How Many Trees Needed to Offset Your Carbon Emissions?

How Many Trees Needed to Offset Your Carbon Emissions?
Many people wonder, how many trees are needed to offset carbon emissions?
On average, each person in the US releases about 16.5 tons of carbon dioxide (CO2) each year, a quantity equivalent to the emissions from about 46 barrels of oil or approximately 22,046 pounds of coal, making the carbon footprint per person in the US one of the highest in the world.7
Fortunately, to minimize the adverse effects of these greenhouse gas (GHG) emissions, US citizens are taking active steps to reduce their carbon footprint.
Keep reading to learn how…
How Trees Offset Carbon Emissions
Forestry offset programs are one of the tactics adopted by some to offset their emissions. Unfortunately, most people are unaware of the number of trees they need to plant to offset their emissions. The process of computing the number of trees required to offset the emissions from each person is fairly complex, and online carbon footprint calculators from reputable sources offer the best bet for obtaining accurate estimates.
Nevertheless, given a single tree offsets about 20 kg (44 pounds) of carbon dioxide each year, individuals in the US emitting 17 tons of emissions will need to plant about 500 trees each year, to successfully offset their carbon footprint.14
This figure varies based on a host of contextual factors, including the region where the trees are planted and the exact ecosystems of the location. Trees planted in the tropical and subtropical regions tend to sequester more carbon dioxide than those planted in other regions.
In contrast, trees planted in marshlands and wetlands offer the highest sequestration volumes of all other ecosystems.
Trees play a vital role in offsetting carbon dioxide from the atmosphere, but what exactly do they do?
The Carbon Cycle
To understand the importance of trees, one has to begin by looking at the carbon cycle.
The term “carbon cycle” refers to the process through which carbon atoms move from the earth’s surface to the atmosphere, and vice versa.13 Within the cycle, oceans, sediments, rocks, and living organisms on the earth’s surface are the main carbon storages.
The carbon stored in oceans is released into the atmosphere through a continuous exchange process between the ocean waters and the earth’s atmosphere.9 Soil-based carbon is released in a different process, when organisms die or in instances when sediments and rocks are degraded.
Role of Trees in the Carbon Cycle
Degraded or deforested lands release significant volumes of carbon in the atmosphere and are driven mainly by human activities, such as poor agricultural practices and human-induced soil erosion.
Trees remove carbon emissions by storing them for a long, long time, effectively removing them from the atmosphere.
You can calculate how many trees you’d need to need to offset you emissions using this tree calculator. Simply increase the number of trees (or the age and circumference of the tree) to see it’s equivalent in carbon emissions.
Other human carbon sources that release GHG emissions into the atmosphere include:
coal mines
gasoline vehicles
carbon-based industrial activities
The role of trees in the carbon cycle is to remove carbon from the atmosphere by restoring it into the soil- a process called carbon sequestration.13 The trees do this through photosynthesis, where they extract carbon dioxide from the atmosphere and use it to make their food. Carbon sequestered in this manner is stored as biomass in the trees, or biowaste in the soil.
Statistics on The Role of Trees in Carbon Sequestration
The following statistics illustrate the importance of trees in offsetting carbon emissions:1
As of 2018, old forested lands in the US sequestered about 644 million tons of equivalent carbon dioxide emissions, while new lands converted into forests created carbon sinks that eliminated 111 tons of equivalent carbon dioxide emissions
Between 2018 and 1990, the US experienced a forest cover reduction of 2.7 million acres.
The above statistics imply that old and new forested lands combined remove carbon emissions similar to those released by about 190 coal-fired plants.3
The potential for emission offsetting with trees is also relatively high, considering an additional 100 acres of forest can remove 115 tons of carbon dioxide per year.1 Unfortunately, the US may be unable to sustain these gains considering that the nation’s forested land is declining, as indicated by a 2.7 million reduction in forested acreage between 2018 and 1990.
Given that these trends are likely also happening in other parts of the world, climate change practitioners need to initiate quick actions to increase forest cover both locally and abroad.
