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Mixing trees and crops can help both farmers and the climate


Maxwell Ochoo’s first attempt at farming was a sad failure.

In Ochieng Odiere, a village near the shores of Lake Victoria in Kenya, “getting a job is a challenge,” says the 34-year-old. To make money and help feed his family, he turned to farming. In 2017, he planted watermelon seeds on his 0.7-hectare plot.

Just as the melons exploded from their buds and the balloon into succulent spheres, it produced a two-month dry spell and Ochoo’s new watermelons withered. He lost about 70,000 Kenyan shillings, or about $ 650.

Ochoo blamed the region’s tree loss for the long dry spells that had become more common. He says the sun is not protected, the ground is cooked.

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In 2018, Ochoo and some residents decided to plant trees on public land and small farms. With the help of non-profit groups, the community planted hundreds of trees, turning some of the barren slopes green. On his own farm, Ochoo now practices calella cultivation, in which he plants corn, onions, sweet potatoes and cassava among rows of fruit and other trees.

Trees provide shade and shelter to crops, and their deeper root systems help the soil retain moisture. Sometimes a week during the growing season, Ochoo takes to the market papayas, some as big as the head, bringing home the equivalent of about $ 25 each time.

And the fallen leaves of the new Calliandra trees provide fodder for the five Ochoo cows. He also discovered that he could grind fern-like leaves as a dietary supplement for tilapia grown in a small pond. He now spends less on fish food and tilapia grows much faster than his neighbors ’fish, he says.

Today, almost everything the Ochoo family eats comes from the farm, leaving much to sell in the market. "Whether during the dry season or the rainy season, my land is not bare," he says, "there is something that can sustain the family."

a crouched Kenran farmer and papaya snack Maxwell Ochoo eats a juicy papaya from his farm in Kenya. Papaya trees help keep moisture in the soil in drier seasons, benefiting the crops it grows among the trees.M. Ochoo

Ochoo’s tree-filled farm represents what many scientists hope will be the future of agriculture. The current reality, where fields are often cleared of trees to raise cattle or plant row after row of individual crops, called monocultures, is running out of space.

About half of all living land is devoted to food cultivation. More than 30 percent of forests have been cleared worldwide and another 20 percent have been degraded, largely to make room for livestock breeding and cultivation. By 2050, to feed a growing population, farmland will have to increase by 26 percent, an area the size of India, researchers estimate.

The collective hunger of human beings leads to the twin ecological crises of climate change and the loss of biodiversity. Cutting down trees to make room for crops and livestock releases carbon into the atmosphere and erases the natural habitats that support so many species (SN: 1/30/21, p. 5).

Humanity is in danger of crossing a planetary boundary with unpredictable consequences, says landscape ecologist Tobias Plieninger of the German University of Kassel and the University of Göttingen. As land continues to be cleared for agriculture, "there is high pressure … to shift to more sustainable land use practices."

Farmers like Ochoo, who intentionally mix crops, trees, and livestock, a practice vaguely called agroforestry, offer a more sustainable path. The agroforestry may not work in all circumstances, “but it has great potential,” Plieninger says, to work toward food production and conservation goals on the same land.

two cows are near some treesIn an agroforestry project, cows graze among apple trees in a vegetable garden in Poland.AGFORWARD / FLICKR PROJECT (CC BY-NC-SA 2.0)

Integrating trees on farms may seem like a recipe for lower yields, as trees would replace some crops. But that mixture can squeeze more food out of a given plot than when the plants are grown separately, Plieninger says. In Europe, mixed farms growing wheat or sunflower between rows of wild cherries and walnuts, for example, can produce up to 40 percent more than monocultures of the same crops for a given area.

Agroforestry was the norm until modern agricultural methods swept the planet, especially after the Industrial Revolution and the rise of chemical fertilizers in the mid-20th century. But the small farms in the tropics are still big in the trees. Worldwide, about 43 percent of the land used for agriculture has at least 10 percent tree, according to a 2016 study in Scientific Reports.

In Europe, mixed farms growing wheat or sunflower between rows of wild cherries and walnuts, for example, can produce up to 40 percent more than monocultures of the same crops for a given area.

Increasing that percentage can have profound and broad benefits, if done right. “Trees have to be integrated (on farms) so as not to create additional problems” for farmers, says Anja Gassner, a senior scientist at World Agroforestry in Bonn, Germany. And the approach seems very different depending on the region and the goals of the people who live there. What Spanish farmers need from their oak fields where pigs fatten on acorns will be different from what Ecuadorian farmers want from their coffee plants that grow under the cool shade of tropical inga.

