Food trees for nutrition and health
Food and nutritional security remains one of the most pressing challenges of our time, and requires the promotion and use of innovative agricultural interventions for long-term, sustainable benefits and outcomes. Currently, about 1 billion people, most of them in low-income countries, are food and nutrition insecure. Many of these people lack the quality and quantity of food that is necessary for an active and healthy life. In addition, an estimated 20% of the population in developing countries suffers from micronutrient deficiencies
Trees are a critical component in the quest for food and nutritional security. Indeed, tree products have always been an important part of people’s diets – from early humans gathering of fruits and nuts, to the domestication of important varieties of fruit trees, such as mango (Mangifera indica), which has been cultivated in India for over 4,000 years. Aside from their nutritional value, tree food products are important in the economic growth and development of many countries of the world, particularly in the tropics.
The rising local and global demand for horticultural produce creates opportunities for income generation through the cultivation of fruit-, nut- and vegetable-producing trees, benefiting small-scale farmers, entrepreneurs and a range of players in the associated value chains.
Examples of important tree food product
Allanblackia genus, a group of tree species found in several African countries, is an important group, whose seeds contain fats that are excellent for a number of food applications. Indeed, the exceptional characteristics of allanblackia oil have been recognised by the food processing industry, and use is being made of it as a new ingredient in the sustainable manufacture of margarine and other products. The potential market demand for the oil is estimated to be over 100,000 tons per year.
In an effort to help develop the sustainable production of oil from the seeds of Allanblackia species in equatorial Africa, the World Agroforestry Centre (ICRAF) has engaged in a public-private partnership with Unilever and a collection of public non-profit organizations, called the Novella Africa Initiative. The partnership has developed a model for over 10,000 collectors or growers of Allanblackia to plant over 20,000 seedlings in Ghana, Nigeria and Tanzania.
Baobab (Adansonia digitata), also known as mbuyu, or the African baobab is a huge wild fruit tree occurring in the drylands of Africa. This tree produces a naturally dehydrated fruit pulp which has five times the vitamin C content of oranges. It also contains vitamins A, B1, B2 and B6, as well as several minerals, including calcium, phosphorus, potassium, iron, sodium, zinc and magnesium.In addition, its seed yield an oil that is said to contain omega 3, 6 and 9 fatty acids. The leaves as well as young stems and roots are eaten as vegetables, and are high in protein, vitamin A and iron.
Moringa oleifera, commonly known as moringa, drumstick, or horseradish tree is the most widely cultivated species of the Moringaceae family.The tree, which originated from India and Arabia, grows in harsh climates and poor soils and is nowadays widely cultivated in tropical and subtropical areas around the world.Moringa is recognised for its multiple uses, including for food, medicine, fodder, water purification, fencing and fuelwood.Its edible parts include leaves, pods, flowers, seeds and roots. The tree’s leaves are the most nutritious, as they contain substantial amounts of macro- and micronutrients, especially protein, provitamin A, vitamin C, folate, calcium and iron.The nutrients in the moringa leaves are comparable and in some case even superior to other foods known to be high in them.
For example, the provitamin A content of fresh moringa leaves is similar to that in carrots and is highest among a range of tree leaves, for instance those from Adansonia digitata (baobab) and Tamarindus indica (tamarind).
In comparison to cow milk, moringa leaves contain twice the amount of protein and up to four times the amount of calcium.
Many other products from tree nut species provide fats and oils that are nutritionally important, not least because they facilitate the absorption of vitamins A, D and E. Macadamia integrifolia (macadamia nut), for example, is rich in oil, proteins and carbohydrates. It is also a good source of Vitamins B1, B2 and E, and of fibre, calcium, phosphorous, magnesium, iron and potassium. Its nuts can be eaten raw or roasted. They can also be used to make edible oils and confectionery products.
Other important oil and nut trees include coconut (Cocos nucifera), cashew nut (Anarcadium occidentale), the mongongo nut (Ricinodendron rautanenii), pistachio (Pistacia vera) and Brazil nut (Bertholletia excelsa), which are all important to people’s diets in many different cultures and form the basis for multi-million dollar industries.
