We posit that a reversal of the growth of atmospheric carbon dioxide and other greenhouse gases is feasible using a socially responsible, economically productive and ecologically restorative agroforestry system we call "Climate Ecoforestry." This system, if carried to the scale of 50 Mha/yr, could annually sequester enough carbon from atmosphere to soils and living biomass, that it would avert the most serious climate change and begin to restore pre-industrial atmospheric chemistry, returning Earth to the comfortable Holocene conditions in which we evolved.
During interglacial periods, the Earth normally enjoys relatively stable weather patterns and increases in biodiversity and expansion of vegetated ecosystems. That is changing. A temperature anomaly of approximately 1ºC is currently responsible for extreme weather swings [NRC 2010] and amplifying climate feedbacks, which include the melting of glacier and polar ice at accelerated rates [Joughin et al. 2014a and 2014b, Rignot et al. 2014], large plumes of methane rising in Arctic oceans, [Vonk and Gustafsson 2013, Shakhova et al. 2013] and the massive decomposition and outgassing of the world's tundras. [Semiletov et al. 2016] If unchanged, our grandchildren will inherit a planet with greatly reduced biodiversity, accelerating desertification, increasingly severe and frequent heat waves, storms, floods, droughts, rising seas, flooded cities, Arctic vortices, forest fires, and crop failures. [Strauss et al. 2015, Winkelmann, et al. 2015] Ominously, many of these forecasts exclude the potential effects of significant releases from the estimated 10,000 petagrams Carbon (PgC) from methane hydrate deposits in the oceans and permafrost that would augur additional feedbacks, such as the spiking of atmospheric water vapor [Dessler et al. 2008, Fasulo and Trenberth 2012], and raise the likelihood of greenhouse runaway, with catastrophic implications for life on Earth. [Bates 1990, Kennett et al. 2003]
If the burning of all fossil fuels were stopped today, the effect on global climate would be minimal. [IPCC 2007] This is the result of the chemical inertness of the principal greenhouse gas, carbon dioxide (CO2), and the thermal and chemical inertia of the world's massive mineral, oceanic and forest carbon sinks. [Inman 2008] While switching from fossil to renewable energy sources is necessary and desirable for ecological, economic, and health reasons, it is no longer sufficient to stabilize climate. What is required is the direct, rapid, massive, and sustained removal of petagrams of carbon dioxide from the atmosphere using effective, timely, verifiable and economically sustainable methods.
There are compelling reasons for an extremely rapid implementation of such an undertaking. Within a few decades of business-as-usual, extreme climate volatility will make forestry and agriculture very difficult and no longer cost-effective for large regions of the world. [Solomon et al. 2011] Furthermore, at the current atmospheric CO2 concentration of >400 ppm, the planet has passed the threshold into a region in which a methane-emissions-driven runaway climate is more likely, and where even more severe amplifying climate feedbacks are possible. It is urgent to 1) sequester all the current and future global fossil fuel CO2 net emissions and 2) rapidly bring atmospheric CO2 from greater than 400 ppm to well below 350 ppm.
We present here a prescriptive model that simulates planting a vast, global, climate-resilient forest of mixed species and mixed age in non-forested and semi-forested regions of the world. Such regions include remote ranges, abandoned farms and pastures, hillsides, clear-cut or fire-damaged forests, and arid and desertifying regions that overall amount to an area we estimate at 1.5 Gha (gigahectares, or one billion hectares). Table 1 shows the components of that estimate, which are drawn from a study of the global bioenergy capacity. [Smith et al. 2012] We do not include existing productive farms and pastures; however, farming desirable tree species for timber, fruit, nut, protein, oil, fiber, forage, nitrogen, medicine, windbreaks, shade, and ecological services can be encouraged. Additional land area could be obtained from reclamation of the urban or periurban environment and inhospitable zones such as brownfields, deserts and floodplains.
