20 years of carbon sequestration on 10 tropical acres

Agro-Ecology Journal:
20 years of Carbon Sequestration on a 10-acre tropical farm.
By Stephen (Esteban) Bartlett

Subtitle: Only Small-Scale Community-Based Agriculture can Cool the Planet and Care for the Earth’s Fertility

El Guao, Dominican Republic
December, 2009

It was in 1990 that I first saw (and decided to buy) the 10 acres of land that was to become the source of life and livelihood for my then young family and for the families who would work with us and for us. In rolling hills of dark red sandy loam mixed with caliche rock, overlooking the Atlantic ocean about 2 miles distant and 650 feet above sea level, an ageing widower lived and worked on this land (now for sale) amidst a community of struggling families and individuals. There was no retirement for this gentleman as long as his children did not send him the support he needed, so he decided to sell the farm and move to a small house in town. He was getting tired and his body was getting too old for the physical rigors of subsistence farming and forestry. He had a daughter in town who wanted to support him there.

Absentee landholders then owned and in 2010 own even more today of the pastured fields of these coastal hills. These urban owners live in nearby towns or cities or in the capital city of Santo Domingo four hours drive to the south. For at least three generations, the land supported a fairly dense settlement of family farms, whose abandoned homesteads were in 1990 only in evidence by clusters of fruit trees and perennial herbs and flowers surrounded now by open stretches of pasture grasses and scattered royal palms, bordered by the living fences strung with barbed wire known as ‘piñon´(gliricidia sepium). The grandchildren or great-grandchildren of the original settlers on this once dense tropical forest were to be our neighbors, who today have been largely replaced by Haitian immigrant agricultural workers, a phenomenon with its own roots in international capitalism and neo-colonial economic policy. The dozens of Haitian young men living in El Guao in 2010 occupy the old houses built by Dominican family farmers who have moved to the cities or died off.

In looking at the transformations that have taken place in the community of El Guao from 1990 to the eve of 2010, I am convinced anew, and with greater clarity, of this essential truth as expressed by the Via Campesina movement: without small-scale community-based farming there will be no solution to the fatal downfall of humanity due to natural calamity related to global warming and climate shock. The reason for this is simple: short of eliminating all humans from the face of the Earth, or returning human presence to small bands of hunters and gatherers, only small-scale farmer-foresters in communities rooted to the land are capable of practicing the agro-ecological farming methods that are proven to allow the Earth to store the excess CO2 released into the atmosphere by deforestation and fossil fuel burning, a long-term calamity that is currently threatening our species´ collective future. And there is a corollary to that conviction: only small-scale community-based farming can provide for a wide and equitable distribution of the wealth derived from the productive capacities of the land under human labor. Hence, social justice and the sustainability of flourishing communities also depend on the restoration of small-scale farming. The restoration of family farm economies is an essential win-win solution for all but the shareholders and executives in the world’s largest corporate monopolies.

In 1990 this 10 acres that was to become our family farm was owned by Isidro Santo and, by inheritance law, the children of he and his deceased wife Candida Alvarez, who had to sign off on the sale. The land was mildly forested with a shaded coffee grove (about an acre), a crop field (conuco) and many fruit trees around the palm board house and also scattered among the mostly sloping pastured fields, surviving from previous garden plots turned to pasture now. About half of the farm consists of a rocky expanding slope bordering the road to the north (facing the ocean horizon) and a back southern half of fairly flat wedge where one of the crop fields and coffee grove are located. A natural waterhole that has never dried up in living memory, bordered by a huge piñon and a giant mango tree, collect the rainfall runoff from much of the pastured hills. Isidro the ageing farmer was primarily a bee keeper and a wood sawyer, a member of those breed of men who use 7 foot long two-person saws to cut planks and beams for the construction of houses and outbuildings. Isidro had planted many orange trees over the years which were now in their late years of productive life and his small and mature coffee grove likewise produced a couple hundred or so pounds of coffee each year. There were also a wide variety of edible fruit trees, ranging from tropical plums to jobo de la India, nispero, tamarindo, and several others. The farm is surrounded by a 500-acre cattle finishing ranch owned by one of the largest landholders of the area, who also own a slaughterhouse in the capital, from which beef is exported to the U.S.

