California Urban Area Requires No Tree


According to San Jose’s official report, “There are approximately 1.6 million trees in San Jose’s entire urban forest (street trees and all trees on public and private land). San Jose’s urban forest produces ecosystem services valued at $239.3 million annually.”

However, after close examination, I found this is completely bullshit. San Jose and probably other California urban areas require no tree at all. In this blog post, I would like to discuss why this is the case.

Leaf Blower Emissions

Despite the fact that leaf blowers produce extremely heavy contaminants to the nature, San Jose, as well as other California urban areas, use leaf blowers a lot everywhere and everyday. The rate a leaf blower produces gas contaminants, including non-methane hydrocarbons, oxides of nitrogen, carbon monoxide, can be even 300 times higher than a 2011 Ford Raptor can produce. In addition to these gas contaminants, it produces a significant amount of carbon dioxides. According to the “Gas Powered Leaf Blower Noise and Emissions Factsheet”, backpack style leaf blower can produce 11 pounds of CO2 per hour of use.

The leaf blowers usually work 8 hours a day and 365 days a year. The fallen leaves of every tree have to be blown every week. This is because California city governments do not allow fallen leaves on the ground. So it’s not surprising to see them anywhere at anytime, even if it’s in winter when there is almost no fallen leaves on the ground.

Based on my observation, the leaf blower efficiency is extremely low. One leaf blower usually can only clean an area that has no more than 20 trees in 2 hours. This translates to 80 trees in a day assuming 8 hours of work per day, and 560 trees in a week assuming the leaf blower never take rest. This means, San Jose has at least $\frac{1.6 \times 10^6}{560} = 2857$ leaf blowers working everyday in different area of the city everyday.

In San Jose, the total CO2 emissions from these leaf blowers are $2857 \times 8 \times 365 \times 11 = 9.2 \times 10^7$ pounds per year!

Tree Economics

In our tree economics, we will ignore the facts such as the impact of one pound of nitrous oxide on warming the atmosphere is almost 300 times that of an equivalent pound of carbon dioxide, and only consider the carbon dioxides emission from leaf blowers.

According to the Arbor Day Foundation, in one year a mature tree will absorb more than 48 pounds of carbon dioxide from the atmosphere and release oxygen in exchange.

As mentioned before, San Jose urban area has 1.6 million trees. This means all the trees in San Jose urban area can absorb $1.6 \times 10^6 \times 48 = 7.7 \times 10^7$ pounds of CO2 per year.

This means, even if we only consider the CO2 emissions from the leaf blowers, the CO2 emissions are already higher than all the trees can absorb in San Jose. The $239.3 million ecosystem service value is completely bullshit! Not to mention spending hundreds of millions of dollars on leaf blowers.

If there were no trees in San Jose urban area, we would not require leaf blowers and we would emit less CO2. That’s why I said “California urban area requires no tree”.

Tree Economics Calculator

We could use the following calculator to calculate the tree economics coefficient.

The tree economics coefficient is defined as the ratio of the CO2 absorption of all the trees in the urban area to the CO2 emission of all the leaf blowers in the urban area.

If the tree economics coefficient is less than 1.0, the city requires no tree. Only if the tree economics coefficient is much greater than 1.0, the city might consider having trees.

Tree Economics Coefficient

Please input the following parameters to calculate the tree economics coefficient.

Number of Leaf Blowers

Sometimes we don’t know exactly the number of leaf blowers working in the city on the same day. But we could estimate it using our observations.


California urban area requires no tree, because the leaf blowers produces much more CO2 than the trees can absorb.

Before creating any policy, please do some elementary math first.



Lei Mao

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