Our model predicts that, by using a method we have termed Climate Ecoforestry (CE) at the rate of 50 million hectares per year (Mha/yr) on the available 1.5 billion hectares (Gha) of land, average carbon sequestration rates of 3 to 5 petagrams Carbon per year (PgC/yr) can be reached. This represents approximately half the current net global emissions [Hansen and Sato 2004] and a reduction in atmospheric CO2 from 400 ppm to 350 ppm becomes possible in the near term with emissions reductions. Our model employs satellite terrestrial NPP (Net Primary Photosynthesis) data to determine priority areas for conversion. [Boden et al. 2015]
In our CE method, atmospheric CO2 is stored as standing forests, labile soil organic matter, and as stable (recalcitrant) carbon in the soil. Carbon sequestration rates up to sixteen times that of conventional plantations are achieved by intensive biomass planting, selective (step) harvesting, and biochar manufacturing [Lehmann and Rondon 2006]. Biochar in turn makes possible the intensive growth of climate-resilient forests in poor soils at improved success rates. [Thomas and Gale 2015] Biochar plays a dual role, storing carbon as stable soil amendment and acting as a single- or multiple-application biofertilizer. [Mulcahy 2015, Preston 2015, Lehmann and Joseph 2009] Both the revitalization of soil fertility and the stable residence of carbon in the soil linger at millennial time-scales. [Schmidt et al. 2011]
Although we accept as an estimate that the amount of underused land initially available for CE is at least 1.5 Gha worldwide [Smith et al. 2012], the CE 24-year cycle can, in principle, be repeated indefinitely on the same land and in newly-restored land as it becomes available. The long-term continuation of CE cycles would, in effect, be equivalent to recapturing the carbon originating from half a billion years' photosynthesized sunlight and converting it into replacement for the soils and forests removed from the surface of Earth over the past several centuries, as well as an active, sustained "sponge" for atmospheric carbon following the phasing out of fossil energy.
Climate Ecoforestry consists of continuous, dense plantings and subsequent timed, selective harvestings of hardy native trees and perennial plants performed in a socially responsible and economically sustainable manner.
Planting proceeds most rapidly where conditions are more productive, only gradually reaching into the less-productive areas as conditions improve enough to insure high sapling survival and seed germination rates. Plantings can advance into arid or wet regions by following water sources and patch planting, encircling and fragmenting less well-suited areas. Permacultural methods such as windbreaks, hugelkultur, chinampas, swales and keyline dams expedite the process. [Bates 2010].
Seedlings are begun in biochar/soil mix amended with beneficial microorganisms and nutrients and, when the saplings are sturdy enough to tolerate field conditions, transplanted together with their soil plugs. At transplanting, additional, biologically augmented biochar is mixed with the soil at root level, covered, watered, and mulched. For the next few years, water and protection from farm animals is necessary and is accomplished by means of fencing, fodder trees, and animal management.
The actual startup of any CE project requires that a modest quantity of biochar to be available for initial plantings. After the first three step-harvests in years 3-5, the project generates its own.
We estimate a crew of 6 nursery workers, planters, tree-carers, charmakers, and support personnel can plant and process 500 trees per day using hand tools. Working 250 days per year during the best seasons and good weather, such a crew can plant and process 50 hectares per year.
We estimate that planting and processing at the rate of 50 Mha/yr, the CE model could profitably employ about 10 million people over the entire 1.5 Gha designated for this purpose. At 50 Mha/yr, 1.5 Gha would require 30 years to establish and would then be in continuous rotation.