Areas for further research
In all of the above cases, genetic variation within species can be exploited to increase yield and quality. In allanblackia, for example, a more than four-fold difference in average seed yield per fruit has been observed between trees within wild populations of one species of the genus. In semi-domesticated safou (Dacryodes edulis), another important African fruit, at least five-fold variation in the economic value of the fruit is observed between different cultivated types. Studies to characterize such variation are relatively limited, but there is clearly much potential for the genetic improvement of many little-researched tree fruits and nuts.
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Trees for fodder
In low-income countries, livestock keeping is extremely important as a pathway towards poverty alleviation and nutritional security for millions of people. Trees can play a significant role in addressing some of the factors that limit the sustainability and productivity of livestock.
One of the key challenges is the availability of high quality fodder. Currently, most fodders used in developing regions are derived largely from grasses and crop residues such as sorghum, maize, pearl millet and rice. This feed is bulky, high in fibre and low in nitrogen and minerals, and animals are often unable to consume it in large quantities and to digest it properly. In addition, farmers cannot afford to regularly purchase often expensive feed supplements to satisfy the animals’ nutritional requirements.
The role of trees in fodder production
Trees also have a major role in addressing a range of adverse impacts on livestock keeping that are likely to be caused by climate change. The expected variations, in temperature, reduced rainfall and generally more variable weather conditions, will probably lead to decreases in feed quantity and quality.Because tree fodders have deep root systems that can draw water from further into the soil, they are more resilient to variability in weather patterns. Therefore, they can provide fodder for longer than shallower-rooted plants during dry periods.There are many protein-rich trees and shrubs with leaves, fruits and seed-pods edible to livestock, and can be used as high-quality fodder supplements
Examples of agroforestry for fodder interventions in East Africa
In the last three decades, new agroforestry approaches have emerged in East Africa, involving the planting of mostly-exotic tree fodders, with calliandra (Calliandra calothyrsus, a leguminous species) being the most popular.Farmers in the highlands are using calliandra as a substitute for dairy meal or as a supplement to a basal diet that includes crop residues, Napier grass and natural grasses. One kilogramme of dried calliandra leaf is estimated to contain an amount of digestible protein that is similar to that of dairy meal.For each dairy cow, a farmer needs approximately 500 calliandra trees to provide sufficient feed throughout the year, although the majority of farmers plant fewer than this. Normally, calliandra is ready for first pruning for fodder nine to 12 months after initial field establishment, and the trees can be pruned four or five times a year.More than 200,000 small-scale dairy farmers in the highland regions of East Africa are growing calliandra, normally planting it along field boundaries, where it does not compete with crops, and along contours, where it helps to limit soil erosion.
Challenges, recommendations and areas for further research
To design and implement more effective tree fodder agroforestry systems, challenges that need to be addressed through further research include
- Potential for improved productivity not only comes from the use of the right fodder tree species, but in exploiting the genetic variation in fodder production characteristics that occur within species.
- Calliandra, for example, demonstrates large differences in leaf production and leaf digestibility among provenances that could be very usefully exploited to improve value.
- Genetic variation in fodder production and quality for most trees and shrubs has not been widely studied and more work is required.
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Trees: nature’s pharmacies
Since ancient times, plants have been an important source of preventive and curative medicines for people and their livestock. Today, about an eighth of the 422,000 plant species documented worldwide are reported to have medicinal value, and many thousands are used for medical purposes. The trade in medicinal plant products provides income and employment to millions of people living in low-income nations. The global market for herbal medicines is estimated to be worth USD 40-60 billion annually, growing at an annual rate of 7-10%.The therapeutic effects of medicinal plants arise from the chemical properties of their secondary metabolites. Therefore, as well as being important as medicines in their own right, plants are rich sources of novel bio-active compounds for the pharmaceutical industry.The global market for herbal medicines is estimated to be worth USD 40-60 billion annually.Indeed, about 25% of drugs in the modern pharmacopoeia are derived from plants, and many others are synthetic analogues built on prototype compounds isolated from plants.