The way agroforestry is carried out in three very different parts of the world illustrates the promises and challenges of coupling trees and crops.

Made in the shade

If you’re drinking a cup of coffee in the morning while reading this, there’s a possibility that the beans come from farms that practice agroforestry.

Coffee plants have evolved in the understory of the forests of the mountains of Ethiopia; they are very suitable for shade, says Eduardo Somarriba, agroecologist at the Tropical Agricultural Agricultural Research and Higher Education Center in Carthage, Costa Rica.

a green field with coffee plants planted in rows between treesRows of coffee plants are shaded by trees on this plantation in Ecuador. Trees help prevent slopes from eroding and can be harvested to provide farmers with additional income.Morley Read / Alamy Stock Photo

A diverse canopy of native trees can help coffee plants thrive. Somarriba says certain trees pump nitrogen into the soil, eliminating the need for intensive fertilizer application. Native vegetation suppresses weed growth, stabilizes soil and temperature, improves water retention, and supports pollinating animals.

But as the world’s coffee headquarters grows, planting practices have shifted to shady plots filled only with coffee plants that require a steady stream of chemical fertilizers. From 1996 to 2010, the global share of coffee grown under a canopy of various trees fell from 43% to 24%, researchers reported in 2014 in BioScience.

Tree removal is good for increasing yield, although the evidence is mixed. This focus on the figures misses the most diffuse benefits of diversifying farms, says Somarriba, especially small ones, which still produce most of the world’s coffee.

From 1996 to 2010, the world share of coffee grown under a canopy of various trees fell from 43% to 24%.

“If coffee prices go down and stay low for five or six years, a small farmer won’t be able to do it just by (selling) coffee,” says Somarriba. But adding a mixture of trees can increase economic and climate resilience, he says.

Valuable woody trees, such as mahogany, can serve as savings accounts, harvested when the benefits of coffee are not enough. Mango, Brazil nuts or acai trees can also provide income. But not all places have well-developed markets for these products, says Somarriba, which poses a challenge to increasing the share of coffee grown under shade.

Some conservationists are trying to increase consumer demand for shade-grown coffee by highlighting how it benefits biodiversity. The Smithsonian Migratory Bird Center, for example, grants Friendly Bird certification to plantations with extensive coverage and native tree diversity, a blessing for migratory birds. Certified farmers can charge a slightly higher price, averaging between 15 and 15 cents more per kilo.

Migratory birds come to these plantations. “When you’re on a coffee farm that supports birds, it looks like you’re in the woods,” says Ruth Bennett, an ecologist at the Smithsonian Migratory Bird Center in Washington, DC. “You hear a lot of bird calls, and it’s a huge diversity of birds, including very sexy tropical species like the turquoise sky motmot,” she says.

Bird-friendly coffee plantations also seem to be good for mammals. In Mexico, bird-friendly coffee plantations had more native wildlife, including deer and mice, than other coffee plantations, according to a 2016 study in PLOS ONE.

Ecosystems filled with various species of plants, animals and more make the planet habitable by filtering water, circulating nutrients through the soils and pollinating crops. Although undeveloped forest is clearly best for biodiversity, shade-grown plantations can outpace other land uses. After more than a decade, high-diversity coffee agroforestry systems in southeastern Brazil were ecologically healthier – measured by tree canopy cover and species richness – than plots reserved for non-agricultural restoration, researchers at Ecology reported. September 2020 restoration. About 90 percent of the canopy was intact in shaded coffee plots compared to 60% in restored forest areas, on average.

Beyond the benefits to biodiversity, Bennett says coffee grown in the shade only tastes better. Under shade, coffee cherries take longer to develop, which can increase the sugar content.

Recovery time

In the Shinyanga region of Tanzania, a return to traditional indigenous practices, with a dose of modern agroforestry, has helped transform what was once the “Tanzanian desert” back into productive savannah forests.

The region, about a five-hour drive southeast of the Serengeti, is home to the Sukuma people, traditionally pastoralists who raise cattle in the region’s mountain meadows, dotted with acacia and oak-like worms.

But in the 1920s, the landscape began to change. The British colonial government cut down forests in a misguided effort to control tsetse flies that were harming livestock and humans and planting economic crops such as cotton. In the 1960s, forest loss accelerated when the government took ownership of many estates. After losing the rights to harvest forest products, local Tanzanians had fewer incentives to conserve the trees.