One way to do this is by engaging in large-scale and small-scale tree planting projects in areas that promise the highest impact—some of the areas include tropical, sub-tropical regions, and wetlands.
Number of Trees to Offset Emissions in Tropical and Subtropical Regions
While, on average, trees across the globe offset about 44 pounds of carbon dioxide each year, the figure is slightly higher for tropical trees for two main reasons.14
Why Tropical and Subtropical Trees Sequester More Carbon Dioxide
First, trees within the tropics grow faster than other regions of the globe, implying a faster pace of sequestering carbon back into the soil.
These unique attributes of tropical forests make them highly suitable for conducting large-scale reforestation efforts to combat climate change. To offset a specified volume of emissions, one is likely to plant fewer trees in the tropics compared to other regions of the world.
Unique Attributes of Tropical and Subtropical Lands
The tropical and subtropical regions are sections of the earth between the Tropic of Cancer and Capricorn latitudes.
Given the position of these latitudes, tropical regions are located at roughly the middle sections of the earth, accounting for 36 percent of the earth’s landmass, and hosting a third of the global population.8
Temperatures within the tropics range between 77 and 82 degrees Fahrenheit (25 and 28 degrees Celsius), largely due to the all-year-round sun exposure experienced in the region. Rainfall in regions experiences a much wider variation, with some areas receiving as much as 4,000 mm per year, while others receive as little as 500 mm.12 Due to the huge climatic and ecosystem similarities in the tropics, the regions have similar animal and trees species.
Statistics on the Role of Tropical Lands in Carbon Sequestration
The value of the tropics in carbon offsetting is clear, especially when one takes a global outlook perspective.
Based on current information from the Global Forest Watch Climate, if current trends of loss in tree cover within the tropics continues, it will be impossible to keep global warming to within a 2-point degree, as envisioned by the prevailing climate change agreements.5
Yearly carbon dioxide emissions from tree cover losses within the tropics were about 4.8 gigatons between 2015 and 2017.
The figure is 63 percent higher than the previous 14 years combined
Tropical trees can offset about 23 percent of total global emissions
From the numbers, it’s clear that tropical tree covers are reducing, with devastating effects to the planet. For perspective, the 4.8 gigatons of emissions released from the reduction in tropical tree cover are equivalent to emissions from 85 million gasoline cars over their entire life cycle.3
More importantly, reforesting tropical trees is likely to contribute immensely to reducing CO2 emission globally, considering that tropical trees can reduce about a fifth of global emissions.
Important to note, however, is that the ability of tropical trees to sequester carbon dioxide from the atmosphere is not infinite.
Researchers note that if global warming increases to 2 degrees Celsius above pre-industrial limits, tropical trees will lose more carbon than they can accumulate.
Sadly, some of the hottest forests in South America have reached this tipping point, where they emit more carbon than they store. This trend calls for quick action to reverse the devastation by planting more trees in tropical regions such as the Amazon rainforest.
The Number of Trees to Offset Emissions in Wetlands
Trees grown in wetlands tend to sequester more carbon dioxide than those planted in other regions of the globe. Granted that, on average, trees sequester about 44 pounds of carbon dioxide, the figure for wetlands is likely higher than this for two main reasons.
Why Wetlands Sequester More Carbon Dioxide
First, wetlands in general are oxygen-starved, as most of the soils are submerged. Thus, the decomposition rate in the regions is much slower than in other parts of the globe, leading to a higher accumulation of organic matter.
Secondly, many wetlands reduce erosion by trapping soils, so more carbon is stored within the soil sediments. These factors lead to higher sequestration volumes, implying for a specified volume of emissions, one is likely to plant fewer trees in wetlands compared to other regions.
Unique Attributes of Wetlands
Wetlands refer to areas where the soil is submerged in water either throughout the year or during specific seasons.
Most wetlands on earth are found within the tropics, with every continent except Antarctica having some form of wetlands. Generally, wetlands are classified into coastal and inland wetlands.4
The former comprises wetlands within coastal regions. They are mostly found at estuaries, where seawater meets the land. On the other hand, inland wetlands are located away from coastal areas along rivers, in isolated depressions or, in some cases, in low-lying areas where groundwater flows to the surface.
