We tend to divide forests into floors and canopies, paying little attention to what lies in between. Yet forests have multiple layers[i], from grasses and shrubs to trees that have not yet—or never will—reach the heights of the canopy (known as understories). While each plant in any given layer has its own role to play in the health of our planet, it’s the symbiotic relationship of the whole multistrata ecosystem that has the greatest potential to sequester carbon emissions, improve the livelihoods of small farmers, and chart new frontiers in sustainable agriculture.
This process has many names, including layered agroforestry[ii] and MTC (Multi-strata Tree + Crop) systems[iii]. Drawdown[iv] calls it multistrata agroforestry[v], and it’s listed as #28 on their top 100 solutions to reverse climate change. If we can increase the 250 million existing acres of multistrata agroforestry by just 50 million more acres over the next three decades, 9.3 gigatons[vi] of CO2 can be sequestered. Investing just $27 billion toward this goal, moreover, could result in as much as $710 billion[vii] in net profit for farmers—especially those in the most impoverished and climate-vulnerable areas of the world.
How It Works: Benefits and Challenges
Multistrata agroforestry works because of a principle known as the niche complementarity hypothesis[viii]. Put simply, the more species a system has, the more ways it has of obtaining and utilizing resources. These systems are therefore more efficient and resilient—and thus more sustainable—than monospecies systems.
In multistrata agroforestry, therefore, trees’ leaves shade the lower plants from sun damage and dehydration[ix], while their root systems keep the soil strong. Decomposing shrubs and crops enrich the soil with organic matter and prevent runoff. If you take a walk in the woods, you can feel these very effects for yourself. Canopies shield us from rain, wind, and sun, while the leaves and grasses we crunch under our feet nourish the soil. The result is a fertile ecosystem that grows more resilient and healthier crops, both annuals and perennials.
While multistrata agroforestry can come in many forms, two of the most common are shaded perennial systems and homegardens. The former systems tend to have fewer, and more woody, species, as in organic and fair-trade coffee and cacao harvests grown under the shade of banana trees in Central and South America.
Homegardens are the most biodiverse[x] of all manmade land systems, leading Professor PK Nair of the University of Florida, the world’s agroforestry expert, to call them “the epitome of sustainability.”[xi] Professor Roger Leakey found that homegardens in Indonesia, for instance, contain up to 70%[xii] of the number of animal species found in nearby rainforests—themselves the most diverse ecosystems on earth. Similarly, Mesoamerican homegardens average an astonishing 149 species per acre[xiii].
As beneficial as these multistrata agroforestry systems are, their adoption has been slow due to a number of challenges. Agroforested lands are more labor intensive[xiv] to cultivate, since machines cannot easily cut swathes through uncleared spaces. For small farmers, such labor can be economically prohibitive. Moreover, the perennial tree crops that replace monocultured fields of annuals often take years to mature to the point their fruits or nuts can be harvested and sold. A pecan tree, for instance, takes 10 years[xv] to reach full production. Many small farmers dependent on yearly harvests for their livelihoods—especially those in the impoverished Global South—cannot wait that long.
Nevertheless, there are many examples of successful multistrata systems at work—and many of them involve small farmers in the places most vulnerable to climate change.
Successful Examples of Multistrata Agroforestry
In Honduras[xvi], the women-led Cosagual Lenca cooperative[xvii] consists of over 20 female farmers who grow organic, fair-trade coffee under the shade of a variety of fruit and timber trees. While the cafetaleras (female coffee growers) eat most of the plantains, oranges, and pacay fruits they harvest, extra household income comes from selling the leftovers to local markets. Spanish cedar and pine provide not just shade but also wood for building and cooking, while cangrejillo and gurarumo bushes are used to feed livestock and to prepare home medicinal remedies.
Between 2007-09, researchers helped Peruvian farmers in the Ucavali jungle transform land degraded by slash-and-burn practices into homegardens[xviii] that combined fruit and timber trees with vegetable and medicinal plants. After 3 years, 65% of the transformed plots remained: an encouraging sign for the viability of these systems despite the challenges.
As difficult as it is for subsistence farmers to focus on the long-term benefits of multistrata agroforestry, it is in the long game that multistrata agroforestry has the greatest potential to revolutionize the lives of smallhold farmers. As Dean Cycon, owner of Dean’s Beans Organic Coffee and leader in the fair-trade coffee business, notes[xix], growers can harvest and sell timber when they are too old to farm, providing a certain kind of organic “social security” that makes it possible for them to stay on their land even in old age.
Similarly, multistrata agroforestry can enable farmers in Central America to remain in their homelands even when climate change makes conventional agriculture impossible. In 2012-14, a devastating El Niño system resulted in rainfall declining by half in Honduras[xx], forcing many farmers to migrate; in fact, 47% of families in the area farmed by the Consagual Lenca cafetaleras experienced food insecurity that forced at least one family member to emigrate. Dean Cycon points out that the largest group of people[xxi] seeking to cross the U.S.-Mexico border are members of Guatemalan coffee farm families. This is an important reminder that climate change is one of the largest drivers of migration worldwide, and it will only get worse if we neglect to implement crucial agricultural practices in vulnerable areas so that people can make a living in their homelands.
One final point: multistrata agroforestry, like many “nature-based solutions,”[xxii] often draw upon ancient, indigenous land practices. (Cosagual Lenca is an excellent example of this, since they draw upon methods long used by the indigenous Lenca people.) Multistrata agroforestry has such revolutionary potential precisely because it looks back to longstanding successful practices to enable a more sustainable future.
[vi] Drawdown, 47.
[xi] Drawdown, 46.
[xiv] Drawdown, 47.