A typical pattern of tropical land use that allows for the maintenance of soil fertility over time is shifting cultivation. When virgin or mature forest stands are first cut down, the cycle begins. On the land where the forest has been cut, and often burned as a means of removing the considerable mass of fallen wood, crops like corn, beans, squashes, peppers, followed by cassava, cocoyams, bananas, plantains, etc… are planted in the new layer of ash and the ¨rested¨ soil that has lain under forest for many years. After the first year or two of corn and bean crops, the farmer will also plant a scattering of avocado, lime, mango, breadfruit, orange, coconut tree seedlings and allow for the growth of a few volunteer royal palms (for the oil seed to be fed to pigs and the thatch for the roofs of the dwellings). Some farmers with an eye for diversity and wood products, like Isidro, will also protect valued timber tree species here and there, for use over time in maintaining or building structures on their land. In our area species such a cigua, cabirma, cuerno de buey, roble, Juan Primero, mahogany were planted or allowed to grow after sprouting naturally through bird droppings most often. Once the land has begun to lose its fertility for crops like corn and sweet potatoes, it may be used to cultivate leguminous crops like peanuts, which was a widespread crop in these light soils supported by the peanut processing plant in Abreu (about 4 miles down on the coastal highway). After a number of seasons of peanuts or two or three seasons of corn and beans, the exposed soils are typically in need of a rest, so the farmer switches over to cassava, or pigeon peas. By then some of the fruit trees are starting to flower and bear fruit, and some of the palms have begun to grow into trees and shoot skyward. In the sandy loam the heavy rainfalls of this once rain forest leach many of the nutrients in tilled and cleared soils down into deeper subsoil layers, unavailable by the annual crops but reachable by the roots of fruit trees. If a farmer decided to plant coffee or cocoa trees in a former ´conuco´(the name of the area where food crops are grown), they would traditionally also plant tree species known to favor coffee with their shade and physiological complementarity, like amapola, guama, and also breadfruits or castaño.

My approach to the problem of exhausted soils was a system of agro-forestry within the fields. I planted leucaena trees grown in nurseries with the symbiotic root fungi in long north-south rows. The forage of these trees, once established, would provide a steady diet of green manure (from the 21% protein leaf) to the soil and/or food for cattle who would in turn manure the soil. After the establishment of those trees and the re-introduction of cattle into those fields, our cows had the unusual distinction of producing more milk during times of drought, when we were primarily feeding leucaena leaf forage to make up for the loss of pasture grasses.

As I have just alluded, another shifting rotation scheme short circuits the longer cycle through coffee and cocoa and involves growing corn on plowed or herbicided ground and then planting grass for pasture. In the case of Isidro and many of the local farmers of the area, local milk and cheese production has encouraged people to raise milk cows because of the ready market for dairy products. So old crop and orchard areas are sometimes planted in grass too, which accounts for the many fruit trees dotting our pastures, a development that has, as a side effect, demonstrated that cows love fruits, from avocados to mangos to grapefruits to jaguas to sour oranges. Cows love a diverse field as much as anyone, for shade and sweet snacks! The milk fat (cream) that rises to the top of the pot when pasteurizing milk from our cows has an orange and dark yellow hue, due to the high levels of beta carotene in the cow’s diets. Absolutely delicious and highly nourishing, particularly when processed into yogurt or soft farmer’s cheese!

Once these fruit and forest trees grow tall enough and the cocoa or coffee crops come in, the farmer needs to keep pruning the shade trees back so that the shade does not become so deep that the coffee or cocoa no longer produce. Ultimately, as the coffee or cocoa trees grow old, the farmer allows the canopy to close in with the shade trees and any other tree species that now fill in any gaps. Woody vines also grow up in such canopies. We had a huge old amapola tree with a thick woody vine growing up into it, allowing a person to climb up and up the tree trunk like a ninja and rest high in the canopy on a tree branch overlooking the coffee grove. Snakes, iguanas and many insects and wild plant species, including many considered to be medicinal, would come to inhabit such old groves or the borders of those groves. On the edges of such groves food crops like tall bananas, cocoyams (the tropical taros that tolerate shade), African yams and a native root crop similar to yams called mapuey (whose vines climb up into the canopies) can continue to be cultivated.

The pastures are typically bordered by living fence trees. The gliricidia sepium tree is incredibly beneficial to farmers and ranchers. Branches of this tree can be pruned off the tree and with a point cut in their lower end, jammed into the ground. With barbed wire then stapled to them, the tree will take root and become part of a living fence line. As long as the pruned limb is tall enough so that cows cannot graze the highest leaves, these trees will typically survive the pruning and vegetative planting and set roots. The leaves are a valuable forage crop for cattle and the flowers of the piñon bring on the biggest honey flows for beekeepers. Those wanting to make some extra cash, can use piñon prunings to make a high quality charcoal. The leaves of piñon are also medicinal, serving to calm skin irritations by mixing in a bath. The older, thicker specimens with their extremely hard heartwood are carved with an axe and used as corner posts when buried in the caliche-rich soils with the aid of a coa, a Taino name for a hardened digging lance, typically a steel-headed one in modern times.