Within a few decades, the ecosystem degraded into dry, dusty, treeless expanses. Food, firewood and water were scarce and local livelihoods were suffering, says Lalisa Duguma, a sustainability scientist at World Agroforestry, an international research agency based in Nairobi, Kenya.

In the 1980s, the situation became so serious that the Tanzanian government intervened. At first, he tried to convince area residents to plant seedlings of fast-growing exotic trees, such as eucalyptus, Duguma says. But the residents were not interested in planting or caring for those seedlings. Faced with this setback, experts and officials have done something that has not always been done in development projects: they have listened.

"With only fencing on degraded terrain, the restoration process begins."

Lalisa Duguma

Listening to the locals revealed that an ancient tradition of forming ngitilis could be the basis for restoration. Roughly translated as “enclosure,” a cord ngitili of a section of land for one or two years, allowing trees and grasses to recover and then open to provide fodder for grazing animals during the dry season. “By just fencing off degraded land, the restoration process begins,” Duguma says.

Native seeds and stumps long atrophied by grazing or poor soil conditions may begin to grow again, and their numbers may be supplemented by planted trees. Local institutions largely planned and supervised the ngitilis, in accordance with traditional practices, often in collaboration with government scientists.

Year after year, the benefits of ngitilis have been slowly accumulating, giving shade and fodder to livestock and wood for energy and building. Ripening trees provided fruits and hives for honey production.

At the beginning of the restoration in the mid-1980s, there were only 600 hectares of ngitilis in the entire Shinyanga region. After 16 years, more than 300,000 acres of land have been restored. The return of trees in the region may have hijacked more than 20 million metric tons of carbon over 16 years (the equivalent of taking 16.7 million cars off the road in a year), according to a report by the Tanzanian government and the International Union of 2005 for Nature Conservation. Deeper root systems enhanced soil health and expanded tree cover reduced wind and water erosion, halting desertification.

dry land in the Shinyanga region in TanzaniaAfter decades of cutting down trees, the landscape of Tanzania’s Shinyanga region has dried up.Dr. Otsyina

a green landscape with green-covered land and treesIn the 1980s, the focus on creating plant reserves called ngitilis transformed the landscape.L.A. Duguma / World Agroforestry

Ngitilis provided benefits equal to $ 14 per person per month, substantially more than the $ 8.50 a person spends in a month in rural Tanzania, according to the same report. The money from community ngitilis was earmarked to improve housing, Duguma says.

Biodiversity has flourished as well. Ngitilis collectively housed more than 150 species of trees, shrubs, and other plants. With habitat restored, people in the region began to hear the cries of hyenas at night, a welcome return, Duguma says. At least 10 species of mammals returned, including antelopes and rabbits, and 145 species of birds were recorded within the ngitilis.

There is a huge need to expand this type of community-led success across Africa, where about 60 percent of agricultural land is degraded, says Susan Chomba, who led the Regreening Africa initiative before becoming director of Vital Landscapes at World Resources Nairobi Institute. . Regreening Africa, an ambitious 2017 initiative led by World Agroforestry, hopes to reverse land degradation in one million hectares of sub-Saharan Africa by 2022 to improve the lives of people in 500,000 homes.

There are many drivers of land degradation, “but the underlying problem is poverty,” Chomba says. If a woman can feed her children just by cutting down a tree to sell firewood, her choice is clear, says Chomba. To offer better options, Regreening Africa hopes to combine agroforestry and sustainable land use practices. The goal is to generate revenue for local residents by restoring the landscape.

"If I am planting a tree that will take years to grow and I am not guaranteed ownership of that tree or land, what is my incentive to invest in it? Restoration efforts must come together to guarantee land rights."

Susan Chomba

The key to that goal is close collaboration with local people. Some farmers may want to restore water in a region that once had streams, or people may want shea trees to make profitable shea butter, Chomba says. He says tree planting schemes that include preformed ideas of what a region needs, without getting involved and listening to the local community, will not go far.

And land use policies are key to resident entry, Chomba says. In Africa, “we came from a history of colonialization,” he says. As a result, much of the land that is wooded or that could be restored by farmers is state-owned. Because trees are often state-owned, it is difficult for residents to profit from the sale of fruits and other tree products.

