that's only 160 trees per person...

To put the number in perspective, that's a 40% increase in the estimated number of trees worldwide. That's a positively enormous increase, and would--by necessity--in large part be planted on and around existing agricultural land. That comes with a host of significant opportunity costs; just to start, population increases are projected to require a ~70% increase in food production from 2005 to 2050[0]. While there's a great deal of progress being made in improved agricultural efficiency and food waste reduction that will help lessen the environmental impacts of that increase, land for food production is still likely to directly compete with biomass plantations for carbon removal.

There are also recent studies that highlight some of the potential environmental impacts of large-scale terrestrial carbon removal as a primary mechanism for reversing the effects of climate change. Optimizing for sequestration means converting the most productive agricultural land or using even more natural land, devastating either food production or natural ecosystems,[1] in addition to drawing heavily on water resources and fertilizers on a massive scale, risking other planetary boundaries.[2] The more realistic scenarios risk both, albeit to less catastrophic degrees, but do so by decreasing potential sequestration and limiting its effects on global temperatures. Put a bit glibly, it's jumping out of the frying pan into the fire.

That's not to say that it isn't part of the solution. It is, as the first paper explicitly states in its conclusion, and "can significantly contribute as a “supporting actor” of the mitigation protagonist, if it gets started and deployed immediately." But it won't be a primary mechanism, nor will it reach anywhere near 1.2 trillion trees. Even the more limited "pertinent options available now, which include reforestation of degraded land and the protection of degraded forests to allow them to recover naturally and increase their carbon storage" need to be priorities.

Other geoengineering proposals, such as possible solar radiation management techniques, might extend the period during which we can use tCDR and other carbon removal mechanisms to mitigate past emissions beyond just slowing the rate of temperature increase. But without drastic emissions reductions in the immediate future, all of those possible options become more difficult, with even more deleterious consequences. Not to mention more expensive.

In other words, there's no easy or even optimal answer. Assuming, of course, that 1.2 trillion trees can be considered "easy."

0. http://www.fao.org/fileadmin/templates/wsfs/docs/Issues_pape...

1. https://pdfs.semanticscholar.org/a712/e761c2360f927cbff0ee54...

2. https://www.nature.com/articles/s41558-017-0064-y

At one tree per second It would take 38000 years to plant 1.2 trillion trees. This proposition is beyond our currently available resources.

Everybody just keep doing what you’re doing, because problems could be solved, hypothetically.

Even though planting trees seems like an overall good idea (and I certainly believe so), I recall a recent article where scientists debated whether planting trees will have any impact.

From https://www.nature.com/articles/d41586-019-00122-z

> Several analyses in the past few years suggest that these warming effects from forests could partially or fully offset their cooling ability.

What's consoling is that at least planting trees is unlikely to harm (although rapid tree plantation will certainly send ripples in the complex, inter-connected ecological chains).

Not cutting down rainforest, and encouraging their expansion again, seems a far better plan somehow.

The satellite images of continuing, and still accelerating, forestry loss were the most striking part of Attenborough's Climate Change prog for me.

I think we need a system, where the rest of the world will pay countries like Brazil or Indonesia to keep their current rainforests.

Currently, we are paying them to cut down rainforests and plant oil palms, so that we can buy cheap oil from them.

An easy way to contribute to tree planting is ecosia.org (more info at info.ecosia.org). We've already planted more than 55 million trees and won't be stopping there.

Noob question here: what is stopping nature doing this, seeds and all that?

I made some rough calculations yesterday and user strainer corrected me: https://news.ycombinator.com/item?id=19701879 It would seem that even with his corrections and this article's data capturing carbon isn't feasible. 1.2T trees increases earth's forestation by 40% but only nets us 10 years of emissions. It seems very inefficient in relation to trying to reduce emissions.

People wonder if we have the space to plant these.

How about creating giant floating tracts of mangrove trees. They’re naturally able to live in saltwater.

Maybe make the islands out of waste plastic.

