LEAF: A greenhouse gas drawdown champion

Years ago Paul Hawken, a well-known entrepreneur and environmentalist, noticed the lack of a comprehensive and doable list of solutions to global warming that is both clearly communicated and accessible to the general public. For example, we would hear “live closer to work,” “be more efficient,” or “consume less.” We knew those actions would help, but by how much, and what are the other things we could be doing? Hawken’s response in 2013 was to found with Amanda Joy Ravenhill a research non-profit called Project Drawdown with the goal of identifying, modeling, and communicating such solutions. As the name implies, the organization’s desired outcome is to reach a state of “drawdown” where atmospheric concentrations of greenhouse gases begin to decline over time, climate begins to stabilize, and we place our current civilizations and ecosystems on more stable foundations.

The initial work coordinated a group of over 200 researchers and experts from 22 countries to identify and model the top 100 solutions. During their review of hundreds of potential solutions, a particular solution rose to the top by being impactful (avoiding or sequestering at least 50 million tons of greenhouse gas emissions from 2020 through 2050), currently available or quickly scalable, economically viable, well-enough studied that data is available to model it at a global scale, and with benefits that outweigh side effects. Their findings are documented in the richly illustrated and readable 2017 New York Times bestseller “Drawdown: The Most Comprehensive Plan Ever Proposed to Reverse Global Warming.” A total of 80 solutions are measured by greenhouse gas impact, cost to implement, and savings accrued over the 2020-2050 time frame; 20 more promising solutions are listed but are too new to adequately measure, so no numbers are provided.

You might be pleased to know that the book reveals some good news: Under a conservative global implementation of the 80 solutions, we can reach a state of drawdown by 2060 while saving $47 trillion. Under the most aggressive implementation modeled, drawdown occurs as soon as 2045. The thoroughness of the solutions, the depth of research that went into quantifying them, and the criticality of addressing global warming have led me to personally deliver five workshops around Fremont introducing audiences to the project. All along, my hope has been that the work would inspire individuals, families, friends, and communities to adopt one or more solutions as their own.

What are the solutions? Fundamentally, they are practices which either prevent emissions of greenhouse gases into the atmosphere, or bring emissions already in the atmosphere back to earth in the form of soil carbon or mineral. Under the most conservative implementation scenario, the top 10 from highest to lowest impact are:

  1. Refrigerant management
  2. Onshore wind turbines
  3. Reduced food waste
  4. Plant-rich diet
  5. Tropical forest restoration
  6. Educating girls
  7. Family planning
  8. Solar farms (utility-scale solar photovoltaic power plants)
  9. Silvopasture (an ancient system of raising livestock in pastures containing live trees)
  10. Rooftop solar

In this blog post I want to focus on five solutions from the book that LEAF already is addressing through its two gardens, many workshops, and sale of seedlings to members and local retailers. The solution summaries are taken from the book’s text, and the emissions and financial numbers are from its conservative implementation scenario.

