What if there were 1 trillion more trees?

At nearly 84 meters in height, the largest known living tree on our planet stands proudly, aptly nicknamed General Sherman. Over its estimated 2,500 years on Earth, this giant sequoia has performed a remarkable feat by sequestering approximately 1,400 tons of atmospheric carbon. While few trees can rival such an impressive carbon impact, the stark reality is that humanity now produces more than 1,400 tons of carbon emissions every single minute.

To tackle the pressing issue of climate change, we find ourselves faced with the urgent need to dramatically reduce fossil fuel emissions and actively draw down excess carbon dioxide (CO2) to restore the delicate balance of greenhouse gases in our atmosphere. But how exactly can trees contribute to this monumental fight, and what mechanisms enable them to sequester carbon in the first place?

Much like all plants, trees engage in the critical process of photosynthesis to absorb atmospheric carbon. During photosynthesis, these arboreal giants employ sunlight as their energy source to convert water and carbon dioxide into oxygen and energy-storing carbohydrates. Subsequently, in a process known as respiration, trees consume these carbohydrates, converting them into energy while releasing some carbon back into the atmosphere. Nevertheless, a significant portion of this carbon is not released; instead, it is stored within the newly formed wood tissue. Throughout their lifespans, trees effectively serve as carbon vaults, continually drawing down carbon as long as they continue to grow. However, when a tree eventually perishes and decomposes, a portion of its stored carbon is released back into the atmosphere. A substantial amount of CO2 is also stored in the soil, where it can remain sequestered for thousands of years. Yet, over time, even this stored carbon eventually returns to the atmosphere.

To make trees a meaningful part of the solution to the long-term issue of climate change, it is imperative that they survive to sequester carbon for the longest possible duration while also reproducing at a rapid pace. The notion of planting a single tree species that perfectly meets these criteria is a tempting one, but it doesn't align with the complex nature of forests and ecosystems. The most sustainable approach involves planting native tree species that naturally belong in their local environment. Preliminary research suggests that ecosystems with a diverse array of naturally occurring trees experience less competition for resources and exhibit better resilience in the face of climate change. Therefore, planting trees for carbon sequestration must be accompanied by a broader mission to restore depleted ecosystems.

There are numerous regions globally that have experienced clear-cutting or extensive development, which offer tremendous potential for restoration. A 2019 study led by Zurich's Crowtherlab used satellite imagery, combined with climate and soil data, to estimate that Earth could support nearly one billion hectares of additional forest, roughly equivalent to 1.2 trillion trees. This astonishing revelation captured the scientific community's attention and prompted further research. According to revised estimates, these restored ecosystems have the potential to capture between 100 and 200 billion tons of carbon, accounting for over one-sixth of humanity's carbon emissions. Astonishingly, more than half of the potential forest canopy suitable for new restoration efforts is concentrated in just six countries. This data also informs existing restoration initiatives like The Bonn Challenge, which aims to restore 350 million hectares of forest by 2030.

However, the complexities of ecosystem restoration present a significant challenge. Whether human intervention is the best approach for certain areas remains unclear, and there is concern that large-scale forest restoration could inadvertently lead to the production of natural bio-chemicals that accelerate climate change. Furthermore, even if we succeed in restoring these areas, future generations will need to safeguard them against the natural and economic forces that previously led to their depletion. These challenges have cast doubt on restoration projects worldwide, highlighting the importance of protecting our existing forests.

Nonetheless, the endeavor to restore depleted regions remains crucial, offering valuable data and bolstering our resolve to combat climate change on a larger scale. Should we succeed in these efforts, the modern trees we plant today may have the time and opportunity to grow into carbon-storing behemoths, contributing to a more sustainable and balanced world.