Yes! And you can do so at the tune of $0.10 a tree. To offset your CO2 emissions, you need to spend $15/person/year (if you're an American resident). I wrote a blog post about it here: https://automicrofarm.com/blog/2019/03/solving-climate-chang...

I hope this is the American version of a trillion and not the British.. googles how many billions are in a trillion and got back

“In the American system one billion is 1,000,000,000 and a trillion is 1,000,000,000,000 so one trillion is one thousand times one billion. In the British system one billion is 1,000,000,000,000 and one trillion is 1,000,000,000,000,000,000 so one trillion is one million times one billion.”

So, to plant this many trees, you need Gene modification. The tree sapplings have to be toxic to sheep, heat & dry resistant, and they need to be non harvest able. You need to engieer a plant that is economically uninteresting for humans. Then distribute it via drones to the post human desolation.

  Australia has announced a plan to plant a billion more by 2050 as part of its effort to meet the country’s Paris Agreement climate targets.

Laudable, but a tiny fraction of the 1.2 trillion mentioned as offsetting a decade of co2, and over a period of 3 decades.

CNN coverage: https://www.cnn.com/2019/04/17/world/trillion-trees-climate-...

You don't cure cancer taking painkillers. You should both go after the symptoms (if they are bad enough at least, that they are now) and the root cause, because if you don't solve the real disease the symptom mitigations will be shortlived, as the patient.

For reference, there’s about 500 trillion square meters of land area on the planet; so even if trees are crowded together one per square meter, this is talking about a 500th of that.

But perhaps we can find a way to make the Sahara into a forest? That’s about what it would take.

This is a greet solution to a problem only half the population believes exists.

I wish the government gives money or tax credit to home owners for planting trees, like X amount for first year and a little bit more every year for the next 5 years, instead of the punitive approach some cities taking now.

This is one global-scale geoengineering project I can rally get behind. It has the smallest chance of catastrophic second-order effects of any of the several methods I've heard of.

I wonder how increasing the forestation of the planet by 40% would affect the planet's average albedo, and by extension the solar thermal energy retention.

We need to stop buying stuff we don't need, chucking food we didn't eat, and eating beef like there's no tomorrow.

If only every person in the world could plant roughly 150 trees...

I mean, this is a great conclusion, but what are we supposed to do with it?

Its hard for me to plant a tree, but I could expand my garden or add a bush. How many gardens are needed to equal a tree?

Any donation organisation which convert donated money into trees and keep them alive or other co2 activities?

Size aside, we need to plant some 15 Billion trees a year just to break-even on trees.

If there’s land for them to be planted let’s do it!

I likely would, with caveats.

There could be an even cheaper scheme for climate change mitigation that we haven't thought of (like stimulating plankton growth with iron, for instance).

And it's actually possible that the total cost of allowing climate change to progress unmitigated may actually be cheaper than 50 cents per ton of CO2; creating more fertilizer for farmland and building seawalls may become cheaper 100 years from now than the future growth-adjusted value of the proposed carbon-based tax credits.

Unfortunately it relies on volunteer villagers with unused land so there's a limit to how much capital could be deployed that way.

Find a group that makes this happen in local parks and forests. Help them.

Livestock eat to extract nutrients. Their waste is not more nutrient rich than the stuff they eat. That would be impossible.

Another way to know your number is wrong is to consider the fact that the US emits ~5.5 gigatons of CO2 per year. If it cost only $1 a ton to sequester that then the total cost would only be only 5.5 billion dollars a year.

That's....not very much at all. Global warming wouldn't be a problem if Jeff Bezos could fix it by himself.

I think it predated that in that it occured with even slow "colonization" (regardless of it being occupied or not) but that is a good point. Expectations shape it first.

In Florida they are also very risky because they tend to destroy homes when they topple during a hurricane.

While I agree with the sentiment of the GP, the reality is starkly different.

Most people I know go to great lengths to remove trees near their house. Some insurance companies lower premiums for it.

For any elevated property it adds a huge amount of value to kill a nice old established tree in the way of views.