The combination of living fence lines and forested groves either for coffee or cocoa, with pastures dotted by scattered fruit trees and palms was the typical agro-forestry scenario of the generations of farmers leading up to our purchase of Isidro´s 10 acres of land. What we then did, and did not do, on the land led to a further increase in forest cover and overall biomass over the 20 years of living and working on this land, the last 13 years as absentee owners ourselves, coming for periods of time to live and work but mostly administering the land use of a Dominican farm overseer and his young family. The overseer of our farm had a low impact style of land management and was oriented toward the forest species mentioned here, and he was highly motivated to cultivate a variety of forest-friendly food crops.

During the six years we lived on the land from 1990 to 1996, we adapted to the local economic realities. We bought 3 heifers from good stock and milked them daily once they became full-fledged cows after giving birth. This provided us with a steady stream of income. To increase that income, we processed a portion of the milk into yogurt which we sold by the gallon on our twice weekly trips to town in our pickup truck (a vehicle that we had shipped from the US but that 10 acres could not economically support in the long run unless it was used for other income generating activities). About 4/5 of the land was in pasture, the rest in conuco/orchard and coffee grove. To maintain the pasture that brought in cash from milk cows or beef cattle required a difficult choice: one either had to hand weed the pastures on a regular basis, hiring temporary workers to assist us, or use herbicides to control the weeds. Weeds and an occasional drought would also cause a lot of the pasture grasses to die, which would then have to be replanted on cleared ground. At the time, this was done by cutting the African pangola grasses from thick stands or from neighbors plots, or where grass was being removed to plant a conuco, and transplanting the grasses into our land with pickaxes after a heavy mowing and weeding operation. Plowing could also be used to try to remove and kill weeds, but much of our pasture was too hilly and rocky for plowing. Without exception, all of our neighbors had come to rely on using herbicides like Round Up (Gliphosate) or Gramozon and other woody plant herbicides to provide space for the grasses to flourish. Vines like bejuco caro were constant headaches, since even herbicides could not kill them, and they had to be dried, piled and burned. In our area most of the pastures were heavily stocked and most were overgrazed, despite the high rainfall-high growth conditions. The more successful ranchers who were buying up the lands of the less successful (or less capitalized or less able financial managers) would sell off cattle at strategic moments to allow the grasses to rebound from heavy use, thus avoiding weed infestations or heavy erosion over time. On lands constantly grazed, as with milk cows that cannot be sold off periodically, the reversion of pastures to less productive grass species like saladillo or gramma was commonly observed. In fact, I believe that it was the advent of herbicide use in pasture establishment and maintenance that allowed for large land owners to expand their holdings economically. They could pay for a backpack spray pump, and the chemicals and train a worker or two to do the spraying, with a donkey to carry the water. Otherwise hired labor costs would have made such expansions far more expensive, and less competitive with households that were providing much of that labor from within the family (ie unpaid). In a few seasons of timely and focused herbicide use, most of the weed species become greatly decimated, allowing for easier pasture maintenance. From our own experience, trying to maintain pastures manually was a never ending, toilsome and expensive activity accomplished by hiring several workers armed with machetes, pickaxes, and scrupulous enough to make fires to kill off the difficult-to-kill vines or thorny invasive species. For more than 15 years we tried to maintain our pastures non-chemically, and since we were not present for 9 of those years and since our farm overseer was getting old and less able to do months of backbreaking, 8-hour days, we had to make a change. In recent years we have made judicious use of herbicides and newly available grass varieties that we could plant by broadcasting purchased seeds, to re-establish pastures overgrazed by 15 years of the lives of our three productive cows and their offspring. During that period our oldest and best Cebu-Swiss cow, Chocolate by name, gave birth to an astonishing 16 healthy calves in her productive life! (The modern industrial milk cow on average does not even reach past her second birth and many do not reach completion of a second pregnancy.)

