We have heard that planting trees – reforestation and afforestation – can control the adverse effects of climate change. Reforestation refers to replanting trees in a forest after a fire, development, and so on. Afforestation is the process of planting trees in the areas that were not previously forested. Trees inhale carbon dioxide, store it, and convert it to carbohydrates. Therefore, trees are natural carbon sinks. There are many campaigns to plant trees to mitigate climate change e.g. the campaign led by Greta Thunberg, Plant a billion trees, and Green belt movement, just to name some. Even some governments and jurisdictions support these campaigns. The UK has planted millions of trees recently, planning to plant another million until 2024. Besides climate change control, planting trees improves landscapes and biodiversity.
Recently, there have been arguments about the efficiency of planting trees to fight the climate crisis. In 2017, deforestation contributed to 10% of total emissions. Once a tree falls, all carbon stored in leaves is sent back to the atmosphere. Therefore, perhaps, stopping deforestation is a more efficient way to mitigate climate change rather than reforestation. Another argument is the net effect of trees. Trees are dark objects, at least compared to grass. We know that dark objects tend to absorb heat rather than giving off. Replacing bright lands, e.g. grasslands or snowy areas with forests could harm the environment by absorbing more heat. Therefore, selecting the reforestation sites should be a careful process. One more recent question that was brought into attention by the researchers of the University of Leeds, was about the maximum capacity of the Earth for afforestation and reforestation. When we walk in the woods, we sense the pleasant and natural smell that comes from the trees. This is, in fact, chemical aerosols that are suspended in the air. These particles react with the other particles including greenhouse gas particles to even intensify climate change. The net result might not be what we expect from the forests. Therefore, there should be a fine balance in the afforestation process.
As we see, there seem to be lots of questions and uncertainties in planting trees. To be efficient, it has to be done right. But this is not the main concern! The main concern is social and political inconsistencies and uncertainties. In many regions, e.g. the Welsh hills, the deforested land is occupied by industries such as farmers. It is hardly possible to relocate residents and plant trees in those lands. This problem can be found almost everywhere. Free idle lands ready to be forested are not available, and therefore, policies are required in addition to community engagements for afforestation in the right place with the right intensity.
All these uncertainties and challenges do not change the bottom line: climate change is a crisis. There are various ways to mitigate it, and one powerful solution is afforestation and reforestation. All possible ways including these two should be implemented with the recommendation of experts rather than sporadic unstudied actions. A synergy between governments (at different levels), experts, and residents can certainly reduce the adverse effects of climate change. It is time to ask for this synergy as we plan to recover and to build a better society after COVID-19.
- K. Sporre et al., 2019. BVOC–aerosol–climate feedbacks investigated using NorESM. Atmospheric Chemistry and Physics Volume 19.
- Bala et al., 2007. Combined climate and carbon-cycle effects of large-scale deforestation. PNAS Volume 104