The enormous snapping turtle that visits has chosen not to eat my children, I like that.

Ah, so we've been trying to do good all this time with industrialisation!

In addition, while planting a tree costs only a few dollars, cutting down a 100 ft high tree in an urban space can easily set you back thousands of dollars.

I've had several trees fall this year, on or around my house. Wet year, and windy too. If they're near your house, you need to invest in making sure they're healthy trees! I'm thinking of planting new trees further back from the house, near the creek.

Why do you have a flat roof on a house that's surrounded by trees?

Biochar can be produced (and is) by burning off the hydrogen. This is done by restricting oxygen availability, which the hydrogen preferentially bonds with. When the hydrogen is used up, you are left with charcoal, which powdered and mixed into the soil improves it wonderfully.

Look up "terra nigra", invented in the Amazon basin.

Maybe put up solar in places there already isn't forest.

One analysis I read some time back claimed that Trees are net positive when they are closer to equator, IIRC 30deg each way. fortunately for this topic, the areas close to equator are also significantly poorer countries thereby maximizing the roi of a fixed dollar expense.

Overall I believe that if a functioning carbon credit marketplace is established we can fund the whole green movement with a fraction of world GDP and might even end up creating a whole bunch of jobs doing it.

There are essentially none where I live in SoCal (which actually bothers me a lot, because of how short-sighted it is but also because I grew up in the midwest and I genuinely miss having trees around). Most of the newer developments that I see and giant sections of LA and Orange county where I spend some time are little more than a sea of asphalt. There are trees in parks, of course, but they're more like decorations than something that serves a function.

The fact that you presume people outside the US know what and where "Michigan" is makes me think you don't know much about other countries at all.

UK for me, never heard the term.

I once worked for a short spell in a tree-planting squad in the highlands of Scotland. The seasoned planters were olympically fit and each planted around 100 saplings an hour across rough mountainside.

Couldn't say.

Whatever you do, if the target is reducing CO2 emission, you'll have to account for the CO2 investment. All I am saying is it may be more cost-effective to leave the desert alone and put our Trillion trees where conditions are already great for large trees (Alaska, NZ), instead of pipe-dreaming about Roman aqueducts delivering water to a green Sahara or Gobi.

It gets malicious real quick when they invoke the power of the HOA to force you to tame the wilderness in your back yard. :(

I’d love to see better off-the-shelf solar purgolas, gazebos and other shade generating buildings like that (partial shade greenhouses, maybe?).

The backside of solar panels are actually quite pretty, and provide shade + partial rain barriers.

This would open up more avenues to passive cooling and also reduce the lock-step replacement of the house’s roof with solar panel installation .

It’s cheap to plant baby trees, and baby trees are the ones that are about to go through their main carbon absorption cycle anyways.

It is not difficult but doing it without the right machinery requires back-breaking labor. It looks like this: https://www.youtube.com/watch?v=uUzeruQT8xE I did it one full weekend and I was totally exhausted. Of course, there exists machines to do that, but then you can't have every person in the world chipping in.

But planting is just the first step. If you own a growing forest it needs to be culled periodically, meaning that you cut down the worst performing 10-20% of all trees.

With everybody trying to burn it, or steal it, or pour concrete over it, can be very hard.

Is an 80 years' work in any case.

Making your transmission line a lot longer doesn't scale your losses by that much surprisingly. The main transmission losses are at the conversion points and in the utility voltage cabling at the end, having long distance interconnects really only loses a percent or two over having short ones.

Right, but if the point of planting the trees is carbon amelioration, than carbon neutral would somewhat defeat the point.

I've seen this argument before, and I think the real place it falls down is that there just isn't that much space. For mature growth forest, you have something like 40-ish big hardwood trees per acre [1]. Those are, to my understanding, the only ones that are really relevant because they make up most of the biomass. Other types of trees are just a rounding error. `1.2e12 / 40 acres -> square miles` (frink) is 4.7e7 square miles. That is more than the whole land area of Earth [2]. There is certainly not enough land that would support mature forests available to plant so many trees, unless I have made a serious calculation error.