In addition to shifting cultivation and periodic reforestation of land, pasture grazing patterns are critical in maintaining the fertility of soils (and their ability to store or sequester carbon). Tall stands of grass with well developed root systems hold large amounts of carbon and prevent leaching and erosion of the carbon in soils, as well as the valuable soils themselves. Well-maintained herds who do not overgraze likewise deposit over time carbon in the form of manure, thus bringing more nutrients and organic material (grass mulch and humis) to the surface layers of the soil and to the roots of the grasses. In the same way, shifting cultivation of the kind I described above allow for the land to be put to a variety of productive uses while maintaining an overall density of carbon in the vegetation growing. On a given piece of land in shifting cultivation only in the first year or two is the field fully cleared of vegetation, for the first planting of corn, beans, squashes, peanuts, etc… After two or three years, shifting to cassava, cocoyam, banana cultivation, plowing or uprooting all the vegetation is no longer necessary and would only accelerate the loss of fertility, and the volume of vegetation increases in the 3-dimensional, multi-layer intercropping. The weeds are cut by mowing machetes in what is called ´chapeo´or ´pic a tierra´ work. This does not disturb or turn the bare soil. Root stocks of the bananas and root crops are planted directly into the mowed ground. One or two weeding passes follow to remove or weaken encroaching weeds and vines. The fruit tree seedlings, meanwhile, once mature provide avocados, mangos, breadfruits, coconuts, for many years to come, and continue to increase their biomass over time. They also signify food security for farm families even in times of drought that wither annual crops or heavily-grazed pasture grasses.

I estimate that the overall forest cover of our farm has increased by 30 to 40% due to tree seedling planting and stewardship of volunteer tree seedlings dispersed naturally (ie by birds, bats, etc…), with an increase in vegetative dry weight of approximately 1,500 tons minimum. In addition to the shifting cultivation pattern we have followed, we have planting hundreds of timber, leaf forage and firewood tree seedlings, on plots formerly part of the shifting cultivation cycle, or in open pasture. In particular we have planted about 1,000 acacia mangium trees and perhaps 300 leucaena trees. Hundreds of other trees we protected from vines after their volunteer appearance as tiny seedlings. Despite the unfortunate fact that perhaps 60% of all the timber trees have been damaged by passing wind storms and hurricanes, nevertheless their biomass is still stored in their living mass, or in the humis they are contributing to the soil as they decompose on the shaded forest floor.

Given our restoration of thick pastures to the land, I estimate our pasture biomass has increased by at least 80 to 100%, despite having less total area devoted to pasture (some previously in pasture is now in timber, forage or firewood tree species in whose shade grass cannot grow). I estimate that the total biomass of the farm has possibly doubled or even tripled, when all the timber, firewood, and increased pasture grass biomass is accounted for. The actual dry weight of that biomass increase must be in the order of at least 1,200 to 1,500 metric tons.(One metric ton is 1,000 kilograms, or 2,250 pounds), and it is possibly significantly larger than this. This calculation is based on the following: one mature timber tree yields usable lumber and sawdust and unusable wood weighing more than a metric ton total, not including the weight of the roots. A 40% increase in forest cover consists of, say, some 800 timber trees averaging ¾ of a ton each grown over a total of 10 to 20 years, that would yield 600 tons, plus at least another 150-200 tons in root mass. Increased pasture biomass, including leaf and roots could weigh 6 to 8 tons every 3 months on, say, the 7.5 acres (about 3 hectares of pasture or 24 to 32 tons per year as it is grazed). Over 20 years the amount of biomass consumed by cattle could reach 100 to 130 metric tons, with most of that returning to the soil as manure or trampled grass. The biomass in wood and leaf forage of, say, 3,000 piñon and leucaena trees that line our pastures and grow in north south rows within some pastures must weigh somewhere in the range of 300 tons. A total of 1,500 tons increase to a biomass that must have amounted to at least 2,000 metric tons to begin with in 1990 thanks to the tree planting propensity of the former farmer/forester Isidro Santo. Interestingly, some of the palm boards and two by fours of lumber hewn by Isidro still grace the structure one of the houses on the farm. They are highly durable which conserves their CO2 sequestration for many years.

Please keep in mind that this is entirely a rough extrapolation based on the weight of a single tree after 10, 15 or 20 years, the numbers of trees planted and growing and the estimated weight of a mass of grass mowed from a field based on some literature on the subject.