The management of Climate Ecoforestry is more cost-effective and less vulnerable to corruption when it is designed as a community project, as outlined in the guidelines of various PES (Payments for Ecosystem Services). [Forest Trends and The Katoomba Group 2008]
Goal maximization, as well as financial returns for planters, managers and landholders, are obtained by selective harvest in regularized steps. The periodicity of the steps is a function of growth rates of the various species. So, for instance, fast growing Bambuseae such as Phyllostachys aureasulcata will double in biomass annually in both temperate and tropical climates within a range of known latitudes and elevations. [Hidalgo 2003] Plantations can take 3 to 5 years to establish before harvest commences, and then harvest is regulated so as to neither harm the grove nor hinder grove expansion, if expansion is desired. A harvest of, for instance, 30 percent of the grove — the oldest culms — would be sustainable if soil fertility is replenished as the method contemplates.
A second example would be a hardwood temperate forest, seeded with diverse species, including those that favor ground cover and understory. Depending on seeding density, the canopy may take 20 years to close, but in the interim, poorly developing, thickly sown, and less desirable varieties can be removed at regular intervals, opening space and increasing nutrient flows for the more desired varieties and diversities. The biomass being removed annually is approximately the same each year following establishment. At full maturity, the forest can either be left alone to continue its somewhat slower sequestration work, or it can be “patch harvested” and reseeded to sustain the juvenile growth rate.
What is contemplated by the CE method, because of the social and ecological dimensions, is not a typical monocropped plantation designed to maximize access for machine cultivation, but rather a cross between a natural field or forest and a horticultural garden. It is a cultivated ecology, an approximation of natural succession. An example of this can be seen in the farm of Roberto Muj in Chimaltenango, Guatemala. [Toensmeier 2016] Elevation is about 2200 meters and most of the year is dry, with a 4-5 month rainy season. The farm is laid out as a perennial alley crop contour strip in which rows of productive trees alternate with perennial herbaceous crops. Trees include citrus, avocado, sweet gum, alder, peach, mulberry, fig, macadamia, and yucca izote. Herbaceous crops in the alleys include aloe, taro, alfalfa, beans, vegetables, kale, cut flowers and medicinal plants. Free-range swine and poultry are provided selective access to the alleys. As trees and woody plants are coppiced and weeded, predictable amounts of biomass are produced. Biomass is also produced from patch rotations involving annuals that require direct sun, such as maize, tomatoes and peppers, cleaning the harvest, and from periodically removing older perennials and replacing them with seedlings. The needs of the farmer for market crops, home food, fuel and fiber are met, and the demands of indigenous biota are served. Because of the ability of such systems to elevate photosynthetic efficiency over mechanized field cropping, and also because of their greater resilience with regard to weather extremes, they are more productive.
Modeling Biomass Growth
Consider the sigmoidal growth curves typical of most living things. There are 40,000 – 53,000 tropical tree species alone. [Slik et al 2015]]. Their actual biomass growth histories are largely unknown and their population densities remain unexplored. In Poaceae, which is a large family of woody perennial grasses with over 10,000 species, there are fast-growing and slow-growing varieties spanning nearly all terrestrial biomes. Among one subfamily, Bambuseae, there are 91 genera. Some individual species are capable of growing 5 cm/hr. Others grow very slowly. There are also dynamics of nutrient availability, microclimate, rainfall, and other factors that affect performance.
Therefore, we proceed by simply adding together three typical sigmoidal growth curves, each of which is a rough phenotype representing the biomass growth history of many tree species. Note that plant species displaying faster growing rates often attain a smaller final biomass than the slower species. Figure 1 illustrates that their aggregate history curve is insensitive to the characteristic details of any single history, and shows how biodiversity reduces the growth latency period of new mixed-species forests.
