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US Cities Lose Tree Cover Just When They Need It Most (scientificamerican.com) 135

An anonymous reader shares a report: Scientific evidence that trees and green spaces are crucial to the well-being of people in urban areas has multiplied in recent decades. Conveniently, these findings have emerged just as Americans, already among the most urbanized people in the world, are increasingly choosing to live in cities. The problem -- partly as a result of that choice -- is that urban tree cover is now steadily declining across the U.S.

A study in the May issue of Urban Forestry & Urban Greening reports metropolitan areas are experiencing a net loss of about 36 million trees nationwide every year. That amounts to about 175,000 acres of tree cover, most of it in central city and suburban areas but also on the exurban fringes. This reduction, says lead author David Nowak of the U.S. Forest Service (USFS), translates into an annual loss of about $96 million in benefits -- based, he says, on "only a few of the benefits that we know about." The economic calculation involves several such benefits that are relatively easy to express in dollar terms -- the capacity of trees to remove air pollution, sequester carbon, conserve energy by shading buildings and reduce power plant emissions.

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US Cities Lose Tree Cover Just When They Need It Most

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  • Compensating (Score:5, Interesting)

    by zmaragdus ( 1686342 ) on Monday May 07, 2018 @05:24PM (#56569856)
    With the emerging (but still very small) movement to add a lot of plants to the roofs / sides of buildings, I would like to see a study making a quantitative evaluation as to how much said plants can compensate for the loss of trees.
    • Re:Compensating (Score:5, Insightful)

      by drinkypoo ( 153816 ) <martin.espinoza@gmail.com> on Monday May 07, 2018 @06:38PM (#56570276) Homepage Journal

      With the emerging (but still very small) movement to add a lot of plants to the roofs / sides of buildings, I would like to see a study making a quantitative evaluation as to how much said plants can compensate for the loss of trees.

      I don't know, but I can take a semi-educated guess. Old forests with mature trees typically (that is, for almost all species) sequester more carbon than young ones which are still growing. It seems counterintuitive, but the key is that old forests have substantially more biomass — the trees have to respirate in order to maintain it, and it's their respiration which is the basis of most of the benefits of trees. Therefore, the benefits will essentially scale with the biomass, which is to say that trees are more beneficial.

      Some of the benefits of trees are irrespective of their biomass, for example their effect on albedo. This can as easily be produced by leafy salad greens as a redwood tree. But carbon sequestration, air filtration, and regulation of humidity (just off the top) are all linked to biomass.

      • Old forests with mature trees typically (that is, for almost all species) sequester more carbon than young ones which are still growing.
        Is that supposed to be a joke?

        Obviously it is the opposite around, growing trees convert CO2 into wood ... grown out trees only "breath" to stay alive.

        • Old forests with mature trees typically (that is, for almost all species) sequester more carbon than young ones which are still growing.

          Is that supposed to be a joke?
          Obviously it is the opposite around, growing trees convert CO2 into wood ... grown out trees only "breath" to stay alive.

          The time before last (approximately) that this came up, I did the research, looked it up, and provided a citation that proved my point. I'm not going to do your homework for you here, because I've already done it and posted the results here on Slashdot (with links). It is a fact that for the vast majority of tree species, mature forests sequester more carbon than new growth. Go forth and prove me wrong if you think you can. I'll check back. But this is why using trees for carbon sequestration, while still a

          • Sorry, Drinkingpoo.

            A grown up tree sequesters absolutely nothing.
            The CO2 it "eats" is going during spring into its new leaves. Then into its fruits.
            And in autumn it drops the leaves, they rot, and create the exact same amount of CO2 it costed to grow them. The fruits rot or get eaten and in the end result in the same CO2 that was used to grow them.

            If you believe other wise, you have a bad education (e.g. law of conversation of energy)

            Where actually would the "sequestered CO2" go to?

            • Re:Compensating (Score:5, Informative)

              by Tool Man ( 9826 ) on Monday May 07, 2018 @10:39PM (#56571202)

              You know those colored bands, known as "rings", in wood? The ones that are created anew year after year? What do you think they're made of?

              Now, consider that they'll often be roughly the same thickness on average each year. Each circle is larger than the one before, so it's layering on more circumference all the time. As long as the tree is still alive, it's adding more to the trunk alone.

              I'll allow that some trees die fairly soon in human terms, but many do not. Still though, even alders or poplars are bigger each year for their relatively short, fast-growing lifespan.

              • Yes, they get thicker.
                Hence they build wood, hence they take in CO2.