But the point is this, only through a highly diversified use of the land could such increases in total biomass by achieved, compared to a starting point of an already diverse and significantly forested land use. Small-scale farmers without the support of government extension, infrastructure and marketing cannot afford to plant large areas of their land in forest trees (as we did) whose benefits will only accrue after 10 to 15 years of growth. But given the opportunity to rationally manage land in terms of shifting cultivation, including timber trees, farmers would stand to benefit economically to a large degree, reaping considerable benefits from the sale of valuable lumber, not to mention increased income from charcoal making using the waste wood of a small-scale lumbering operation. Forest management extension programs and support by governments around the world should be a key component for improving farm production, soil fertility and carbon sequestration, as with support for the production of important staple foods for their populations combating hunger both rural and urban. As we know, the larger the land holding, the more likely the production of that land will be destined for exportation, and the profits therefore accruing to the exporter-importers, food processors, and distributors of that food, money that flows away from the farm, rural community and country of production.

A farm and economic policy that would stimulate the circulating of that wealth at the local, regional and national levels, would be a motor for economic development, and a sure vehicle for redistributing wealth and for returning and retaining workers on the land, as independent, autonomous farmers or as decently paid field workers. Agrarian reform is a vital need around the world, if we are to reverse global warming caused by deforestation and loss of CO2 from the land. Agrarian reform that makes land accessible to as many farmers as possible is essential. Such agrarian reform could provide rural communities the kind of support that would allow and encourage them to practice diversified agro-ecological farming and forestry.

The 20 years of tree planting on our farm in El Guao is now yielding excellent lumber for the making of furniture and the building of homes, cut by the low-carbon one man saw techniques. The land now yields large amounts of wood prunings or wood fall that can be (and is) used directly for cooking or processed in rustic but efficient charcoal pyramids into saleable charcoal for cooking food, a renewable form of energy whose CO2 is returned to the forest over time as new trees are grown for future meals to be cooked over. It yields increased soil fertility (and therefore carbon storage) in the pastures heavy with waist high grass, and in the fertility that accrues with shifting cultivation as soil is restored by the gradual restoration of vegetative and forest cover over time, producing edible and useful products throughout the cycle. It yields increased food supply on the farm and in the communities, more resilient to drought or flooding due to increased root mass and depth.

Our former coffee grove still has some coffee plants, sprouted from fallen seed from the mature old trees. But what that grove now yields after hurricanes knocked down the older shade and volunteer timber trees (long ago turned into soil humus or charcoal) is a crop of African yams, cocoyams (tropical taro root) and plantains that is feeding several families in the community. Our farm overseer Vitelbo understands shifting cultivation and he understands the nutrient cycles of land necessary for the food crops that can be grown on land. Yams love the edge of the forest and grow well interplanted together with cocoyams and bananas, as well as wild plants some of which are used as medicines. Yams take a year to yield, but the yield of each plant is a highly nutritious root that can weigh 20 to 50 pounds or more, and once dug up, the semi-perennial vine will continue to grow a new root to be eaten in a year to come. Yam tubors consist of a creamy and dense potato-like root with good protein content, whose taste is beloved throughout the African diaspora, considered the King of Tubors in West Africa. The African Yam, to my mind, is the quintessential crop for tropical humanity: it nourishes like little else can, and it grows in the forest, or at the edge of the forest. Together with bananas and plantains, cocoyams and breadfruits, coconuts and ¨green cheese¨ /avocados, these are the staffs of life for the small-scale tropical farm community, their true wealth and security in a time where forests are being razed across the world. Yams, plantains, coconuts, avocados, breadfruits in local markets are typically signs that the forest continues to grow, as yams need the forest to climb upon. Plantains produce their delicious abundance in small clearings in the forest. Avocados, coconuts and breadfruits ARE part of the forest. African yams for breakfast with free range chicken eggs or for supper with fish or guinea fowl, is the earthy nectar of the Gods, glorious meals of the present and the future for tropical farmers. These forest clearing dwellers are bulwarks against hunger and deprivation. This kind of diversified farming with shifting cultivation represents a low-carbon solution to global warming, with humans still in the picture.

Remember: around the world family farmers are, with the slightest cushion from want, the world´s foresters who cool the planet even as they feed and house themselves and their communities and nations so well! Let´s support them and keep them healthy and on the land through agrarian reform! Help them share their best practices with each other. Help them grow old on their land with their children motivated to continue those practices and lifestyle-culture and to market their excellent food locally. Push for Agrarian reform! Away with corporate food agribusiness and commodity dumping! In with good healthy food and employment for all, with autonomy and dignity! It is not just a ¨good idea¨; it is humanity’s tried and true pathway to survival and well-being.