We define a “forest element” as 16 trees planted in an eight-meter by eight-meter area. In practice, each element will typically be populated with a mix of plants suitable for the local ecology, with each element containing some fast-, medium-, and slow-growing varieties, as shown in Figure 1. Their yearly biomasses can be measured and summed, and their individual and aggregate histories tabulated to yield net carbon storage. Mass units were calibrated using NPP data from NASA’s Terra (MODIS) satellite data, in order to obtain real-life results. [Liang et al. 2006]
Creating a significant reduction in the planet's atmospheric CO2 requires sequestration rates which rise very rapidly to store the global yearly emissions and continue holding that carbon away from the atmosphere for very long spans of time. To accomplish this we assume high-density tree planting, followed by step-harvesting at each of four canopy closures, and conversion of sequestered carbon from lignin to biochar. Frequency of intervention will vary by local conditions and climate. We reserve thirty-six percent of the harvested biomass for the manufacture of biochar. There remains a substantial resource for the production of fruits, nuts, protein, fodder, lumber, the return of labile carbon to the soil, and the sundry needs of a vibrant ecosystem. [Chazdon et al 2016]
Since it takes 2.12 PgC to raise the atmospheric concentration of CO2 by 1 ppm, [Hansen 2009] a reduction from 410 ppm to 350 ppm requires the storage of 127 PgC. By storing current net emissions of ~5 PgC/yr and an additional 10 percent per year of legacy CO2 (12.7 PgC/yr), and barring changed conditions, [Kennett et al 2003] we can recover to atmospheric concentrations of 350 ppm in about seven years. Our CE model simulation shows that this goal of 17.7 PgC/yr can be met and, as we will discuss separately, will eventually become self-financing.
Recent work in the Latin American Neotropics below an altitude of 1000 m. confirms that, even without applying biochar, step harvesting and reseeding, or accounting for accelerated climate variability and other uncertainties, natural regeneration of secondary regrowth forests can sequester 8.48 PgC in just the above-ground biomass covering an area of 2.4 million square kilometers (28.1 percent of the total region studied) over 40 years. [Chazdon et al. 2016] This unassisted natural regrowth corresponds to net CO2 sequestration of 31.09 PgCO2, or the equivalent of all fossil fuel use and all industrial processes in all of Latin America and the Caribbean from 1993 to 2014. The addition of processes such as biochar, step harvesting and reseeding, with a fabric of social permaculture to increase productivity, biodiversity and establishment rates, would augment these results.
The success of our model in reaching these goals depends heavily on the application of biochar. Biochar is "a solid material obtained from thermochemical conversion of biomass in an oxygen-limited environment." [Lehmann and Joseph 2015] In addition, to be recognized as biochar and certified by one of the various soil amendment safety authorities, the material has to pass a number of material property definitions that relate both to its value (e.g., ratios that relate to the degree of charring and therefore mineralization in soil) and its safety (e.g., heavy metal content).
The principal benefit of biochar derives from its ability to fertilize unproductive soils while remaining in a stable form for long periods. [Lehmann et al. 2006] Biochar applications produce the greatest improvements on the worst land. [Lehmann and Rondon 2006] Figure 2 shows an average 50 percent increase in agricultural productivity at cumulative application rates of <15 tC/ha (metric tons Carbon per hectare).
Biochar produces a 50 percent improvement in productivity of tree biomass at these rates. [Thomas and Gale 2015] Our CE model assumes a change of Net Photosynthetic Productivity of 41 percent as a world-average gain in tree biomass resulting from a single 5 tC/ha biochar application when transplanting saplings.
After harvesting for food, fiber, leaf protein and perhaps small-scale ethanol or biodiesel over the productive life of the tree, woody wastes from production and phased specimen removal may be transformed to biochar by pyrolysis. Either the heat or captured syngas from that process can be used to produce electricity. In the case of direct heat transfer, the generator may be powered by a low-cost simple heat engine such as Stirling, Rankin or Minto cycle. In the case of captured gas, the generator may be powered by internal combustion engines or gas turbines.