[1]: http://www.sbcounty.gov/calmast/sbc/html/healthy_forest.asp

[2]: https://hypertextbook.com/facts/2001/DanielChen.shtml

And burning trees is better than letting them rot, which releases methane.

Which Carbon though. Trading CO2 for CH4, for example, would not serve us well.

I dislike the US prison system but perhaps we could use prisoners to do it. They could plant hundreds If not thousands within a sentence and one day return to visit the forest they planted.

Planting is something we know really well how to automate, though. Planting is the most tractable problem in this (hypothetical) solution.

Also, more rain means more clouds, and this is something the current climate models can't really model accurately, believe it or not. There's not even "consensus" on whether clouds are beneficial or detrimental.

If each person on the planet would plant 150 trees this year, we would be finished.

Well, we have better means for automation now. But I'm just fascinated how quickly that solution pops up in such discussions as soon as it's convenient.

I don't think planting trees is the biggest issue. Access to water is. More practical solution would be to fill some desert with sea water and grow plankton, kelp etc.

That’s the price of the seeds though. The cost of finding the land, digging holes, planting seeds and watering them to sustainable growth would be much higher.

Honestly if HN knows any charities focused on tree planting, let me know. Happy to donate 1k-ish if it puts 10k trees to our family’s name.

Is that just for the seedlings and not the actual labor of planting them?

I've seen quotes for parts of developing countries where planting trees would cost $100 USD per thousands trees.

See FAQ point #11: https://trees.org/faqs/

> 40 dollars to plant a thousand trees

Presumably these would be some of the cheapest trees to plant. When that space is used up but the first few billion trees, where will the next billion go? How much will that cost?

trees are only a co2 buffer, they don't make it dissappear. and trees require water, and the burn up (which puts the c02 back also)

If you don't see labour camps as a form of modern slavery, then I'm genuinely asking you to provide the definition you've learned back at school.

The best way for sequestering wood is turning it into biochar. You even get some energy out of it.

Why not do something more useful and sequester the trees in buildings? Timber-framed houses for everyone!

Or use the wood in construction.

Except for those two huge externalities that are never priced in and always overlooked by people who say nuclear is 'clean': the waste that will remain toxic for a very long time, and the risk of accidents (slim, but the consequences are really, really, really bad).

I’m pro nuclear power, but I also understand that politically and economically it’s a non starter. At this point in time it’s either solar (or wind) or natural gas. I’ll take the known local maximum over a global maximum that’s not feasible.

Does this figure factor in the $100 billion cost of the Fukushima disaster?

Saw some urban foxes in Montreal - a tourist left a backpack with his dinner (rotisserie chicken) on the ground while the group went to take photos, upon their return they discovered that the foxes were already splitting the “catch”.

California has some raccoons and coyotes. Haven’t seen foxes in cities, but we do have them in the countryside.

There are some suburban ones but they tend to be pretty skittish - you generally see them through windows or cameras. I had one funny experience where they apparently moved stealthily enough that the motion activation mode on a security camera had them appear to teleport - it showed up for a few frames, appeared elsewhere in frame and then disappeared.

Really it is tameness that does it as they don't scatter before we even see them. The woods being quiet is because we scare the hell out of nearly everything, constantly walking on two legs like a bear ready to fight. Leave cameras behind and it gets noiser and more active.

I routinely come across coyotes in my neighborhood. Just this past week, I was out walking my dogs at 11AM and had one emerge from the bushes in the middle of a residential neighborhood. It was being harassed by a Blue Jay. It came within about 5 meters of my dogs and I, while we stood off the to the side to let it get past us and head towards the dry creek bed that they use to navigate the area. They're in our neighborhood for the rabbits.

I'm on the edge of the urban and rural suburban world so most wildlife is still a bit more wary, but yeah the urban foxes a few miles from me are far far less shy.

We have coyotes in many suburban areas.