The role of medicinal plants
Medicinal plants have, for example, played an important role in the treatment of malaria for centuries. Since at least the 15th century, local people in South America, and then the Spanish (after their arrival a century later), recognised the potency of the bark of the local Cinchona ledgeriana (Quinine bark) tree, which contains quinine, as an antimalarial.Various synthetic analogues of quinine have since been developed for malaria treatment. The use of artemisinin extracts from the Artemisia annua (artemisia) shrub – especially of artesunate, artemether and dihydroartemisinin – is another example of a plant-based treatment for malaria.Originally used in China, this shrub has become increasingly important worldwide in recent years, in the production of artemisinin-based combination therapies against malaria.Approximately 80% of people in developing countries still rely on traditional medicines for their primary health care needs
Despite immense progress in modern medicine, approximately 80% of people in developing countries still rely on traditional medicines for their primary health care needs, and the treatment of animals with traditional medicines also remains very high.It is often the poor in societies that particularly rely on traditional medicines. In part, this is due to inadequate access to, and the high cost of, ‘formal’ health care and veterinary services, but it is also due to traditional – as well emerging – beliefs in the value of herbal medicine.Several countries, including Cuba, India, Sri Lanka and Thailand, have endorsed the official use of traditional systems of medicine in their health care programmes. For example, the Ayurveda, Sidha and Unani Indian systems of medicine depend entirely on plant materials or their derivatives for treating human ailments.
Some Important medicinal plants
Prunus african (African cherry) is one of the most important medicinal trees globally which has been used for the last 35 years in the treatment of benign prostate disorders in men. Prunus africana is also used in many African households to address a variety of other ailments.Prunus africana is native to the montane tropical forests of Sub-Saharan Africa and Madagascar,occuring wild in forests in the Eastern and Southern Africa regions Prunus africana is also used in many African households to address a variety of other ailments. The tree has now been widely planted by smallholders, especially in Cameroon, and harvesting of this resource could take pressure off natural stands.Moringa oleifera, commonly known as moringa, drumstick or horseradish tree, has many medicinal uses. For instance, it is used as a natural antibiotic, an aid in childbirth and for treating liver disorders.In Oman, moringa oil is used to treat stomach disorders. In Haiti, villagers boil the flowers in water and drink the tea as a powerful cold remedy. Dried moringa leaves are used to treat diarrhoea in Malawi. In addition, the tree’s seed contain natural coagulants which can clear turbid water and eliminate up to 99% of bacteria.Warburgia ugandensis is another example of an important African medicinal tree. This tree is significant within traditional health systems for curing several ailments in humans including stomach aches, constipation, toothache, common cold, cough, fever, muscle pains, weak joints, measles and malaria.It is also widely used for treating a wide range of animal ailments. The tree’s efficacy is linked to its antibacterial and antifungal activities, which have been scientifically proven in various trials.
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Challenges, recommendations and further research
One of the main challenges is unsustainable harvesting. In many cases, harvesting for medicinal purposes, for instance of bark and roots, can lead to the death of trees.Some herbal medicines have been known to cause serious adverse reactions, with some containing chemicals that may produce long-term side effects, being carcinogenic and hepatotoxic. Herbal medicines must be used appropriately, which means that good quality control and standardisation procedures are essential.It is also vital to safeguard traditional knowledge and practices, which have been passed on orally among traditional medicine practitioners for many generations. Currently, the displacement of people from traditional lands and changes in family structures are affecting the effective transmission of this knowledge.
Timber: from Forests to Farms
Timber is an important commodity in low-income countries, with its demand increasing at the local, regional and international levels. Previously, timber was largely exported from low-income nations to the European Union and United States of America. However, in recent decades, several countries of the South, among them Brazil and China, have become major importers, opening up new markets for producers in low-income regions. In addition, there is a fast growing requirement for wood products in the domestic markets of many other countries in developing regions.
For a long period, timber in low-income countries was harvested primarily from forests or from privately owned plantations. However, these sources are no longer able to meet rising consumption sustainably. In several countries, conservation, environmental and social concerns have led to bans on the harvesting of timber from natural forests, with the level of enforcement of bans depending on the country in question. In addition, due to competing uses, there is limited land available for industrial plantations.
Smallholder timber agroforestry systems
Smallholders in developing countries have routinely cultivated timber trees for their own use alongside subsistence crops. In recent years, though, the cultivation of timber has been embraced as an important farm enterprise due to the mounting shortage of the commodity.The increasing recognition of the economic value of timber tree resources on farms, as well as policy-driven efforts to strengthen the sub-sector to attain social-economic objectives such as poverty reduction, has further contributed to the cultivation of timber by smallholders.