Distillation produces another byproduct in dried distillers grain (DDG). Because fats and fiber are removed in the early steps of the process, protein is concentrated in distillers grain and the appropriate distillation methods can provide 15 percent better protein availability than the original grain. [Kelzer et al. 2011] There is therefore no dichotomy between food and fuel. An ethical bioeconomy produces more of both. Unused, stale or spoiled DDG is also a potent fertilizer and another potential feedstock for biochar. [Hofman and Baker 2010]
When biochar is added to DDG for animal feed, it becomes an important nutriceutical, improving digestion and protein absorption, and a pharmaceutical, reducing the need for antibiotics. [Schmidt 2012] After passing through the intestines of the animal it is deposited in the floor of the barn, field shelter or field, where it absorbs urine and nutrients from feces, becoming enriched in nitrogen and potassium, among other micronutrients, for later slow discharge. From there it is composted, either by the farmer or by nature, and redistributed to fertilize the soil.
Biochar straight from the pyrolysis kiln is hydrophobic and sterile. [Lehmann and Joseph 2015] If amended to the soil while in that condition, it scavenges nutrients and microbiota from the existing soil profile, depleting the availability of the nutrients to the roots of the plants and possibly propagating parasitic and growth-inhibiting microbial communities. For this reason biochar must first be conditioned, or “charged” to render it hydrophilic and teeming with beneficial microorganisms. [Bates 2010] Biochar that is “hot quenched” with urine produces 30 percent greater vegetative growth than biochar that has been “cold quenched” in water. [Schmidt et al. 2015]
Healthy soils contain 50,000 species of bacteria and 50,000 protozoa per gram. Those protozoa eat 500 million bacteria per day, which releases 400 million molecules of nitrogen, or 7 nanograms per cubic centimeter (ng/cm3) of root surface. Plants only require 0.2 ng/cm3. Much of the remainder is attached to fungal hyphae as oxylates for further distribution. [Ingham et al. 1985] Plants are fed by bacterial exudates moderated by fungi, non-parasitic nematodes and other members of the soil microbial community. [Stuart, et al. 2016] It is possible to stimulate, nourish and revitalize this soil community, virtually anywhere, by making aerobic, thermophilic compost and/or compost tea and then inoculating biochar with beneficial microorganisms for transfer to soil.
When biochar charged with compost tea is applied as a soil amendment, its porous structure and available nutrient store permit bacterial nodules in the soil to continue the favorable aerobic conditions necessary for continuous growth. [Lehmann and Joseph 2015] These beneficial bacteria consume any weaker non-beneficial microorganisms. [Lowenfels and Lewis 2010]
The Self-Finance Mechanism
Agroforestry provides many useful products and services to modern economies but is often outcompeted in the marketplace by other methods of production. It can financially succeed or fail based on site selection, local markets, and other factors that raise or lower risks. [Haugh 2006] To reach the global scale of response required by the pace of climate change may require added entrepreneurial incentives. Biochar provides these.
Biochar can be used for a range of applications: carbon fertilizer; compensatory fertilizer for trace elements; compost accelerator; substitute for peat or vermiculite in potting soil; silage moderator; feed additive/digestive supplement; probiotic/nutriceutical; litter additive; slurry treatment; manure composting; water treatment in fish farming; insulation; air decontamination; decontamination of earth; humidity regulation; dust and pollen scrubber; electromagnetic radiation screen; a barrier preventing pesticides getting into surface water; oil spill remediation; biogas slurry treatment; active carbon filter for smoke and exhaust; pre-rinse additive; media for composting toilets; carbon fiber; electronic semiconductors; batteries; metal reduction; alloys; cosmetics; soaps; skin-cream; therapeutic bath additives; paints and stains; food colorants; energy pellets; poisoning control; detoxification; carrier for active biopharmaceuticals; functional deodorant underwear, socks, shoes and fabrics; thermal insulation for clothing; infrared screens for snipers; filling for mattresses and pillows; and an avenue for greenhouse gas mitigation. [Schmidt 2014]
In each of these transformations of forest products reside opportunities for microenterprise. Merely managing a forest for carbon sequestration would not provide adequate returns to attract investment of capital or labor. By cascading forest products, Climate Ecoforestry can finance itself without imposition of regulatory incentives and disincentives or by the (temporary) diversion of funds from other sources, such as the Green Climate Fund or the Global Environmental Facility.
