Made in the shade
There’s a bonus to growing coffee in a traditional way that preserves tall trees — and it’s not just for the birds.
Scientists recently found a rich and diverse bird population living in the shade of forested coffee farms. Those farms are in the east African nation of Ethiopia. Ample birdlife is just one of many benefits of this type of farming, called agroforestry. The practice mixes in trees when growing crops or raising livestock.
Combining forest and farm provides habitat for many species of wildlife around the world. The practice can help keep waterways clean and soils healthy. This helps farmers and ranchers. Agroforestry is essential to producing one of the world’s favorite treats — chocolate. And it may even blunt the effects of climate change.
Thanks to growing recognition of its benefits, this ancient farming technique is gaining new attention.
In Ethiopia, agroforestry has been the standard way to grow coffee for more than a thousand years. The coffee plant, Coffea arabica, thrives in the shadows of tall trees. (The word “coffee” comes from the name of an old Ethiopian province named Kaffa.) To farm coffee, growers simply thin the forest of any competing plants. Experts prize the resulting shade-grown coffee beans.
An Ethiopian coffee farm is “a gorgeous forest with massive, old-growth trees in the canopy and these coffee plants that are a native species growing in the understory,” explains Evan Buechley. He’s a graduate student at the University of Utah in Salt Lake City. Buechley studies birds and conservation biology.
Buechley and his colleagues recently conducted a census of birds on Ethiopia’s farms and in its forests. His team found something special: All the species of birds that could be found in the forest also were living on traditional coffee farms.
Despite its benefits, many farmers are reluctant to adopt agroforestry practices, says Jim Brandle. He is a professor of forestry at the University of Nebraska-Lincoln. People have a difficult time believing it’s worthwhile planting trees on land that could be sown with a profitable crop, he explains. Still, the idea is catching on. India, for example, announced in 2014 that agroforestry would lead its push to add more trees.
Long before the technique got its name, humans had used agroforestry to grow plants. The basic idea behind agroforestry is the same, Brandle explains, whether it’s in Africa or halfway around the world in the South Pacific. On Hawaii and other tropical islands in the Pacific Ocean, for instance, farmers have a history of cultivating forests filled with coconut, banana, breadfruit and other trees. Agroforestry is also common elsewhere, even in the continental United States.
If you travel across America by car, bus or train, you’ll pass a lot of farms. You might see field after field of corn in Indiana, barley in Montana or soybeans in Iowa. In many places, a thin wall of trees will border a field. It’s called a windbreak. Although this looks very different from an Ethiopian coffee farm, windbreaks represent a form of agroforestry.
In fact, windbreaks may be one of the most easily recognizable forms of agroforestry in the United States. Planting trees along the edges of a field interrupts the wind, altering its speed, Brandle explains. Next to a windbreak, it’s a little warmer and less windy. Crops grow better in these sheltered areas. The trees also help to protect the soil from wind erosion.
Another common type of agroforestry in the United States takes place along what are called riparian (Ry-PAIR-ee-un) zones. These are regions along the banks of rivers and streams (ripa is Latin for river bank). To create a buffer — or protected area — farmers plant trees and other types of vegetation here. This vegetation helps limit erosion. The plants also provide food and habitat for birds and other wildlife. And the greenery helps prevent rains from washing sediment, nutrients and pesticides away into nearby streams.
In the Midwest, where Brandle works, “we’re trying to reduce the amount of [this] runoff that comes off of the crop fields and goes into the local stream,” he says. Once it reaches a river, that pollution can flow all of the way to the Gulf of Mexico. There, excess nutrients carried by the water can promote a formation in the Gulf of dead zones. These are large areas of open water where there is temporarily too little oxygen for sea life. Some affected animals can essentially suffocate.
Sometimes, Brandle says, it can be difficult to convince farmers that planting a windbreak or a buffer is a smart move. “There’s the perception that they take land out of production. And they do,” he admits. Still, farmers don’t always recognize the gains that can come from giving ground to more trees.
And it can take time to see those benefits. Unlike many crops, trees take a while to grow, notes Florencia Montagnini. She studies the sustainability of forests and agroforests. She is a research scientist at Yale University in New Haven, Conn. To convince people to plant trees, “what you have to do is show them the benefits of it.”
Sunny prospects for shaded farms
Money can be one of the benefits of agroforestry. It’s something farmers and ranchers appreciate. To earn more, some farmers combine trees with livestock and forage — those plants that the grazers eat. This is yet another type of agroforestry, called silvopasture. (The word combines the Latin word for forest — silva — with a term that describes land grazed by animals.) This practice is often found in the southern United States.