I live in Minneapolis Minnesota. We have raccoons, opossums, squirrels, rabbits. That's all I have seen for small ground critters that aren't living in parks.

Not so much, I think. In the upper Midwest, it’s mostly squirrels and rabbits.

I can tell you how I reason to it.

According to many sources, but I will cite this one[1] a single tree converts about 50 lbs of CO2 in a year. There are three trees on my property, a city tree (planted by the city) and two Birch trees planed by the original developer. All are deciduous so lose leaves in the winter but we'll give them full credit anyway, so call it 150 lbs of CO2 a year.

My rooftop solar system nominally puts out 5.2 kW of power under full sunlight, although efficiencies cut that down to around 4.8 kW net into the grid. I have over 10 years of data from the system, drilled down though it averages out to about 4.5 "solar hours" per day with an average daily output of about 22 kWH per day or about 8 MWH per year.

The US Energy Information Association (EIA) tracks a number of statistics, but the one that is most relevant is the number of metric tons of CO2 per MWH per state. You can see California's number in this report : https://www.eia.gov/electricity/state/california/ is 474 lbs per MWH.

Using that number, my rooftop solar system "saves" (which is to say doesn't generate) about 3,792 lbs of CO2 a year. Which, is way more than the 150 lbs a year the trees are taking out of the air. This is why the 1.2T trees, or 160 per person, is such a large number. A family of four would need to plan 640 trees on their lot, which would remove 32,000 lbs of CO2, which is a lot. To match my solar panels I would need to plant an additional 76 trees.

What you can take away from that is that solar panels in places where you can't put trees are a solid alternative. And planting trees rather than letting unused land sit idle as a field of grass is also a good plan. As a home owner, solar, even in places where it won't generate all your energy needs, will help cut CO2 emissions.

[1] https://projects.ncsu.edu/project/treesofstrength/treefact.h...

That’s pretty trivial to prove. Grid tied systems sell excess electricity back at bulk rates, at least in some states, which means that the solar panels are producing more electricity than the home needs for cooling. Thus such a house is actually spending negative carbon on cooling, since they’re providing green energy for their neighbors.

A shade tree can reduce your need for electricity, but it can’t turn you into a net producer.

It can be shown both bottom-up and top-down, but I prefer the bottom-up: Photosynthesis is usually an order of magnitude more efficient than photovoltaics: https://en.wikipedia.org/wiki/Photosynthetic_efficiency

...an individual leaf might be peak out at 3% efficient, but it is operating just a portion of the year (maybe about a third to a half at full performance) and also much light gets reflected, absorbed by branches, or misses the leaves entirely.

Additionally, photovoltaics peak at 40% efficiency but get about 15-20% efficiency typically and can function the entire year (unless fully covered by snow). And they're displacing electricity produced primarily from fossil fuels which are burned at 30-40% efficiency.

Now from a top-down perspective: forests (in this case calculated by replacing cropland with forests) are estimated to sequester about 2 to 10 tons of CO2 per acre per year. https://fas.org/sgp/crs/misc/R40562.pdf

In principle, an acre of about 40% solar photovoltaic system with a 25% capacity factor could produce about 3.5GWh per year. But typically, about exactly one tenth that is done in practice: 0.35GWh/year/acre.

Since you'd be displacing electricity from the US grid, which is currently about 420 grams of CO2 per kWh (based on my calculations of the most recent eia.gov figures, but you can find similar figures by Googling), that's equivalent to 147 metric tons of CO2 per acre per year for typical photovoltaics (and over 1000 metric tons per acre per year in the idealized case).

This person's calculations reach similar conclusions: https://www.solarpowerrocks.com/environment/installing-solar...

So absolutely, it's better to use solar panels than trees, at least until the grid is fully or nearly-fully saturated by solar.

...BUT once we fully clean the grid, trees have some advantages: 1) they efficiently suck CO2 out of the air and store it, not just produce the energy. That means you can actually draw-down CO2, producing negative emissions. 2) They're scalable. A tree is like a solar farm, CO2 direct air absorption system, and a chemical factory but can be planted as just a seed. It may not be "efficient", but being self-replicating and scalable is pretty powerful.