  1. Plant-rich diet (ranked #4): Various studies find that greenhouse gas emissions from raising livestock for their meat, eggs, and dairy are 15 to 50 percent of total emissions, much more than emissions from growing plant-based substitutes. Ruminant livestock, such as cows, goats, and sheep, are the greatest emitters, producing methane during digestion. But methane is not the only offender: Livestock-associated land use and the energy consumed during their rearing and processing emit carbon dioxide, and manure and fertilizers emit nitrous oxide. Beyond the climate impacts, there are tangible environmental impacts to the land cleared for pasture and waterways contaminated with runoff. Globally, this solution can reduce emissions by 66.1 gigatons by 2050.
  • Regenerative agriculture (ranked #11): This is a set of practices that prioritizes converting carbon in the atmosphere into organic matter in the soil, leading to improved water retention and nutrient availability, increased plant resistance to pests, and higher agricultural productivity. Tilling, plowing, pesticides, and externally-sourced nutrients (such as synthetic fertilizer) are avoided. Instead, in-farm fertility and pest control are encouraged through crop rotations and planting diverse cover crops and nitrogen-fixing plants alongside those that do not fix nitrogen. Conventional agriculture, in contrast, sees soil only as a medium to hold plants while water, fertilizers, and pesticides are brought in to meet their needs. Farms embracing regenerative practices see soil carbon increase 1-8% over 10 or more years, representing the addition of 25-60 tons of carbon per acre. Worldwide, the practice could sequester 23.2 gigatons by 2050, with a $1.9 trillion net return. As the book states, “Regenerative agriculture is one of the greatest opportunities to simultaneously address human, soil, and climate health, along with the financial well-being of farmers.”
  • Conservation agriculture (ranked #16): This practice involves three core principles: minimize soil disturbance, maintain soil cover, and manage crop rotation. In practical terms, farmers place seeds directly into the soil without tilling, protect the soil after harvesting by leaving behind plant residues or growing cover crops, and rotate crop locations to maintain soil fertility. It differs from regenerative agriculture in its use of synthetic fertilizers and pesticides, but is similar in that water and nutrients are retained in the soil. Farmers usually see costs drop while yields and income rise. Compared to regenerative practices, conservation does not sequester as much carbon (about 0.5 ton per acre), but nevertheless could make agriculture practiced in this way into a net carbon sink. As a bonus, increased water retention makes the soil drought resistant, and soil cover prevents erosion during heavy rains, providing protection from some of the weather patterns associated with global warming. Worldwide, the solution can reduce emissions by 17.4 gigatons by 2050, with a $2.1 trillion net return.
  • Composting (ranked #60): Modern centralized waste handling delivers much organic waste to landfills where it decays in the absence of oxygen, producing the potent greenhouse gas methane. Even though modern landfills attempt to manage the methane produced, with some burning it in engines to generate electricity, composting that same organic waste in a well-aerated process keeps the would-be methane as stable soil carbon. The carbon in compost becomes stable in the soil with the help of microbes (bacteria, fungi, protozoa), which in the process also make nutrients such as nitrogen, phosphorus, and potassium available to plant roots in exchange for carbohydrates from those roots in a symbiotic dance beneficial to both. Thus, keeping organics out of the landfill and applying the resulting compost to fields prevents emissions and returns valuable nutrients and fertility to farms. Globally, this solution can reduce emissions by 2.3 gigatons by 2050, with a $2.9 billion net return.
  • Farmland irrigation (ranked #67): This solution is not about whether one irrigates; it is about how. Irrigation for agriculture uses 70 percent of the world’s fresh water, and 40 percent of food production needs irrigation. Such vast water use inevitably depletes rivers and aquifers, leads to conflicts over water rights, and requires pumping with the associated greenhouse gas emissions from powering such pumps. Over most of human history, “flood” or “basin” irrigation has dominated, where fields are submerged in water diverted from various sources. Starting in the mid-1900s, people invented other methods (e.g. drip irrigation and sprinklers) which apply water where and to the extent needed. Although installing soil moisture sensors, timers, and rainwater/runoff catch basins add to capital costs, they can further improve water efficiency. Besides reducing energy needs for pumping, such practices improve yields, reduce soil erosion, cut down on pests (due to less humid fields), and decrease conflicts over water. The farmland area under drip and other “micro” irrigation has increased from 4 million to 26 million acres over the past 20 years, but still is less than 4 percent of global irrigated land. One of the main barriers to further adoption is the upfront cost of equipment and installation, especially in developing nations, but lower-cost technologies, loans, and subsidies are helping. Globally, this solution can reduce emissions by 1.3 gigatons by 2050, with a $213.5 billion net return.

Are you surprised LEAF has been a climate champion all along? I am not surprised at all: When we work to respect some things (e.g. our bodies with healthy food, our landscapes with sustainable gardening practices), we often respect other things in the process (e.g. the climate).

Can you implement any of these solutions in your own garden? Even if not, we should remember that the urgency and scale of global warming call each of us to quickly implement one or more solutions in our own special way. A climate-friendly garden is only one of many practices to reach drawdown, yet a profound one in that it sows seeds in others’ minds of how we can live with respect for ourselves and the natural world upon which we depend.

Jeff Goby is an analytical scientist in the bio-pharmaceutical industry and lives in Fremont. He has held a nearly lifelong interest in practices which sustain and regenerate environmental and human health, especially those which prevent or reverse global warming.

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