot of weight, and tricky if you transport it as a solid log without chipping it first (and chipping it would make it break down faster, so it doesn't sequester as much).
    • by epine ( 68316 )

      Burying them in a landfill sequesters the carbon back underground.

      Yes, and it also sequesters all of the other nutrients which a tree contains.

      The ecosystem of Pacific temperate rain forests is so productive that the biomass on the best sites is at least four times greater than that of any comparable area in the tropics.

      In sheer mass of living and decaying material — trees, mosses, shrubs, and soil — these forests are more massive than any other ecosystem on the planet.

      In part, this is due to th

  • it isn't easy being green.

    I mean with all the street tree gangs fighting it out for sunlight, territory and providing local shade.

    The Oaks and the Maples are still under Homeland Security investigation regarding their actions against the Palms and the Dogwoods. /s

  • I'm guessing the more trees you plant in the urban area, the less this holds true.
  • by duke_cheetah2003 ( 862933 ) on Thursday May 09, 2019 @01:10PM (#58564832) Homepage

    Let's look at these two statements:

    trees in Boston grow nearly four times faster than those in forest stands nearby in rural Massachusetts

    Seems legit. Ok, then this:

    suggesting that planting initiatives alone are insufficient to meet municipal carbon storage

    Right. Stay with me. Now.. if the trees grow four times faster, sucking that much more CO2 out of the atmo at a faster pace......... see reality breaking suddenly?

    • Actually, recent research into jet fuel biomass shows that you can get lots from planting young trees as hedges between farm plots, cutting them down to the trunk every 2-3 years, and the resulting spinnies of young growth makes excellent biomass to generate jet fuel out of.

      (source: UW and WSU biofuel and agricultural research)

  • Or in other words, life's a Beech, and then you die....

  • Seems to me that carbon sequesteration by trees, especially in an urban environment, is a crock.

    Urban tree material, leaf, root and branch, isn't going to be buried for geologic time. Fallen leaves or needles will be into the soil and back in circulation annually. Wood will be cut down and/or dug up and disposed of once the tree is trimmed, dies, or in the next cycle of urban prettification. What percentage of that is going into geologic strata? What percentage is trapped in the soil, and for how long?

    So most of the carbon is just out of circulation for periods of months, a year, or perhaps some decades, then gets back into the carbon cycle, which means back into the atmosphere. For the multiple century timescales of the global warming flap, you only get to count the tiny fraction that ends up actually removed from the game, not the vast bulk that just takes a short vacation.

    (If you keep replacing the trees as fast as they die, so your project increased the biomass of living trees, and urban planners maintain that increase at least until the fall of urban civilization, you do get to count the increase, but only once.)

    Not only that, but most of the carbon that returns to the atmosphere by anaerobic decay below the water table does so, not as carbon dioxide, but as methane. Those molecules hang around for an average of about twelve years before oxidizing to carbon dioxide and water. But for those twelve years that carbon is about 86 times as effective [scientificamerican.com] a greenhouse gas as carbon dioxide. So the tree has to trap that carbon for something over a THOUSAND YEARS to reach break-even.

    How much of the carbon ends up burned back to CO2 on disposal? How much rots back to CO2 above the water table (and how long does that take?). What tiny fraction ends up sealed under rock for millenia?

    • Over time, in a forest the soil level grows deeper and deeper.
      • by PPH ( 736903 )

        No. Take a walk in an old growth forest with a shovel and see how quickly you can dig through the biologic layer.

  • Live fast, have fun and die young. Worked for James Dean. https://www.latimes.com/local/... [latimes.com]
  • by mschaffer ( 97223 ) on Thursday May 09, 2019 @02:42PM (#58565400)

    Urban trees are poorer. They often pay higher taxes and rent as well as make little income. Also, due to poor social infrastructure, these trees often succumb to alcoholism and drug abuse at an early age. All of this factor conspire to prematurely age the tree and shorten its life expectancy.

  • I can't tell you how irritating these urban trees are. They live fast, die young, drop branches on dogs peeing on them, wear strange clothes like light strings and alligator skins, and have loud music.

    Why can't they behave?

  • The study does not compare like with like in many characteristics, and hence is pretty much meaningless. Tree growth slows as they age, so they needed to ensure their samples were comparable in age. Tree growth varies by species, so since they chose a forest dominated by native trees they needed to measure only trees of the same species planted on the streets. I could go on ... why measure biomass growth of individual trees rather than per land area. Crowded forest trees will each get a limited amount of li

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