It is also now recognized that smallholders can have a competitive advantage in particular timber market segments. Furthermore, the demand for environmental services (e.g. carbon sequestration) from trees is expected to raise the potential market value of farmer-cultivated timber.Smallholder timber agroforestry systems fulfil a variety of objectives, with trees planted for subsistence use and for medium- and long-term sale. Timber trees also play a role in erosion control, soil fertility improvement and water catchment protection.
In Africa, indigenous timber species such as Cordia africana (East Africa cordia or Sudan Teak) Milicia excelsa (Iroko or African Teak), Newtonia buchananii (East African newtonia or forest newtonia) and Vitex keniensis (Meru Oak) are particularly recognized for these functions.Some timber species are good shade trees that can be used to enhance the productivity of understory crops. For instance, in some cocoa-growing regions, farmers have been able to establish plantations combining cocoa and timber production as a means of increasing cocoa production.approximately 700,000 hectares of exotic acacia plantations had been established in Vietnam, with half of this area being managed by smallholders, and the balance by forest companies and state enterprises.
Large commercial markets for wood produced by smallholders often depend on exotic trees, as illustrated by acacia and teak cultivation in Vietnam and Indonesia, respectively. By 2011, for example, approximately 700,000 hectares of exotic acacia plantations had been established in Vietnam, with half of this area being managed by smallholders, and the balance by forest companies and state enterprises.Indonesia is now the second largest producer of teak timber globally, with an industrial demand of more than 1.5 million cubic metres per year. A state-owned enterprise is the largest manager of plantations, but these satisfy less than a third of the demand, while an estimated 1.5 million smallholders on Java manage approximately 440,000 hectares of agroforestry systems where teak is the dominant tree crop.
Challenges facing smallholders
Studies by ICRAF have found that smallholders have the potential to influence their own timber value chains tremendously. However, a variety of challenges geared towards improving timber quality, and enhancing the management and pricing of timber markets, must first be resolved. These include
- market-related obstacles such as lack of the necessary marketing skills, and limited access to capital and market networks
- Inadequate knowledge and technical support for farmers in how to cultivate timber trees, and how to access good quality planting material
- Over dependence on a narrow range of trees, for example Grevillea robusta and Eucalyptus
- While diversification would enhance production options, most farmers do not have access to high quality germplasm.
Areas of future research and recommendations
- ICRAF research in the Peruvian Amazon has shown significant genetic variation that can be exploited to increase productivity in the locally important timbers, Guazuma crinita (bolaina blanca) and Calycophyllum spruceanum (capirona).
- More research is needed towards a more nuanced selection of species and provenances for particular locations, to produce better quality timber and achieve socio-economic benefits, and to retain farm biodiversity.
- In addition, research and development is needed to allow farmers to form associations, so that they have better access to technical information and to high quality planting material, as well as to support on marketing issues
- Policy developments are also necessary towards incorporating timber trees as components in payment models for smallholders for storing carbon.Download Full article (161 KB)
Conserving and sustainably using tree biodiversity
The biological diversity of trees (‘tree biodiversity’) is central to resilient and productive forests, agroforestry and other tree-based systems. The Tree Productivity and Diversity research theme (Trees theme) works on the conservation and sustainable use of this biodiversity. Resilience depends not only on the diversity of tree species but also on tree genetic diversity and varied habitats. Genetic diversity ensures resistance to diseases, adaptation to climate changes and other disturbances, and greater productivity. Species’ diversity and genetic diversity provide important products and ecosystem services. The genetic resources of thousands of tree species and other woody perennials are, however, threatened by fragmentation and overexploitation of forests, land conversion and climate change.
A particular concern in recent years is the foundational role of tree biodiversity in resilient forest landscape restoration, which can be threatened by the loss and inappropriate deployment of unsuitable species and genetic resources. Most restoration projects, including agroforestry initiatives, have not adequately considered the tree species and ‘provenances’ that they plant. Local, gendered knowledge about preferred tree species, their diversity and management, must be better harnessed to support sustainable restoration.
One reason why the effective use, and safeguarding, of tree genetic resources remains highly undervalued globally is that it is often difficult to visualise genetic diversity, at least initially, based on the time trees take to grow and mature and the very large number of tree species, making individual study only possible for selected species. In the limited number of cases where economic valuations of diversity have, however, been undertaken, the importance of this variation has become clear. Extending such work to a broader range of species and quantifying value more broadly than just in economic terms is, therefore, an important priority.
We consider below how the Trees theme engages in four interlinked aspects of work on tree biodiversity.
