Trees are not enough

While recovering from a very minor surgery in hospital, I looked out over the top of a Jamun (Syzygium cumini) tree. Jamun is one of the fastest growing trees of India. In about 6-8 years it grows to a height of about 10 meters, and it lives for about a 100 years. It begins to fruit when it is about 8 years old, and continues to yield a good crop until it is well over 60. I love this fruit, and look forward to the hot time of the year for it. The tree is hardy and grows well enough to be considered invasive in some parts of the world. If you are interested in carbon mitigation through planting trees, this should be a great choice. But how much carbon does it bind?

A decade old tree is about a meter in perimeter, which means that with a height of 10 meters, its volume is 10/(4π) meter³, which is about 0.8 meter³. Jamun is one of the denser woods, with a specific gravity of 0.7. This means that a 10 meter tall tree weighs about half a metric ton. About half the weight of the wood would be carbon (the rest is essentially hydrogen, oxygen and nitrogen). Planting about twelve billion new jamun trees would be sufficient to capture the carbon that India emits in a year, for every year in the next decade or so.

Typically a jamun orchard will have a spacing of about 10 meters between trees. This means that one tree is usually planted in about 100 meter² of area, which is about 10,000 every km². India has an area of 3.2 million km². So planting enough Jamun trees to capture the carbon that we emit would take about 12% of India’s land area. This is a little larger than the area of France. However, this will have to be well drained loamy soil, with sufficient water. That would be about one fifth of the agricultural land in the country.

It already sounds pretty hard. But then I found that an increase in tree cover by 2261 kilometer² in two years was considered celebratory news. This, as you can see from the numbers above, is the area needed for about 0.02% (1 out of every 5000) of the trees one needs to plant! Maybe that means that planting enough trees to mitigate carbon emission is in the realm of pipe dreams. I’ve talked about a fast growing tree, because it would absorb carbon fast. If we take slower growing trees like teak or pine, then we would need to plant more of them to absorb carbon at the same rate.

Trees are good. Trees are healthy. Trees allow other vegetation to grow beneath it. Trees are needed to slowly suck the carbon out of the air. But today’s meditation convinces me that planting trees is no miracle cure to the climate change problem, no more than covering a pot while cooking is a solution. Pollution is a structural problem, and one needs structural changes for that. Making more efficient use of electricity is better. If I had another day in the hospital, I might have been able to calculate how much energy we can save my going off all social media altogether.

And since I’m joining in (against all good sense) to a challenge which asks us to show three photos, I must add that one should extend the title of this post and say that threes are not enough either.