he devastating impact of climate change is an unfathomable prospect that will pervade current and future generations. Despite enormous global awareness, there remains no clear-cut, realistic, and tangible climate change solution. Government officials, activists, and scientists propose numerous changes for reducing carbon emissions. The proposals range from effective refrigeration management, with the potential to save ~24 billion tons—that is about 65,000 Empire State Buildings—of future carbon emissions to adopting a plant-only diet—a measure that could save approximately ~18 billion tons of future carbon emissions.

Restoring Natural Ecosystems

Behavioral and technological changes are all vitally important for addressing climate change, but if we want to substantially reduce our current trajectory—capturing in excess of 300 billion tons of atmospheric carbon that already exists—we need a more powerful and comprehensive approach. Recently, a number of technological solutions and geoengineering strategies—such as Direct Air Capture (i.e., scrubbing CO2 out of the atmosphere)—have emerged that show some promise for capturing existing carbon. Ultimately, we will need to use many of these approaches in combination to significantly drawdown the current level of atmospheric carbon.

Restoring natural ecosystems is one solution often talked about, but rarely given any serious consideration as a viable approach. Die-hard environmentalists often view ecosystem restoration as a somewhat “feel-good” endeavor—a futile response to deforestation. The stigma surrounding forest restoration persists for the simple reason that we lacked quantitative global information about the current state of the world’s ecosystems. Questions such as, “How much carbon do the world’s forests currently store?” and “What is the future carbon storage potential of forests?” left researchers and policy makers with little more than conjecture. Without comprehensive data, it has been impossible to benchmark the value of forest or ecosystem restoration as a valid climate-change solution.

A Big-Data Approach

Until recently, our understanding of global ecosystems stemmed only from satellites. Satellites provide amazing global coverage of forests, but they do not tell us about the plants and microorganisms that form the structure and basis for ecosystems below the canopy. To address this challenge, researchers in the Crowther Lab at ETH Zurich - have begun to develop and implement new approaches for generating quantitative information about the current and potential carbon storage of global ecosystems. By establishing massive international networks of ecologists and pooling data from millions of on-the-ground measurements of local ecosystems, we can now build machine-learning models to map the distribution of microorganisms across the globe.

This big-data approach has already revolutionized our understanding of the terrestrial biosphere, illustrating the staggering scope and complexity of the world’s forests. We have revealed that there are just over 3 trillion trees on the planet - more than there are stars in the Milky Way galaxy. More importantly, we can now identify where forests could exist across the globe, demonstrating that there is room for an additional 0.9 billion hectares of forest. Restoring these areas would capture 205 billion tons of carbon from the atmosphere, two-thirds of the global atmospheric carbon burden - simply by reforesting natural ecosystems. Following this information, the United Nation’s ‘billion-tree campaign’ has been scaled to the ‘trillion-tree campaign,’ and a large network of restoration organizations are using the global maps generated by this research as guidelines for optimizing and targeting their planting effort.

Researchers in the Crowther Lab, along with others across the globe, continue to build on the data. The information that the data provides gives us a comprehensive, quantitative, and holistic understanding of the carbon-capture benefits of forest restoration. Indeed, tree planting is just the tip of the iceberg. In order to understand the health of ecosystems across the globe, we need to understand the soil beneath our feet. Soil serves, at least for now, as the largest terrestrial carbon stock across the globe. We are using the same big-data approach to quantify the composition and health of forest soils, and to assess the carbon-storage potential of other ecosystems, such as grasslands and savannas. This work reveals that the carbon-capture potential of ecosystems is not limited to trees and that combined, restoration of natural ecosystems to their native states has the potential to capture the majority of human-derived atmospheric carbon.

A Comprehensive Climate Solution

As a low-tech, low cost solution, global ecosystem restoration is among our most powerful tools in the fight against climate change. It took a unique, holistic approach, as well as a collaboration with hundreds of researchers from around the world to map out this solution. The global-scale of this research transforms our understanding of the biosphere, providing a realistic climate change solution that each of us can implement immediately.

What makes this solution so revolutionary is that it does not depend on new technologies, and it does not rely on governmental policies that can oscillate over time. In fact, it is a truly democratic solution, one in which potentially everyone on the planet could participate. Depending on each an individual’s level of support and commitment, each one of us could get involved by:

• Volunteering to planting trees directly with local restoration groups,

• Donating money for restoration projects, or

• Simply investing wisely and buying goods from environmentally responsible organizations.

Like most climate change solutions, engaging people around the world remains the only and most significant hurdle. Unlike all of the current climate change solutions, we do not need to wait around for politicians and governments to make it happen.

Editor's Note: For consistency, all CO2 figures have been converted to carbon. Forty-four grams of CO2 has approximately 12 grams of carbon.
Thomas Crowther
Thomas Crowther is a professor of Global Ecosystem Ecology at ETH Zurich where he founded the Crowther Lab. His multidisciplinary team works with the world’s largest set of ground-sourced data creating a holistic view of forest ecosystems and their capacity to store carbon.
The views presented in this article are the author’s own and do not necessarily represent the views of any other organization.