“By managing how many trees are out there in a given area,” Brandle says, “we can regulate the amount of light that reaches the surface.” With too much shade, nothing will grow beneath the trees. “But in a silvopasture system,” he says, “what we’re doing is opening up that canopy until we find a nice mix that gives us a reasonable timber [harvest] at some point in the future and an annual crop of forage.”
Raising cattle and growing trees on the same land doesn’t just provide two sources of income. It also protects against losses in a bad year. If timber prices fall too low in one year, a farmer can wait to harvest the wood and rely on just the cattle for profit.
Cows also benefit from grazing in pastures that provide shade. That is especially important in warm parts of the world, notes Montagnini. These animals can get overheated out in the sun. When that happens, cattle don’t gain as much weight, make as much milk or birth as many calves. “Very often the trees are something that you need for the cattle to produce more,” she says.
And cows aren’t the only organisms that suffer from too much direct sun. Plants need sunlight to grow and thrive. But excess sun can bake tender leaves and dry out the soil. Plenty of tropical species that end up on our plates grow better in the shade, notes P.K. Nair. He studies agroforestry at the University of Florida in Gainesville. The quality of plants such as coffee, black pepper and vanilla all improve when they are planted in the shade of trees, he says. The same goes for the cacao tree. Its beans are the key ingredient in chocolate.
Some farmers will grow coffee or other shade-loving crops in the direct sun because they can fit in more plants. But they often produce a lower quality product. And these less-healthy plants may need chemical pesticides or fertilizers that shade-grown crops wouldn’t. People may be willing to pay high prices for varieties grown in the shade to avoid those chemicals. In Ethiopia, Buechley notes, coffee grown in the shade can bring in $310 more per hectare (2.47 acres) than the same crop grown in full sun.
Benefits for the planet
Agroforestry’s benefits for farmers and the local environment are well known. But now scientists and world leaders think that the practice can do a lot to lessen the impact of much bigger problems. Among them: deforestation and climate change.
In recent years, people have been removing trees from the landscape at an alarming rate. Between 1990 and 2005 alone, people removed more than 16.2 million hectares (63,000 square miles) of forests, reports the United Nations Food and Agriculture Organization. That area is almost as large as the state of Florida.
And the situation is getting worse. Scientists had thought that the rate of deforestation was slowing in the humid tropics. Such areas include the Amazon in South America. But a recent analysis found that the loss of forests in these areas actually sped up by 62 percent between 1990 and 2010. The finding comes from a study published May 16 in Geophysical Research Letters.
Agroforests are not perfect replacements for natural forests. Consider those Ethiopian coffee farms.
Utah’s Buechley and his colleagues trekked each day for weeks to a new spot on a coffee farm or remote Ethiopian forest. They would spend the afternoon setting up a fine mesh that traps birds without harm. Early the next morning, before sunrise, the researchers returned and unfurled these mist nets. Then they identified and measured each captured bird. They also attached a numbered band, called a tag, to each bird before releasing it.
“People have done a lot of research on coffee farms in different parts of the world,” Buechley notes. In many places, forest birds and other animals don’t survive well on farms, even ones that practice agroforestry. In Ethiopia, though, all of the forest species of birds also lived on the coffee farms. But many specialist birds declined in number. These are species that live in only a narrow set of circumstances.
“They didn’t vanish… but their numbers declined by about 80 percent compared to nearby forest,” Buechley says. His conclusion: While shade-grown coffee is a big improvement over most other forms of agriculture, it is not the same as a natural forest. His team’s study appeared February 11in Biological Conservation.
Agroforestry, however, can be a compromise between unnatural fields covered with a single species of plant and the original forest landscape, notes Montagnini at Yale. “Putting trees back on the land would be a way of harmonizing things,” she says. By that she means that those trees can perform several tasks that are good for the environment. These include maintaining habitat for a diverse range of organisms.
India now recognizes agroforestry as perhaps the only way to meet its target of rebuilding forests. The country wants to increase its tree cover to 33 percent. Currently, trees cover less than 25 percent of India.
More trees could also help a global problem — climate change. Largely through burning fossil fuels, people have been emitting lots of carbon dioxide and other greenhouse gases. These gases trap heat in the atmosphere, warming it. Recently, that warming has reached troubling levels. But trees soak up some of that carbon dioxide from the air, notes Montagnini. And trees sequester, or lock up, that carbon dioxide for years.
Farms that grow a single plant crop — such as corn or wheat — don’t sop up as much carbon. Farming practices such as agroforestry, that grow multiple species, could lock up more of the gas, Nair says.
And worldwide, whether it’s a windbreak in Wisconsin or a cocoa farm in Costa Rica, Montagnini notes, “increasing the amount of trees on the land is something that can be achieved.”