If planting trees is ineffective to tackle climate change, why do people plant them?

Question

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?

Answer 1

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.

Answer 2

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.

Answer 3

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.

Answer 4

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

Answer 5

There have been Carbon Offset schemes by some nations, that pay for tree planting (or in some cases pay for not cutting down trees) in place of actual emissions reductions.

The politics around these can get murky with respect to motivations ("why") but include both sincere efforts to make these work as one element of an emissions reduction policy - usually as a kind of stopgap action to give time for new investments in low emissions energy to flow through - as well as insincere efforts, to appear pro-active whilst not requiring substantive change to emitting industries. Or even to cash in on emissions reduction funding and/or funnel it inappropriately as political favors.

Because the climate issue had initially been widely framed as environmental and fringe rather than economic and mainstream it had been seen widely as driven by environmentalists who have long opposed land clearing and promoted re-forestation. Some of these schemes appear to have been developed by environmentalists and some to appease Environmentalists (and an increasing concerned public) who promote tree planting as a simple and environmentally beneficial act irrespective of climate change.

The climate problem has increasingly become seen as economic and mainstream over time and the effectiveness of reforestation as Carbon Offsets faces ongoing scrutiny, including by "green" political parties and others concerned with "greenwashing" (the contrived appearance of supporting emissions reductions goals whilst avoiding emissions reductions.

Answer 6

Trees do not trap only CO2, they trap water and water vapour is a major contributor to climate change. In any case the research you cited is purely theoretical because the current growth of existing and newly planted trees is not enough to offset the quantity of trees that we are cutting down.

Other points:

• the research you cited does not take into account the impact that forested areas have on rain cycles.
• the research you cited assumes that all desert areas are covered by highly reflective quartz sand. But even in the Sahara you can find dark rocky landscapes that trap a lot of heat.

Answer 7

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.