                However: is that relevant considering how few very old trees we have and how many young strong growing trees we have?

                • by Tool Man ( 9826 )

                  I suspect that the overall carbon sink effect will be the combination of two factors:
                  1. First, you have the overall mass that is converted from atmospheric CO2 into cellulose.
                  2. Second, there is the time duration for which that mass remains in solid form, so not converted into CO2 or methane.

                  The result then, is something like mass x time, where the mass is proportional to the volume of wood.

                  Young trees are dramatically smaller mass; even if they get tall quickly, they'll still

                  • Add to that the facts that plants are made almost entirely out of carbon, and that virtually all carbon even heavy soil carbon users like corn are made from comes from the atmosphere, and you've got more or less the whole picture. Even in a forest fire, not all of the carbon the trees are made of is released into the atmosphere. Some of it becomes charcoal, falls over sooner or later, gets buried by duff and is sequestered as biochar. Some of it becomes soot, most of which also goes into the soil (or into r

                    • by Tool Man ( 9826 )

                      Excellent info, thanks!

                      I've liked this saying I heard a while back:
                              “The best time to plant a tree was 20 years ago. The second best time is now.” – Chinese Proverb

                      While my fairly rural yard is only about 1/3 cleared, I have planted a few (more) fruit trees this spring. They'll never be huge, but will provide more shade, shelter and tasty food. I have no plans to cut fir and hemlock that takes up much of the rest.

            • Where actually would the "sequestered CO2" go to?

              Branching and branch and tree girth. Also, root system to support all that. Trees grow in three dimensions.

              • Focusing on individual trees is the hard way to approach the problem. If you think about the ecosystem as a whole then it is pretty obvious that mature forests are carbon neutral. Sure there is new growth but that is offset by dead old growth decomposing. The biomass of the ecosystem remains about the same.

                Of course that doesn't mean that old forests are unimportant. If you completely burn an old forest, nearly all that locked-up carbon becomes carbon dioxide.

                • Focusing on individual trees is the hard way to approach the problem. If you think about the ecosystem as a whole then it is pretty obvious that mature forests are carbon neutral. Sure there is new growth but that is offset by dead old growth decomposing. The biomass of the ecosystem remains about the same.

                  Also wrong. Only jungle rainforests are around the break-even point, because of the rate of decomposition. Aerobic decomposition releases less sequestered CO2; more of the carbon is left in the soil. The less-rapid rate of dieoff in other kinds of forest (including redwood forest, which is a rainforest) means that decomposition can happen aerobically, because it doesn't create such deep duff. Even rainforests sink carbon, just not very much; their primary purpose is to filter.

                  • Nitpicking again?

                    Who the funk cares if a forrest is 100% carbon neutral or 99.5%?

                    The idea that a forrest, a grown one, sequesters carbon is just bullshit.

                    Even rainforests sink carbon but not in a timespan that is relevant for humans.

                • Focusing on individual trees is the hard way to approach the problem. If you think about the ecosystem as a whole then it is pretty obvious that mature forests are carbon neutral. Sure there is new growth but that is offset by dead old growth decomposing. The biomass of the ecosystem remains about the same.

                  That is NOT true.

                  Process of decomposing is FAR FAR slower than the process of growing.
                  Walk through a forest sometimes. You'll find dead branches decades old. Meanwhile, a tree will regenerate such a branch within years.

                  Similarly, you'll find several layers of dead leaves one on top of the other on the ground - with new leaves on the trees. [shutterstock.com]
                  And that's WITH various forest critters munching on said leaves.

                  Meanwhile, them "individual trees" and their individual branches and root systems ADD UP rather quickly

                  • Process of decomposing is FAR FAR slower than the process of growing.
                    Actually, it is not.

                    And: it only affects the size of the depot of not yet decomposed old wood. You reach an equilibrium and from that point on it is carbon neutral, give or take 0.5%.

              • Branching and branch and tree girth.
                Obviously.
                And which trees do that? 100 year old trees that are full grown or 25 year old trees that still grow?

                Also, root system to support all that.
                Exactly. And which trees would do that .... ?

            • Re:Compensating (Score:4, Informative)

              by drinkypoo ( 153816 ) <martin.espinoza@gmail.com> on Tuesday May 08, 2018 @07:19AM (#56572730) Homepage Journal

              Sorry,

              No need to apologize, just provide a citation that supports your argument [time.com]. Otherwise, you really are sorry. A sad, sorry sack. Now look what you did, you baited me into proving that you know jack about shit, and jack just left town.

              • Sorry again,

                if you had a clue about physics you knew that your link is wrong.