I suspect this is because you generate power all year round, while a shade tree doesn’t help heat your house in winter..

Hyde Park

But the comment said we could get energy out. Wouldn't we burn it to get energy?

Search past HN posts or look it up on Wikipedia, it's been discussed many times.

Even if it's true, it's like using "there are more deaths by vending machine per year by shark" to justify everyone swimming with sharks. Not saying that nuclear is inherently unsafe, but if 100% of our power came from nuclear, then so would 100% of the deaths per MWh.

Don't quote me on this but from memory a tree is able to sequester a lot more in the first couple of years than as a fully grown tree. Intuitively that makes sense.

Yea, so to sequester the carbon either build something out of it or dump it into the ocean. Maybe build a boat?

That's just comparing them with coal to sound great. The three major nuclear accidents do not represent the worst which nuclear plants are capable of. For example we have yet to see what can happen if a nuclear plant is sabotaged - that's not FUD its a real vulnerably of the technology and is a reason why they incur constant exceptional security as well as safety costs. They consume alot of water resource as well, for cooling.

Thankfully its an academic debate now anyway, because solar and wind prices are already much cheaper with no end to their continued improvement in sight.

We can and should, but there's more impact to be had from ceasing to dig up the buried carbon and burning it. That's the equivalent of not punching holes in the hull, whereas planting trees is like bailing out the boat -- you'd rather it just didn't leak!

There were personal heroics but the Soviet response was a catastrophe, it was Sweden that sounded the alarm and the Soviets allowed a May Day parade of children to march through the cloud in Kiev...

"For 36 hours after the explosion, people were given no reliable information about it and left virtually on their own. They never received instructions on how to protect themselves and their children. Radiation levels that according to Soviet laws were supposed to trigger an automatic public warning about the dangers of radiation exposure had already been recorded in the early hours of April 26—but were ignored by one official after another. Finally, people were asked to gather their belongings and wait on the street..." https://www.history.com/news/chernobyl-disaster-coverup

https://www.nationalreview.com/corner/remembering-soviet-res...

> One effort that stands out as "preventing something much worse" is that there was a risk of a potentially larger secondary explosion from steam buildup.

A larger conventional explosion would have been linearly worse, not worse rising to a separate category of problem.

> Also, you can absolutely get a nuclear explosion from a reactor, there is some suggestion that Chernobyl might have been a small one in fact (paper)

This is not what I'm referring to. It's one thing to have a "nuclear explosion" in the sense that the reaction generates enough heat to cause the rapid expansion of gasses which is technically an "explosion".

What I'm referring to is the sort of exponential chain reaction that happens in a nuclear weapon, resulting in something on that scale. You have to design for that on purpose to get it. The density and geometry has to be exactly right.

> you can absolutely get a nuclear explosion from a reactor, there is some suggestion that Chernobyl might have been a small one in fact (paper)

An explosion that's too weak to even blow apart its own assembly doesn't count.

> No offense but if you can't see how Chernobyl or Fukushima could have turned out worse, or that unexpected accidents in other locations could happen and could be worse, you don't understand nuclear power.

I can't help but notice the lack of specific examples or explanations of any kind.

> Water resource is consumed, sure it rains again - often far away and into the sea. Fresh water resources are scarce and under pressure in many places, ancient aquifers are drying out, particularly in the US.

Ancient aquifers are drying out as a result of unsustainable resource management and climate change. Nuclear power helps with both of these, the first by providing power for desalination and the second by reducing carbon emissions. The amount of water it evaporates for cooling by comparison is a drop in the bucket. Also, the cooling can be done with seawater to begin with.

> Water resource is consumed, sure it rains again...

And sometimes ocean water is rained back on land. Hurray, water cycle!

Actually - most desalination is done by reverse osmosis - which is much more efficient than evaporation.