Recently, a study was published that found that we had room to plant a trillion trees and that it would do some good for global warming. Naturally, it garnered a lot of the usual adulatory headlines and the reporting didn’t put a lot of context on the results.
- Washington Post: Want to stop climate change? Start by planting a trillion trees.
- Time: Planting a Trillion Trees May Be the Best Way to Fight Climate Change, Study Says
- Bloomberg: Plant a Trillion Trees, But Don’t Stop There
- CBC: Planting 1 trillion trees could slow climate change. Here’s how Canada could contribute
- CleanTechnica: Got An Overheating Planet? Plant 1 Trillion Trees. Problem Solved
Yes, even CleanTechnica got in on the enthusiastic reporting. But as always, the underlying numbers need assessment and we have to look at the ability to scale the solution.
Obviously, not every place in the world is suitable for planting trees. The study in question, The global tree restoration potential, published in the journal Science in July 2019, established the potential for every place on Earth for new forests. The authors found that planting a trillion trees would basically help with the last 25 years of emissions. That’s pretty good, but we have been emitting CO2 since about 1760 in increasing amounts, and we are continuing to emit CO2 at a greater rate each year.
Let’s put the trillion trees into context.
There are already about 3 trillion trees on the planet, per a 2015 study, Mapping tree density at a global scale, published in the journal Nature with overlapping authors. Another trillion is full third increase. Given deforestation over the past few thousand years, this is not as big as you might thing. The study says 15.3 billion trees are chopped down every year and estimates that 46% of the world’s trees have been cleared over the past 12,000 years. Yeah, the 3 trillion used to be closer to 6 trillion.
In more context, the New Zealand government has committed to planting a billion trees in that country alone. It’s a rich enough country per capita, but its GDP places it in 51st position. It’s only the 75th largest country in the world. If New Zealand can commit to a billion, that’s not bad. But it’s also not good. It’s the 25th richest country by GDP per capita, a useful measure, and is only committing 1/1000th of the number of trees required.
China is also worth assessing. It’s the second biggest country by GDP and 3rd largest by size. It has the most aggressive reforestation campaign in the world per the UN.
As the World Economic Forum points out:
China plans to grow 6.66 million hectares of new forest this year, having already created 33.8 million hectares (338,000 square kilometres) of forest in the past five years, says Zhang Jianlong, head of the State Forestry Administration, in a report from Reuters. The country wants to increase the area of land covered by woodlands from 21.7% in 2016 to 23% by 2020, according to China Daily.
As the graph shows, China has been planting trees rapidly since 1990 to reforest a land stripped bare by subsistence farming, which outside of beef and palm oil, is the worst thing for deforestation going.
China never does anything for a single reason, and it isn’t replanting trees just for global warming. Trees are also a major factor in reducing air pollution, and that’s been a huge issue internally to China for a couple of decades. They artificially cleared up the air of Beijing for the Olympics in 2008, but that was a temporary two-week lull in some of the most polluted air on the planet. Now Chinese cities are seeing much improved air, still worse than North American and European standards, but well above Indian standards right now. And to be clear, Europe and North America had similar air quality problems only a few decades ago. The air used to kill people regularly in New York and London.
China is serious enough that it pulled 60,000 soldiers off of military duty to plant trees in 2018. That’s only about 2% of its military, but it is still a huge number. That’s more military people than about 140 countries in the world have in total.
As the graph shows however, China has only increased its forest cover by a third in close to 25 years. I looked up the average trees per square kilometer recently for a different exercise, The Best Trees To Plant For Global Warming Have Three Blades & Generate Electricity, and it’s about 75,000 per square kilometer.
China has put about 510,000 square kilometers under forest cover since 1990. It’s a monoculture, so it’s not as good as a normal forest for some things, but it counts for global warming. That turns into about 38 billion trees that China has planted.
China, which has been aggressively planting trees for close to 30 years, has more people than any other country, is the second richest country in the world and the 3rd largest country in the world by land mass, has only managed to plant about 4% of the required trillion trees.
That isn’t a rapid solution or one that will be replicated in the much less wealthy and much smaller countries in the world. For one thing, we need to do a lot more in the next 11 years. For another thing, China is able to reforest because it made itself rich.
What’s this a picture of? Well, it’s a picture of the border of Haiti and the Dominican Republic in the Caribbean. The side without any trees is Haiti. The Dominican Republic has the 66th largest GDP in the world. Haiti has the 139th largest. Haiti is dirt poor due to a long series of incredibly poor luck between corruption, horrible leaders, and natural disasters. And there are 60 countries poorer than Haiti.
If, as one example, the richest country in the world and the one responsible for vastly more of the greenhouse gas emissions since the Industrial Revolution than any other country, and in fact all 28 countries of the EU, were to be signatory to the Paris Accord, then funding would be available to poor countries to help them reforest.
But the USA walked away from the Paris Accords after Trump was elected.
All of this is to say that we aren’t going to get anywhere near a trillion trees planted in anywhere near enough time. Every tree planted is great, but basically we might hit 10% of the trillion in a decade with a global moonshot program. A hundred billion trees is good, it buys us some time and it’s a good thing to do, but if we don’t stop emitting CO2, then we aren’t going to win the battle.
And as my calculation on wind turbines vs trees show, putting in wind turbines is 8x as effective at annual CO2 emissions reductions as planting trees in the same area, provides very useful and profitable electricity every year, and unlike trees, doesn’t return much of the CO2 to the atmosphere when they are taken down. Wind and solar farms permanently remove CO2 from the air in larger volumes than trees do.
This means we should be doing both, but not believing that trees are a magic bullet. We need a lot of solutions to get over the line.