                Only the CO2 that is converted into wood is "absorbed" by a tree. And that only works for trees that are still growing, not for trees that are outgrown.

                But perhaps you want to nitpick. Obviously a 1 year old tree does not grow as much as a 10 year old tree. Then again a 50 year old tree nearly grows not at all ...

                Pick your scenario.

                • Sorry again,

                  You never stopped.

                  if you had a clue about physics you knew that your link is wrong.

                  Kid, you have been completely and thoroughly schooled. If you still won't learn, you're incapable of being taught. One side, peck.

    • by jhol13 ( 1087781 )

      At least the ecosystem of a plant in the roof is a lot smaller than the ecosystem of a tree in forest.

  • by Anonymous Coward

    Dutch Elm Disease.

    • Dutch Elm Disease.

      Chestnut blight.
      Pine bark borers.
      Lady Eboshi.

      • Re: (Score:2, Funny)

        by Anonymous Coward
        Paul Bunyan.
      • by Ogive17 ( 691899 )
        Emerald Ash Borer has wiped out just about every Ash tree in the region... they get most treated ones as well. My town took the preemptive action to cut them down and replace them with other native species.
  • by sdinfoserv ( 1793266 ) on Monday May 07, 2018 @05:38PM (#56569954) Homepage
    On a positive note, that's an addition of 175,000 acres per year that are NOT susceptible to forest fires!
    • On a positive note, that's an addition of 175,000 acres per year that are NOT susceptible to forest fires!

      Not everybody lives in California...(ducking for cover...)

  • by 93 Escort Wagon ( 326346 ) on Monday May 07, 2018 @05:40PM (#56569962)

    What is the "just when they need it most" part? Is there a sudden, unforeseen shortage of firewood or lumber in the cities?

    I'm guessing the submitter must've been recently watching one of those movies where the hero's gun jams just as the bad guy comes around the corner with his own gun drawn.

    • by Anonymous Coward on Monday May 07, 2018 @05:51PM (#56570042)

      Google "urban heat islands." As summers get longer and hotter, the problem is exacerbated in cities due to low albedo surfaces, heat retention by high thermal mass cement and asphalt, and runoff of surface water that in other areas would be absorbed by the soil. As a result, cities end up being several degrees hotter than their surrounding regions. Vegetative cover helps to offset these effects.

  • by fluffernutter ( 1411889 ) on Monday May 07, 2018 @05:49PM (#56570024)
    This is one reason why I never left Canada. You have to move certain places to find it, but you can still find an affordable house on a well-treed lot, 20-30 minutes away from work here.
    • Yeah, but the work is building igloos.

    • Yeah, you would never find anything like that anywhere else in the planet. Only Canada.
    • by Strider- ( 39683 )

      You must be in a province other than British Columbia...

    • This is one reason why I never left Canada. You have to move certain places to find it, but you can still find an affordable house on a well-treed lot, 20-30 minutes away from work here.

      Got that in Michigan, not too far from one of the major cities. Of course now I'm putting 40 miles a day on my car, driving a route with no buses, compared to 20 miles a day when I was more in the city (driving a route that buses would have taken an hour and a half...). Win some, lose some...

  • As mentioned by others, trees can get sick and die. But, government agencies can (and usually do) over-react to finding any sign of disease or insect attack, and wipe out entire species from any area that MIGHT be affected. Find a particular beetle in a trap? All trees of that type within 500' are cut down within a week.

    One of the local colleges planted a lot of fast-growing trees around campus at the turn of the 21st century, as they expanded the "green spaces". Virtually all of those trees are gone now, r

  • Not a Choice (Score:5, Insightful)

    by Tablizer ( 95088 ) on Monday May 07, 2018 @06:18PM (#56570180) Journal

    Americans, already among the most urbanized people in the world, are increasingly choosing to live in cities. [Emphasis added]

    I don't believe it's a choice in the direct sense, but rather an economic reality. To be competitive globally and against automation requires high collaboration among experts and specialists. You mostly find this in populated areas.

    Farming automation has reduced the need for rural workers, and mining automation is also ramping up.

    If your job allows you to do remote work, then it more likely can be outsourced to Timbuktu for 1/3 your wages.

    • I moved to a big city because that's where the jobs are. Even in the moderately sized city I came from there wasn't shit for work. And the cost of living wasn't much lower either.
  • by ZorinLynx ( 31751 ) on Monday May 07, 2018 @06:22PM (#56570194) Homepage

    Here in Miami after Hurricane Irma I saw a LOT of trees being cut down that only had minor damage (maybe a branch or two down) from the hurricane. People would rather get rid of the whole tree rather than trim it back so it can recover after the storm.

