Is this really a shorter path than just planting more trees, which is both cheap and extremely low maintenance?
Burning fossil fuels can release an almost unbounded amount of carbon into the air.
So plant more trees? It's a continual process. It's not like you can plant a tree and say "Ok, I'm carbon neutral now!"
The current amount of carbon sequestered in all of the world's forests is ~600 giga-tonnes.
If we stopped all of our carbon emissions today, and tried to roll back to pre-industrial CO2 levels, we'd need to sequester ~270 giga-tonnes of carbon. Losing that much agricultural land is unrealistic - expensive as they are, it would be much less painful to switch our entire energy economy to renewables.
Re-forestation is part of the solution, but it's no panacea.
I hadn't meant to suggest it was. I'm merely saying that any approach to our carbon problem that doesn't include planting trees is inadequate.
Ahh, I misunderstood, my bad. I thought you were arguing that reforestation was not even worth the effort.
You don't need vast forests to capture carbon. You need one soon to be retired 30 year old panamax ship. A cargo hold full of ore (~50$/ton + 20$ powdering), and a on-board pump/aerator.
The burden of proof that "iron fertilization" (or any other geo-engineering technique) will even result in a net reduction in anthropogenic climate change — leaving entirely aside, you know, not actually being harmful — is on the people who want to do it. As much as CO₂, &c, is a problem that begs for something to be done, I don't think that's been adequately demonstrated yet.
ageofwant is satisfied that given the limited trials so far and the Russ George "experiment", which by all indications were wildly successful, large scale ocean seeding trials is called for.
Given the risks associated with doing nothing, and the relative low cost of a large trial, it would be silly, nay morally indefensible not to.
But the consequences of being wrong on some of the things being suggested to combat climate change could be tremendous, and in some cases even worse than the problem they're being used to solve.
I don't know where the balance that needs to be struck lies, but I'm pretty sure it's somewhere on the far side of:
"Welp, sounds good to me!" — some dude on the internets
Agriculture is a harder angle to attack; however, trees are excellent use of space: they store carbon for a period of time, they require low maintenance, they oxygenate the atmosphere, they can be planted cheaply and densely; harvesting them allows use of stored carbon (build with wood! Paper. Etc); they can be planted in areas that are typically not friendly to agriculture (eg mountains, places with extreme cold, etc). For the space we do have, there isn't much reason NOT to plant trees.
I would be interested in a comparison between different types of dense vegetation; eg trees vs grass vs moss vs algae, etc etc.
The obvious solution being to increase carbon/biomass per hectare in our urban and agricultural land.
>Losing that much agricultural land is unrealistic
Losing it, yes. But replacing it with agroforestry and soil building no-tillage agriculture would increase the food supply (mainly since bare dirt monoculture fields are so abysmal at utilizing sunlight compared to healthy engineered ecosystems). Similar story with replacing corn-fed CAFOs and compacted ranch land with sylvopasture and MIRG (managed intensive rotational grazing).
If it sounds unrealistic to replace our whole food system with something else, remember that there is no alternative. The modern industrial food system isn't a viable replacement for itself. That's all the word "unsustainable" means: it's not an ethical judgement, but a logistic certainty.
Dense planting means the canopy can prevent rain getting to the ground and the trees take a lot of the water that does get to the ground which means aquifers are not replenished.
The dry ground and dry trees pose an increased fire risk. Burning the tree releases any captured carbon, and a bunch of smoke.
New forests crowd out and change existing eco systems, meaning many animals are lost to the area.
Trees shade soil reducing evaporation levels. Trees also significantly reduce surface winds further reducing evaporation. Yes trees do potentially use more water which is exactly what you want, what is the purpose of full aquifers flowing into the sea ?
In Australia removal of trees has lead to increased salinity levels affecting 2 Million hectares (In WA alone) of arable land degrading vast swathes of it rendering it unusable for both modern agriculture and pre-agricultural "natural" use. This is precisely because the trees kept the high-salinity water table below surface root levels.
I'd be happy with merely replacing some of the forests that we cut down in the first place.
You know, if we're going to make arguments premised on human activity altering extant ecosystems, and all...
[0] https://en.wikipedia.org/wiki/Deforestation_during_the_Roman... [1] https://en.wikipedia.org/wiki/Geography_of_Iceland
7 billion people. Wood is not 100% carbon and a wood house is ~30 tons of wood. But, there is not a house per person and people don't build new houses every few years.
Biochar can be continuously applied on fields to improve degraded soils, and its production from woody biomass is energy positive and inexpensive.
I say this because the volumes of CO2 capture necessary for the two degree scenario (that we all just committed to in Paris) are so beyond the scale of almost anything we manufacture that it's not even funny.
We're talking thousands of Hoover dams full of liquid CO2 that has to be captured, transported and stored every year.
It's just that doing something impossible is tricky.
Time-to-rot varies, from 50-100 years for a spruce, 200-300 for a pine.
I've witnessed downed redwoods myself, over the course of four, nearly five decades, which have failed to decompose even in highly damp conditions.
Bogs and swamps are also underappreciated CO₂ sinks.