Statistics on the Role of Wetlands in Carbon Sequestration
Trees in wetlands sequester carbon dioxide into the soil in two main ways, namely photosynthesis and sediment trapping.
Through photosynthesis, the trees convert carbon dioxide into biomass and biowaste, sequestering carbon back into the earth in the process. The biomass is stored as food or biomaterial within the trees, while biowaste is released into the ground as litter, organic matter, or peats.
The following statistics indicate the importance of wetlands in carbon sequestration:
Wetlands in the US store about 15 billion tons of carbon dioxide yearly.2
A 0.09 to 0.88 meter rise in sea level due to global warming will likely reduce the area of coastal wetlands.6
A temperature rise of 2-9 degrees Fahrenheit is likely to adversely affect flora and fauna of most wetlands.6
Notably, wetlands play a crucial role in carbon offsetting.
The 15 billion carbon sink provided by wetlands sequesters about 55 tons of carbon dioxide from the atmosphere, a figure equivalent to the emissions from about 23 tons of burned coal.3
Unfortunately, as the effects of global warming take root, the carbon sinks provided by wetlands are likely to reduce. Specifically, increased sea levels and global warming will likely have devastating effects on wetlands. This point is important to note- just like tropical trees, the sequestration potential of wetlands is not infinite.
While wetlands are some of the largest carbon stores globally, their disruption is likely to increase the volume of emissions they generate, to a point where they are more than carbon dioxide sequestered back into the soil.
This point is particularly true, considering wetlands are also the most significant global sources of methane, another harmful greenhouse gas, with 100 times more potency than carbon dioxide.10 According to the Minnesota Pollution Control Agency, methane emissions are highest in inundated wetlands, necessitating actions to protect such wetlands, so that the methane is not released into the atmosphere.2
Some of the effective interventions include:
stopping the draining of wetlands
controlling wetland fires
restoring or reforesting the locations
Using Trees to Offset Your Carbon Emissions
US Citizens are among the largest global emitters of greenhouse gases, with each individual in the nation releasing about 22,046 pounds of CO2 into the atmosphere.7
To offset this massive volume of emissions, each person in the country would need to plant about 150-200 trees (depending on the species) every year. Individuals keen on offsetting their emissions should consider reforestation in areas with the highest impact for best results.
Tropical and subtropical regions are one such area that has immense potential to offset emissions compared to other parts of the globe. The trees in this region grow faster than other places, and, in the process, they release more biomass into the soil, sequestering higher volumes of carbon dioxide.
Planting trees in these regions is likely to deliver excellent results, considering that tropical and subtropical regions have the potential of offsetting 23 percent of global emissions.5
This potential is not infinite, though, considering trees can emit more than they offset at high global temperatures. Some trees in the South American tropics have reached this tipping point, thanks to the steady rise in global warming over the years.11 So, it’s wise to act fast, before climate change takes away one of the best options for mitigating it.
Wetlands are another area with immense offsetting potential, due to the slow decomposition in the region, leading to higher organic matter accumulation and the carbon trapping ability of the wetland soil. Planting trees to rehabilitate wetlands is necessary, considering that they will emit more than they offset without such efforts.
If disturbed, these regions are likely to release more methane into the atmosphere than the carbon dioxide they extract from the environment.
All in all, reforestation initiatives in tropical regions and wetlands are exceedingly important in attempts to combat climate change, especially considering these regions sequester more carbon dioxide than other parts of the globe.
9National Ocean’s Service. (2021). What is the carbon cycle? From National Oceanic and Atmospheric Administration U.S. Department of Justice: https://oceanservice.noaa.gov/facts/carbon-cycle.html
10Pearce, F. (n.d.). Scientists Zero in on Trees as a Surprisingly Large Source of Methane. Retrieved August 8, 2021 from YaleEnvironment360: https://e360.yale.edu/features/scientists-probe-the-surprising-role-of-trees-in-methane-emissions
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