During the process of making biochar, a large amount of heat is emitted which is available for domestic, commercial, and industrial uses. Volatile gases (syngas) produced in the process of pyrolysis may be stored for energy production along with other valuable industrial chemical feedstocks. Agricultural and forestry wastes such as forest residues, mill residues, field crop residues, or urban wastes provide a conservatively estimated 0.16 PgC/yr of available feedstock. [Lehmann et al. 2006] Biofuel production using modern biomass can produce a biochar byproduct through pyrolysis that results in 30.6 kg C sequestration for each GJ of energy produced. Using published projections of the use of renewable, carbon neutral fuels in the year 2100, biochar sequestration could amount to 5.5–9.5 PgC/yr if this demand for energy were met through pyrolysis, which would exceed current emissions from fossil fuels (5.4 PgC/yr). [Lehmann et al. 2006] Biochar soil management systems can deliver tradable C emissions reductions and sequestration that are easily accountable and verifiable.
Biochar-making technologies range from simple, inexpensive barrel retorts and cone-shaped portable or in-ground kilns, household and institutional multi-purpose biochar stoves, to industrial-scale pyrolyzers or biorefineries that co-generate electricity, leaf protein, biofuels, and biochar. [Fuchs, et al. 2014] In reforested areas this opens the potential for enterprises supplying home stoves and heaters, fuel pellets, and village-scale pelletizers. [Mulcahy 2015] Biochar manufacture achieves a carbon efficiency of 1:2.2 in low-tech smokeless woodstoves that are fitted with simple gas-cycling retorts. At larger scale these efficiencies might be improved, but for the purpose of our model we assume carbon retention of 1:2.2 (45.45 percent) in biochar manufacture and 1:1 for above and below-ground live biomass.
Global NPP, Ecological and Social Constraints
Ecoforestry takes a holistic approach that can be likened to a three-legged stool. The three legs are social or cultural; ecological; and economic. Agricultural practices must place equal value on all three of these structures to attain stability. If any of the three is weak, the entirety is placed in jeopardy.
Climate Ecoforestry is constrained by the culture, ecology and economics of each region. Some trees require more water or particular soil types or would outcompete native plants that may be important for other cultural, ecological or economic services. Planting densities and rates must depend on preliminary holistic analysis that weighs human family and community needs in the balance with ecological need. This balancing must determine that the estimated three-prong benefits are greater than the negative effects and not merely rely on expected economic returns. A harmony must be struck between a respect for the local culture, ecology, biodiversity, microclimate, and soil quality and a gradual “push” to improve productivity. Here partnerships with local landowners and the adaptation of the sophisticated techniques of traditional and contemporary indigenous agroecologies are valuable tools.
Along with normalizing the global climate, Climate Ecoforestry also raises the productivity of the world's soils. This can be verified by using carbon content as a proxy indicator for soil fertility. Our model indicates CE would make available an average of 5 tC/ha per cycle for CE-afforested land, and 15 tC/ha to agricultural land, most particularly in “under-used” degraded lands where people and ecologies suffer the most from adverse climate events. Since only modest amounts of biochar are required for soil improvement, the surplus can be applied to the recovery of abandoned farmland and arid lands. If 50 percent of the biochar is reserved for forestry and 50 percent for agriculture, the biochar from one hectare's step-harvests can fertilize approximately 5.5 hectares of new tree saplings applied at the rate of 5 tC/ha, and 1.85 hectares of agricultural lands at an average rate of 15 tC/ha. [Lehmann and Rondon 2007]. In order to assure retention, biochar is applied at the nursery stage in potting soil, and later during field transplanting, at the base of the root ball to achieve an application rate of 2 kgC/sapling. The CE model assumes that 90 percent of amended biochar is retained after an initial 10-year period during which the labile component leaches away or is taken up by plants, leaving only the stable, recalcitrant form of carbon.
