I was wondering, which vegettion acts as a larger carbon sink-grassland ot woodland? It would seem (to me) that a grassland would absorb more carbon-more leaf area per square mile. But trees produce wood (a concentrated carbon sink)-so which is preferable? Would it be a majot tragedy if grasslnds replaced the Amazon jungle?
There are two questions here: one concerns the rate of carbon conversion and the other the “carbon-sink” effect.
Essentially any area of stable vegetation is carbon-neutral: the amount of growth each year is matched by the amount that decays. So while certain types of vegetation may convert more carbon per unit time, the net long-term effect is the same.
The efficiency of vegetation as a carbon sink can be decided by looking at the total mass of vegetation per unit area. By that measure, trees are typically far more effective than grass.
What’s carbob? Is it related to Carob?
There are many problems, but a significant one with any monoculture, planing all of the same thing, is the sudden loss to disease. There’s also the issue of a runaway forest or grassland fire, suddenly returning your “banked” CO2 back.
Think of vegetation as a carbon bank:
the bigger the vegetation - the more carbon it has stored, &
the faster the vegetation grows, the more carbon/year it can store.
Grassland might grow fast, but unless you have some way of removing the clippings every year and putting them in a giant air-sealed vault (or some sort of subduction zone), they aren’t going to store much total carbon. Once the grassland has generally reached it’s maximum historical height, it’s saturated -it does you no good after that. Contrast that with a forest, which can keep growing and banking carbon for a hundred years, and if it’s turned into furniture, the carbon can be stored for much longer than that.
Here’s a link to an EPA table showing carbon sequestration rates. Note that “Afforestation” has a sequestration rate of 0.6-2.6 metric tons of carbon per acre per year.
This (afforestation) is the rate for changing from croplands/pasture to a managed forest.
That question is currently the focus of a lot of research. IIRC, there really isn’t a single consistent answer. Young forests that are still growing in height and density are definitely major carbon sinks. Same thing goes for a grassland, but that’s obviously a much shorter process. In most cases mature environments are carbon-neutral. Some are carbon sinks still, as they continue to deposit organic matter into the soil, faster than it can be decomposed. Again, IIRC, there are some mature grasslands that behave like this. Some very old forests will be carbon sources, as big ancient trees start falling and decomposing faster than they can be replaced.
ETA: One thing to consider with grasslands is that they can continue to deposit material deep into the soil, through comparatively large root systems. Most of the stored carbon in a grassland is underground.
I asked Bob, and he told me he’d seen more wrecked cars pushed into the ditch in forested areas than in “grasslnds”. He was unable to comment on how “majot” this tragedy might be.
I apologize if I didn’t answer the question as asked. I went with my interpretation of an either-“ot” situation.
What we’d want is to tree Sahara.
There’s one complication that applies to global warming but not so much to carbon dioxide specifically. In parts of the world where there’s snow cover for a good part of the year, trees can have a net warming effect: http://www.sciam.com/article.cfm?id=tropical-forests-cool-earth
The loss of the Amazon Rain forest is a very different catastrophe than just the stored carbon. I think about two summers ago, parts Brazil suffered serious problems because roughly 90% or so of the usual water in rivers all dried up - because the rain forest that had generated it before was gone.
In one of the Discworld Science books (I think) they said the best way to remove carbon would be to not to plant a forest, but to cut the forest down, and turn the trees that contain the carbon into books or asphalt (you can cycle on the roads if it makes you feel better, they quipped). A working forest means that some trees are decaying and releasing CO2, while others are growing up and fixing some CO2; but basically, a grown working forest is relativly neutral.
A newly planted and growing forest will bind some CO2; and forests are important for a lot of other reasons. But it’s not a magic solution to get all CO2 out of the air overnight. After all, all the CO2 currently in the air that mankind put there was sequestered by natural processes over millions of years; and we released in a couple of hundreds.
This is also a big concern for enviromentalists who see the big picture in regard to CO2 shares: you can make money planting a forest to sequester CO2 because of the shares - no matter if the trees are suited to the place where you are putting them (most likely third world countries, which are cheap and not in a position to protest), so you use fast-growing trees in a plantation; after about 10 years, you cut the trees down (fast-growing) and sell them for their wood (2nd time profit), and build a new forest (new profit from the share). Lather, rinse, repeat.
This fulfills the narrow goal of “sequestering CO2” and “making money”, but it doesn’t adress any of the other problems that deforestation causes, and it doesn’t give the people and the ecosystem nearby any of the advantages that a natural real forest has.