"If I'm planting a tree that will take years to grow and they don't guarantee me ownership of that tree or land, what's my incentive to invest in it?" Chomba asks. "Restoration efforts must unite to secure land rights."

The basket of the United States

In the United States, thoughts about agriculture probably evoke images of Iowa’s endless cornfields or massive pig farms. Although industrialized monoculture is the norm among large players, small farmers are better able to incorporate trees into their fields or bring crops to forests.

According to the 2017 Census of Agriculture by the U.S. Department of Agriculture, of the approximately 2 million U.S. farms, only 1.5 percent reported practicing some form of agroforestry. This percentage is likely to be underestimated, but experts say it reveals how much space there is to grow.

Agroforestry practices vary across the United States. In the Midwest, trees serve as windbreaks for crops and streams to minimize runoff of fertilizers. In livestock, ranchers plant honeycombs on their pastures to provide shade during the summer and nutrient-rich pods that feed the animals. Forestry, where non-timber crops such as wild mushrooms or ginseng are grown in a managed or wild forest, is becoming more popular in the eastern states.

Agroforestry involves breaking down the wall between farmland and forests and mixing them, says John Munsell, a forest management researcher at Virginia Tech in Blacksburg. “It’s a way of thinking creatively through a landscape,” he says. Often, small farmers are more likely.

Anna Plattner and Justin Wexler practice forestry, growing shiitake mushrooms on logs in wooded areas and picking wild golden oyster mushrooms (shown) to sell at local farmers markets and restaurants.Courtesy of Wild Hudson Valley

Anna Plattner and Justin Wexler had to be creative to support their farm in New York’s Hudson Valley. The 38-hectare farm cultivates heritage plants used by the Mohican peoples and indigenous munsees of the region. The farm also incorporates traditional agroforestry methods, Wexler says. The rows of pawpaw and persimmon are staggered among the native varieties of corn, beans and pumpkin. The farm also grows darker foods, including hopniss, a legume that was a staple food for some Native American tribes before the arrival of Europeans.

Wexler says he hopes focusing on the food of indigenous peoples can help others learn about the history and culture of the area. Demand for these unknown crops is not high, so in addition to selling to wholesalers and restaurants, this year Plattner and Wexler were launching monthly "wild harvest boxes," a kind of local blue apron for local produce. The boxes come packed with snippets of story about food and recipe ideas. “Each plant has its own story to tell,” Plattner says.

Small farms may be more willing to adopt agroforestry, but to meet the challenges posed by climate change and biodiversity loss, large farms also need it.

In the United States, “there is enormous potential to increase agroforestry,” says agroecologist Sarah Lovell, director of the University of Missouri Agroforestry Center in Columbia.

For Lovell, the first step involves identifying marginal areas on farms where trees could be planted with minimal disruption to the status quo, such as along streams. Putting trees around waterways can reduce flooding and erosion, improve water quality, and harbor wildlife, Lovell says. In the “true Midwestern bakery,” he estimates, only 2 to 5 percent of these areas are currently making use of trees.

Finally, he says he would like to see a drastic expansion of alley cultivation, with lines of fruit trees or nuts fully integrated into the fields. Lovell says the need to move fruit and nut production eastward, away from California increasingly affected by drought, could provide an additional impetus to bring more trees to monoculture farms.

But corn and soybean fields dominate much of the farmland in the United States. These lucrative crops serve as raw materials for everything from biodiesel to high-fructose corn syrup. To convince farmers to replace some of these crops with trees, the fruits of those trees will have to be more common. The Savanna Institute, an agroforestry nonprofit in Madison, Washington, is focused on expanding the chestnut and hazelnut market.

“We call them corn and soybeans in the trees,” says Savanna Institute ecologist Kevin Wolz. Chestnuts are about 90 percent starchy, like corn; hazelnuts are 75 percent oil and protein, like soy, Wolz says. Researchers at the institute are discovering how these tree products could replace corn and soybeans as raw materials in production pipelines, with rows of nuts breaking up monoculture fields. “We think these could be the next commodity harvests the Midwest can produce,” Wolz says.

It remains to be seen whether we will soon take soft drinks sweetened with chestnut syrup. But to transform agriculture from a climate change problem to a solution, Wolz says such bold and imaginative thinking is essential.

Agroforestry is not a silver bullet for tackling climate change, the biodiversity crisis, or food insecurity, Wolz says. But when applied thinking about the place and the people, it says it can be a Swiss Army knife.

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