Maintaining the dietary needs of 7.5 billion people is a balancing act between producing enough nutritious food, keeping the planet from being drained of its biodiversity and natural resources, and providing livelihoods.
According to recent research published in People and Nature, a key pathway to finding this equilibrium lies in tropical trees.
The food industry, of course, is a massive enterprise on every scale. Forty-three percent of land not covered in ice or desert is used for agriculture, which also produces 26 percent of the world’s greenhouse gas emissions. In tropical regions, such large-scale agriculture is a major cause of deforestation.
The agricultural output is enormous but has very little diversity: more than 40 percent of all calories consumed by the world come from rice, wheat and maize. While food is increasingly calorie-rich, fruits and vegetables remain under-consumed in most of the world. Eating fruits and vegetables, as well as nuts and whole grains, can help prevent non-communicable diseases such as cardiovascular disease, diabetes and cancer.
In the seven rural areas located across seven different tropical countries analyzed in this study, tree-sourced foods were key sources of vitamins A and C for residents, and such foods had nine times as much vitamin A and four times as much vitamin C as did other foods.
The fruits, leaves, nuts and seeds of many of the world’s roughly 60,000 tree species are edible and nutritious, but are eaten only locally. Many are unknown to the international market, and some species are not even domesticated. The researchers found that only 34 of the 90 tree-based foods used in their dataset were registered in the trade database of the Food and Agriculture Organization of the United Nations (FAO).
There are many reasons why a food product might not succeed internationally, ranging from its perishability to the way it tastes, says Chris Kettle, senior scientist at the Alliance of Bioversity International and CIAT, lecturer at ETH Zürich and the principal investigator of the study, though he noted that many foods can be dried or stored as a pulp for easier transportation.
“There’s also this sort of global homogenization and aspiration toward Western diets, which means that commodities that are actually not very healthy – and they’re often more expensive – are more favored by communities because they’re perceived as better,” says Kettle.
“The other traditional fruits and products, they’re often seen as old-fashioned foods of the rural poor and not as attractive as some of these other commodities which are imported.”
In addition to nutritional benefits, the study notes the potential environmental benefits from planting tropical trees on farms. Increasing the number of trees on the planet is one important nature-based solution for sequestering atmospheric carbon, as trees are crucial for “soaking up” carbon dioxide released by human activity. A 2010 study found that while only 43 percent of global agricultural land had at least 10 percent tree cover, this already contributed more than 75 percent of carbon storage on these lands, indicating the climate potential of planting more trees on farms, a practice known as agroforestry.
Planting new agroforests, especially on abandoned or degraded landscapes, can be incorporated into large-scale restoration initiatives, such as the Bonn Challenge or Africa’s Great Green Wall. They further provide habitat for certain species and help conserve more diversity of animals, plants and microbes than do monoculture farms. This in turn can enhance ecosystem services such as by enriching the soil and improving water security.
The study also highlights the financial and livelihood benefits for small-scale farmers that planting food trees on their farms can bring. These trees can diversify farmers’ incomes and provide revenue (or just food) during non-harvest seasons for their other crops. The authors noted that some tree species, including banana and papaya, can even produce fruit year-round.
However, the myriad benefits of tropical tree-based food systems depend on a key condition: the biological diversity of the trees. Diverse tree systems use nutrients more efficiently, allowing them to support greater biodiversity of species. Furthermore, wild or semi-wild foods from forests can strongly improve diet quality.
There is a wide gap between these tree systems and the monoculture food tree plantations that have sprouted around the world, such as cacao in West Africa and oil palm in Indonesia. The enormous market demand for such products can lead to deforestation, and thus greater greenhouse gas emissions, in addition to other negativities, such as impacting water security and leaving growers vulnerable to commodity price fluctuations.
The popularization of tree-based food products can also leave behind smallholder farmers, who might not have the financial or labor capacity to scale up production to meet increasing global demand. This leaves more space for powerful actors to use their advantage to succeed on the international market, spurring greater inequality.
Given these risks, what can be done to popularize tropical tree foods while protecting the environment and livelihoods where they are produced? Consumer demand is key here, according to the study. “There are so many foods that are just amazing in and outside of the Amazon that people have never heard of,” says Merel Jansen, a researcher at ETH Zürich and another co-author of the study. For instance, she champions macambo, which is in the same genus as cacao.
“The pulp is great, just like cacao. You can make juices out of it, but the seeds, if you toast them or eat them raw, are very nutritious. It’s starting to become known in U.S. markets a little bit as a superfood,” she adds. “You can mix it in cookies and granola… it’s very tasty.”
To raise demand for these products, the researchers recommended that governments lower taxes on sustainable and healthy foods or raise taxes on unsustainable and unhealthy foods. Various governments have already implemented such policies. For example, since 2014, the Mexican government has levied an excise tax of 1 peso per liter of sugary drinks, which reduced purchases of the taxed drinks by 8.2 percent on average after two years. Authorities can also run campaigns to boost awareness of local tree foods.
But aside from a lack of demand, the long delay between planting trees and harvesting their produce, plus the high initial investments required, might prevent small farms from growing these trees in the first place. The study recommends that smallholders intercrop food-producing trees with suitable annual crops to ensure a steady income.
As for government actors, they could create a system of providing payments for the ecosystem services that the trees support or redirect some of their agricultural subsidies toward the tree-based food industry.
The researchers also strongly emphasize that secure land tenure rights are key to allowing smallholders to invest in growing food trees, particularly since they are long-term investments. According to the World Bank, only 30 percent of the world’s population had a legally registered title for their land in 2017.
The study suggests that protection for land tenure rights could possibly be secured through international and national policies and a robust civil society to ensure the authorities respect these rights. In a project run in Nepal by the International Fund for Agriculture Development, highland families received 40-year renewable leases to plots of severely degraded forests, which they could then manage and protect. By 2009, 69 percent of the forest plots had been rehabilitated, and household incomes had increased by more than 70 percent.
Jansen also notes that domestication might not be necessary for every food-producing tropical tree species, depending on how they are used in food systems. “Many of them can be used really locally, which makes it a lot easier,” she says. “You don’t need full domestication to be able to do that. People can just take some seeds from inputs from the forest, and you don’t need very extensive seed delivery systems.”
Jansen says that establishing sustainable markets is much easier at a smaller, local scale. But international markets also have a major role to play in impacting land use: “There’s much more money available [in the international market], so even though it’s the biggest challenge, to leverage this money in a sustainable way, it also offers large opportunities.”
So what can each of us do individually – even those of us who don’t live in tropical climates – to create a healthier, more sustainable and equitable food system?
“Personally, I think consumption is really, really critical,” says Kettle. He recommends that people eat more plant-based diets and make sure their food comes from fair and sustainable sources.
“Do you only buy chocolate that’s produced in a truly ethical way, where the communities that are producing the cacao are actually benefitting the best, which of course helps to enhance the sustainability of those landscapes,” questions Kettle, “or do you go for the mass-produced, cheap chocolate in which the producers contribute hugely to deforestation?
“Consumption, at the end of the day, is the driving force for all of these land use changes.”
He also emphasizes the importance of selecting imported foods whose transportation has a low carbon footprint. For example, brazil nuts and dried fruit are tropical foods that don’t perish so quickly and can be transported more efficiently. “No one’s suggesting we should all be going out and buying air-freighted rambutan,” he says.
Jansen recommends that consumers also dabble in producing their own local products, such as by growing their own trees and gardens, even in temperate regions.
“Let’s all just get out and explore, get out of our comfort zones and see what else we can eat and grow.”