As you may be aware, trees mitigate carbon dioxide, a major greenhouse gas. As such, tree planting has gained popularity as a form of carbon offset, with some cities and states providing incentives to plant trees as an offset activity.
This 2015 study of the Twin Cities suggests that trees can help, but that they also offset a minor amount of carbon emissions. In other words: Trees help, but as a policy tree planting must be accompanied by aggressive tactics to reduce the emissions to be offset.
Researchers calculated the amount of carbon generated in Ramsey County and Dakota County, and then calculated the amount of carbon absorbed by all trees in those counties. They found that trees offset just 1% of these counties’ carbon emissions. They also noted hotspots – shown in red on the map – where the amount of carbon generated was high and the number of trees was low. The land area represented in the study is roughly 331 square miles, with a population (in 2015) of more than 350,000 people. Researchers calculated carbon emissions per census block — land areas with populations of at least 2,500 people that are used by the US Census.
While researchers found that trees were inadequate to the emissions produced, they do emphasize that trees are still beneficial as part of an overall climate approach, as well as lovely, scenic, shade-giving and positive for the environment.