Could Global CO2 Levels be Reduced by Planting Trees?

co2 levels planting trees

Could planting trees make enough difference to impact increased CO2 levels on a global level?

The idea seems simple enough. Since trees and plants "take in" carbon dioxide (CO2) during photosynthesis, planting more trees should reduce CO2 levels.

For reference, combined with oceans, the terrestrial biosphere including plants and trees already remove about 45% of the CO2 emitted by human activities each year.

Other scientists report that plants and trees globally are responding to elevated CO2 levels by taking up more CO2. 

This makes sense. Here at CO2Meter, our customers report to us that in controlled conditions like indoor greenhouses, doubling or tripling the CO2 levels can act as fertilizer, which increases the growth and productivity of plants.

Could enough trees be planted to impact CO2?

Unfortunately, not likely. Here's why.

A typical hardwood tree can absorb as much as 48 pounds of carbon dioxide per year. This means it will sequester approximately 1 ton of carbon dioxide by the time it reaches 40 years old. 

One ton of CO2 is a lot. However, on average human activity puts about 40 billion tons of CO2 into the air each year. This means we would theoretically have to plant 40 billion trees every year, then wait for decades to see any positive effect. By the time 40 years had passed, the trees we had originally planted would only cancel out the increased CO2 levels today.

But others disagree.

For example, National Geographic says "An area the size of the United States could be restored as forests, with the potential of erasing nearly 100 years of carbon emissions." This is based off of the first study of its kind to determine how many trees the earth could actually support.

The other issue is the impact of CO2 on tree growth and the species of trees that thrive best on high CO2 levels.

For example, research from NASA indicates that the current increase in CO2 levels have resulted in a significant greening increase over the last 35 years. This increase in leaves on plants and trees is actually equivalent to planting a forest twice the size of the continental United States. Yet, the shorter lifespans of these trees as the result of faster growth give them less time to absorb CO2 than was anticipated. This implies that the trees will die sooner and before they're big enough to store a significant amount of carbon from our atmosphere. 

So should we really continue to plant trees?

Science Magazine published a report titled, "The global tree restoration potential" which concluded that there may seem to be enough land to increase the worlds forest areas by approximately one third. The downside to this is that the potential for land space can diminish quite quickly given global temperature rising. Additionally the report states, "Even if global warming is limited to 1.5 degrees Celsius, the area available for forest restoration could be reduced by a fifth by 2050 because it would be too warm for some tropical forests." 

This same topic was researched in 2016, where a research group of 800,000 volunteers in India planted 50 million tree saplings in an effort to re-green the country. While there are many good reasons to combat deforestation, this project would have to be replicated 800 times to cancel out the CO2 created by humans.

This does not mean that there is still not some importance in doing so, however. Global CO2 levels could be reduced by planting trees as national geographic concludes, "If we act now we could cut carbon dioxide emissions by at least 25% these levels would not have been seen until almost a century ago". 

Aren't loggers required to replace the trees they cut down?

In many countries there are regulations that require logging companies to replace the trees they log. According to "Three quarters of all the trees planted in America last year were planted by forest product companies and private timberland owners. And logging companies pay a special fee to fund for replanting and reforestation when they buy the right to harvest a section of timber on state or national forests." Americans plant at least 1.6 billion trees or about 6 trees for each one we use. 

However, the same philosophy of forest management is not occurring in other countries. While their are conflicting data sets as to the rate of deforestation, all scientists agree that we are continuing to have a net loss of forests year after year. According to the Food and Agricultural Organization of the United Nations:

"Between 2015 and 2020, the rate of deforestation was estimated at 10 million hectares (38,000 square miles) per year, down from 16 million hectares per year in the 1990s. The area of primary forest worldwide has decreased by over 80 million hectares 310,000 square miles) since 1990."

For example, more than half the potential to restore trees can be found in the following countries: Russia (373 million); Canada (78 million); Australia (58 million); Brazil (50 million); and China (40 million).

So the answer seems to be that planting trees, while a good idea, would not in itself cancel all of the effects of human production of CO2 and many trees would actually die off before they are large enough.

For more information on deforestation visit the State of Forests and Forestry website.

What is the best way to offset CO2 levels?

While planting trees are important, trees alone aren't enough. As a single person, what can you do to help offset the rise in CO2 levels?

1. Reforestation. If you own land, plant trees on it. As the old Chinese proverb goes, "The best time to plant a tree was 20 years ago. The second best time is now.” Here are the trees that convert the most CO2:

2. Renewable energy. There are dozen's of small ways you can take advantage of renewable energy around your home, from solar panels to roof-mounted solar water heaters to paying a few dollars extra to the utility company each month for their carbon offset program. Building a new house? Talk to your architect about using thermal mass walls to retain both heating and cooling.

3. Community projects are a great way to get involved and help the climate. The advantage of these projects is that you will spend time with like-minded people and see for yourself what works and what doesn't in their homes and businesses.

4. Waste to energy initiatives are programs that convert organic waste into energy. The only way these can happen is by supporting government officials and politicians who are also committed to these goals.

5. Changing transport. Common sense says that taking a train instead of a plane doesn't matter since the plane would make the trip with or without you. However, for personal transport, electric cars finally make sense. If everything you know about electric cars is over a year old, it's time to research them again.

We can take steps to reduce CO2 emissions now, or we can wait and see what happens. Only good science and good data will give us a valid answer.

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