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I've read answers that outline how if we afforested large (continental-scale) masses of land, it would do little in the way of tackling climate change. While it would sequester $\small\mathsf{CO_2}$ for about a century after it was planted (while growing) before reaching equilibrium, the planting of large quantities of trees would also sufficiently decrease the albedo of the land in which it was planted, that it would hold in a lot more heat than the land it replaced (likely desert or otherwise barren land). This means that, all things considered, it would make a negligible, if not negative impact, in tackling global warming.

If this is the case, why do we associate "planting trees" as a good thing, on the scale of individuals planting individual trees? Is it because generally, these trees improve ecosystem vitality/diversity, or for some similar reason unrelated to climate?

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  • $\begingroup$ [citation needed] re the albedo claim. $\endgroup$ – Semidiurnal Simon Oct 15 '19 at 18:53
  • $\begingroup$ People planted trees long before climate change was even an idea, tree planting festival started in the 1600's also consider arbor day. $\endgroup$ – John Oct 20 '19 at 0:49
  • $\begingroup$ It may not do much for climate change but it does help preserve wild spaces and the biodiversity that depends on them. $\endgroup$ – John Jan 14 '20 at 6:25
  • $\begingroup$ @John But what if a Australia like situation creeps in ? Then trees just add to carbon sequestration in the atmosphere ? $\endgroup$ – gansub Jan 14 '20 at 7:14
  • $\begingroup$ @gansub you are going to have to be more specific, Australia has many "situations" $\endgroup$ – John Jan 14 '20 at 14:58
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Planting trees has a short term benefit in carbon sequestration but will not offset the carbon from fossil fuel burning. However, in some places trees provide a benefit of increasing soil carbon which can have a longer lasting effect. Thus, one benefit is to increase the time needed to implement replacements to fossil fuels. Trees can increase cooling through greater evapotranspiration than grassland, in some climate zones. That, however, may have an impact on water resources. Wood and paper products that are not recycled remove carbon from the natural system, although the effect is small.

Burning wood instead of fossil fuels has a positive impact on the carbon budget where the carbon is recycled back into tree plantations.

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  • $\begingroup$ trees that throw deep roots will more likely retain moisture better than trees with shallow roots. So at least trees can also prevent water from escaping into the atmosphere as water vapor another green house gas. Yes ? $\endgroup$ – gansub Jan 14 '20 at 7:28
  • $\begingroup$ No. Trees pump water into the atmosphere. In general (not always the case), evapotranspiration from forests is greater than from other vegetation. $\endgroup$ – haresfur Jan 16 '20 at 4:50
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Because the first few decades are crucial, so we are pragmatically buying time until we manage the transition from fossil fuels to clean energy sources.

I heard a podcast announcing Ted's initiative called Countdown, where they presented planting a trillion trees as a solution. A company Flash Forest is being founded on Kickstarter to the amount of 100k to plant a billion trees with drones.

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Timber, shade, nuts, fruits, animal habitat, flowers, landscaping, erosion control, poles for electric power distribution, syrup, spices,coffee, and other things unrelated to global warming.

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  • $\begingroup$ Of the many reasons I have planted over a thousand trees, not one was planted to collect carbon. $\endgroup$ – blacksmith37 Oct 15 '19 at 18:45
  • $\begingroup$ Decades of consistent science based expert advice should not be dismissed as hysteria. $\endgroup$ – Ken Fabian Oct 29 '19 at 11:01
  • $\begingroup$ But none of the "scientists" have ever done a basic calculation to determine the degree of correlation, if any, between the two independent variables of global temperature and atmospheric CO2 ; That is normally the first step in actual science. Correlation is a mathematical factor that varies from 0 to 1. $\endgroup$ – blacksmith37 Oct 30 '19 at 0:12
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    $\begingroup$ I notice the objectionable bit has been edited out. Rightly. The US National Academy of Sciences - as just one example - is satisfied the link between climate change and CO2 from emissions is real. "Scientists have known for some time, from multiple lines of evidence, that humans are changing Earth’s climate, primarily through greenhouse gas emissions." I trust the experts they draw on to know what is valid science and what is not. $\endgroup$ – Ken Fabian Oct 31 '19 at 4:32
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Take a look to the Carbon Cycle.

In the atmosphere there is around 700 Gt of carbon, most of it CO2. The living biomass (plants + animals) keep 600 Gt and the dead biomass is 1000 Gt.

So biomass it is very effective in order to fix CO2 as it is fixing in 2 ways: photosynthesis (absorbing CO2 and emitting O2) and, when biomass dies, then it is fixed on the ground.

When you deforest, you are removing the biomass that takes some direct CO2 and you are exposing or removing the carbon fix on the ground.

Really, they are not the main actors on the picture: Oceans (38,400 Gt, lithosphere carbonates 60,000,000 Gt, lithosphere kerogen 15,000,000 Gt) but their cycles takes 100 years on the fastest one and hundreds of million years on the slower. But the fastest one is the biomass, and the most effective one is the tree. (Check Kiri tree)

Take a look

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Planting trees is a good thing provided it is done properly. In Britain we have some valuable habitats such as heathland, peatbog, and wetland where planting trees would do ecological damage. If for example you managed to put a small stand of trees in an area of wetland, that would encourage hawks and corvids to take up residence to the disadvantage of wetland wildlife, and it's the same with heathland and peatbog. I doubt if it is possible to plant enough trees to make a major impact on the CO2 problem, but they will make some difference if only a small one, and in the right place can be a wildlife asset as well.

It would be impossible to grow trees in most true deserts, but in the Namib and Atacama there are places where sea mists roll in from the sea and condense on any object which protrudes from the sand. Maybe it's possible there. The most promising place for tree planting is in restoring the S.American rainforest, where there could be a huge environmental benefit. It could be financed with foreign aid money which wold go direct to impoverished rural communities, thus killing several birds with one stone.

There is a scheme underway in Britain to encourage the spread of sea grass meadows, which are important to the marine environment and apparently are more efficient at sequestering carbon than most things you can grow on land. Again the contribution will be small, but better than nothing. Sea grass is a true grass, but somehow manages to grow completely submerged in shallow salt water. Few people are aware of its existence. Restoring mangroves, which are basically small trees able to grow in tropical estuarine waters, is another area of environmental improvement which would also assist in the battle against CO2.

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    $\begingroup$ doesn't answer the question. $\endgroup$ – gansub Sep 15 '19 at 7:38
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    $\begingroup$ People plant them for the reasons I state in my answer. As I give users credit for a modicum of intelligence, I didn't think further explanation would be necessary. $\endgroup$ – Michael Walsby Sep 15 '19 at 7:48
  • $\begingroup$ Something like this is required - earthscience.stackexchange.com/questions/2639/… $\endgroup$ – gansub Sep 15 '19 at 12:27
  • $\begingroup$ Nowhere in the answer did you actually say why planting trees is a good thing. Instead you answered how to grow trees improperly, a location where growing trees might be helpful ("huge environmental benefit" yet not explaining why), and then a random tangent about another plant. As I give answerers credit for a modicum of intelligence, I'm assuming you misread the question. $\endgroup$ – personjerry Sep 18 '19 at 20:06
  • $\begingroup$ Tree planting also helps reduce flooding theecologist.org/2019/mar/14/planting-trees-tackle-flooding $\endgroup$ – MiguelH Oct 15 '19 at 9:36

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