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Comment by snowwindwaves | Hacker News Reader

How much of your valuable land would you like to convert to forest? Unless we start paying people more to keep forests than they otherwise could in real estate, agriculture, etc it is a nice argument that trees can sequester carbon but unrealistic that it can happen on a scale large enough to move the needle.

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The thing I like about reforestation is that it's a positive, tangible, symbolic, easily understood concept that is likely relatively easy to get public support for. Conversely, carbon reduction campaigns feel more like being scolded. When I was young, the big environmental push was centered around saving the rainforest. I would like to see a return and expansion of this idea. It has many benefits beyond just global warming such as fighting desertification.

To be clear, I also support renewables and the other things listed by OP.

Sometimes I'm surprised how cheap land is. You can get an acre of grazing land for maybe 5 grand in the right area (if you buy in bulk), in a place conducive to rainfall and reforestation (Ireland).

I've looked at this and there are grants, but they're paltry (maybe a grand a year for 3 acres?) and you give up the right to do whatever you like with the land, like graze it.

I did some back-of-an-envelope calculations on converting beef grazing land (with its high methane emissions) to forest, specifically for Ireland

tl;dr - it's not cheap, but it's doable

A cow produces around 2.3 tonnes of CO2-equivalent emissions per year [1] You need 0.184 hectares of grazing land per cow [2] So each hectare of beef-grazing land emits around 12.5 tonnes of CO2-equivalent per year

Irish forests sequester on average 3.36 tonnes of CO2 per hectare per year [3] So converting beef-grazing land to forest offsets around 15.86 tonnes of CO2 per year per hectare. Cost of grazing land is around €25k/hectare [4]

Cost of planting a forest is around EUR3k per hectare [5]

So the cost of offsetting 1 tonne of carbon per year by converting beef-grazing land to forest is around €1750

Ireland's total emissions are around 61 million tonnes per year [6] So to offset it ALL would cost over a hundred billion euro, and a little more grazing land than actually exists in the country (and not all of that is beef anyway)

Or in other words, offsetting carbon by converting beef grazing land to forest would take around 1 billion euro per percent of our total current emissions. To put that in context - Irish govt spending is currently around EUR75 billion per year [7], and under the Paris Agreement we're committed to a 30% reduction of emissions by 2030 [8]

[1] https://timeforchange.org/are-cows-cause-of-global-warming-m... [2] https://www.teagasc.ie/animals/dairy/statistics-and-links/fr... [3] http://woodenergy.ie/media/coford/content/publications/proje... [4] https://www.agriland.ie/farming-news/2018-agricultural-land-... [5] https://www.teagasc.ie/crops/forestry/advice/establishment/r... [6] https://www.rte.ie/news/enviroment/2018/1205/1015300-greenho... [7] https://whereyourmoneygoes.gov.ie/en/2018/ [8] https://www.dccae.gov.ie/en-ie/climate-action/topics/eu-and-...

Thanks for that! Really appreciate it.

It explains why most of the forestry is on land not suited to a lot else.

Plus they just release it when they die.... that’s not a solution for petroleum and coal based carbon since it was environmentally sequestered before we dug it up.

Trees don't release CO2 when they die. They release CO2 when they rot. That might sound like an unimportant distinction, but for example buildings made of wood are a CO2 sink. The wood does not rot, and thus does not release the carbon bound in it. Basically burying trees (or generally biomass) in an oxygen-poor environment will sequester CO2.

Plus, if you do it in bulk, you are creating coal for future people, millions of years from now.

Don’t forget to throw in a few Dinos for the oil!

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