The CE process could be applied in wetland environments or at the margins of deserts, in the region where NPP declines due to poor soil formation or adverse conditions. The advance into wet or arid lands must be gradual and slow, at rates limited by improvements in the microclimate to avoid wasting seedlings and labor, disturbing local hydrological cycles, or causing too much disturbance in the existing ecology. This is one of the distinctions between agroforestry and ecoforestry.
Climate Ecoforestry can include a variety of species that are native to similarly developing ecologies, culturally adaptive, and economically beneficial. Moreover, selected species should demonstrate the ability to prosper under increasingly adverse climate variability. Some examples of multipurpose hardy trees include huarango, moringa, and leucaena. Multipurpose biomass grasses include bamboo, hemp, miscanthus, and vetiver that are ecologically resilient and both culturally and economically advantageous. Shade-tolerant tree and plant varieties can be undercropped below sun-loving canopy varieties, and climate-hardy cultivars may be grafted onto proven natives, a practice known as assisted gene transplant. [Aitken and Whitlock 2013]
The traditional swidden agroforestry methods employed, for instance, by the Classic Era Maya, while highly-productive and ecologically beneficial, were extremely labor intensive and adapted to the biomes found in Central America. [Ford and Nigh 2015] However, a simplified Mayan agroforestry method has been published [Teul et al. 2014] that in addition to agricultural crop yields, produces a biomass creation rate 2.4 times greater than our CE model, and a correspondingly high production of biochar. Agroforestry methods like this employ a limited number of species that are beneficial to the soil and cropping operations, and are applicable to populated regions where farming is done. Our CE method includes agroforestry, but also planting a larger number of regenerative species to stimulate a vibrant natural ecology in areas not employed in food and forest product production. CE assumes a balance of cultivated and wild lands.
The model is unable to predict uncertainties that may propagate through anticipated but largely unknown impacts of climate change, global resource depletion and human population expansion, especially in vulnerable regions.
Climate Ecoforestry's benefits could be nullified if the world's population continues to grow at present rates. More people require more food and more land, adding to the planet's CO2 burden.
So is CE ultimately futile? If raising the living standards can most quickly stabilize population growth, the CE model provides one approach to the elevation of living standards. This model drives itself economically and therefore can continue as long as there are people seeking a livelihood.
Unlike other carbon capture methods involving air scrubbing, geoengineering, and afforestation that require external monetary inputs and incentives, the method we describe here is not only self-financing but profitable, allowing the internal flows to be directed outwards towards other uses.
Many of these outputs are described elsewhere. [Schmidt 2012] We have described a single cascade: biomass-ecological services-food-feed-fuel-biochar-energy-nutriceutical-biofertilizer-carbon sequestration.
The relatively small amount of 1.5 Gha of potentially available land is not a limitation. The 24-year CE cycle can in principle be repeated indefinitely by beginning again on the same land, harvesting the oldest trees, and densely replanting the same forest cells in the now biochar-fertilized soil. In addition, relatively marginal land will have been restored, allowing the expansion of CE into previously unsuitable territories.
The United Nations Food and Agriculture Organization (FAO) defines "climate-smart agriculture" as "agriculture that sustainably increases productivity, resilience (adaptation), reduces/removes greenhouse gases (mitigation), and enhances the achievement of national food security and development goals." Our prescriptive model shows that if Climate Ecoforestry were implemented at the rate of 50 Mha/yr over an area of 1.5 Gha, it could store current anthropogenic emissions and meet the goal of sequestering additional annual petagrams, while supplying many other benefits.
Stabilizing the climate and regreening the planet can redirect the role of humans as the top polluters and predators to instead become protectors, partners, and stewards of life on the planet. By addressing the social inertia component to climate action, Climate Ecoforestry represents a green technology that might enable us to go beyond mere survival and reestablish a garden planet.
— Albert Bates and Frank Michael, Global Village Institute for Appropriate Technology, September 2016