    It was extremely depressing as my part of the city is already lacking in tree cover and this hacking and slashing just made it worse. So many people just don't care. One house in particular used to be almost completely shaded in the afternoons but is now in the sun the entire day. I bet their cooling bills will be far higher this summer!

    • exactly. Hopefully, if they are in the sun, they will add solar and use that to block the higher temps. It really makes a difference esp. for cooling.
    • Here in Miami after Hurricane Irma I saw a LOT of trees being cut down that only had minor damage (maybe a branch or two down) from the hurricane. People would rather get rid of the whole tree rather than trim it back so it can recover after the storm.

      Here in Lake County, California after our last massive round of fires, tree companies were literally stealing trees. They were coming around and cutting down trees on people's private property which were not damaged by the fire. They knew beyond any reasonable doubt that they were not supposed to take those trees, but they profit from taking them down both when paid by government and when they sell the resulting wood products.

    • I like trees. I want trees to shade my house.

      The roots of trees find your water pipes. The roots of trees insert themselves into those water pipes. A tree's gotta drink, right?

      Ultimately, I need to choose between trees or running water... or, I could spend thousands of dollars every few years repairing my water pipes.

      What do you think most people are going to choose? If your answer matches reality, then you are correct. If it does not, you either need to modify reality or deal directly with reality. Reality

  • Trees are bad for capitalism! Why have space- and resource-wasting nonsense like TREES when you could pave over that space and charge people to park their cars there? Or get rid of that completely useless public park and put up another high-rise office building, or better yet, luxury 'loft' spaces to lease out to rich people for HUGE profits?</sarcasm>

    ..yeah, sure. Just pave over the whole gods-be-damned country, especially with someone occupying the Whitehouse who wants to open up National Parks to
    • Actually, Tampa is a great example of just that attitude. They are now in SERIOUS water trouble and the temps have shot way up.
      • Actually, Tampa is a great example of just that attitude. They are now in SERIOUS water trouble and the temps have shot way up.

        The prime example in the USA has long been Los Angeles. They receive enough rainfall yearly to account for nearly 100% of their water needs, but nearly 100% of it runs off and goes straight into the ocean because they've paved nearly 100% of Los Angeles.

    • Yes! Nasty horrid treeses, They prevents us from getting the true greenses. Just to touches one burns us! Hsss! Hsss! - From "Are corporations really okay with this ring business?" by Sauron the overseer.

  • ... for drop bears.

  • But new developers bring in the cash.

    • Tax new construction that doesn't include greenery.

  • We used to plant loads of trees. And up in our mountains when we cut trees, we would plants new ones.
    Now, we have California size yards such that 1 and only 1 tree goes in.
    To top that off, here in the west, our forest have been devastated by pine beetle kill. That has done a real number on the pine, killing 1/2 of the trees. Thankfully, the spruce were hold up. Until now. Now, Spruce beetle is coming through with similar or same fungus that is killing them off.
    So, rather than harvest these trees AND r
    • Now, we have California size yards such that 1 and only 1 tree goes in.

      You know that California is one of the largest states, and still has tons of large parcels, right? I am just moving off of a 13-acre property in an ag zone.

  • We had a large maple in the front yard, but the roots were getting into the sewer line and we had to take it down. The other trees are still fine, but still it is a net loss.
  • by MoarSauce123 ( 3641185 ) on Tuesday May 08, 2018 @07:22AM (#56572736)
    From my experience the biggest threat to urban trees are utility companies. I understand that they want to protect their infrastructure, but they destroy the trees and call it "maintenance". Put all power and telco lines underground in conduits that cannot be damaged by tree roots. That will cost a fortune, but I bet the ROI is rather high. I can't imagine that it is less expensive to have crews and equipment on hand to constantly fix toppled poles and cut back trees.

    Another option is to go back to marking property lines with trees. I live in a neighborhood that was developed in the 1920s and on each corner of the properties is/was a tree. Not the most exact marker for property lines, but one that many appreciate. Trees keep water away from structures and give shade in the summer lowering AC cost. And they look nice.
  • Several years ago, I co-authored a book -- a photo history -- of the southern California community where I have lived for over 40 years. I reviewed old photographs of the area. I also recalled hiking over a hill into an adjacent empty valley that is now filled with houses.

    The interesting thing about all this is that what used to be open meadows with widely spaced trees is now so filled with trees that distant views are blocked. Almost every house has at least one large tree. Many houses have several. I

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