Some people may have heard about shea butter as they have used it as a skin creme, or a hair conditioner. But it does so much more for people than that. It provides so many vital ecosystem services, I think of it as the "supermarket tree".
Page Contents
Background
Biology
The shea tree (Vitellaria paradoxa) is a small to medium-sized tree 10-15 m high. It is much branched, dense and spreading, so that its crown is round to hemispherical. The bark is thick and deeply fissured. The leaves grow in a spiral whirl from the tips of branches. Flowers grow in bunches of about 50, are creamish and can persist for 1 to 2 months. The fruits of the tree are oval, 5-8 cm long and 3-4 cm wide and are yellowish to green in colour. Under the skin, they have a pulpy layer surrounding a single seed.
Trees can live for up to 200 years. They start to produce fruit from about their 5th year on but do not crop reliably until they are at least 15 years old.
Distribution
BIOPHYSICAL LIMITS
- Altitude: 100-1200 m
- Mean annual temperature: 24-32 deg.C
- Mean annual rainfall: 600-1400 mm (with extended dry period)
- Soil type: Prefers dry and sandy clay soils with a good humus cover. Sub-optimal soils lower the crop yield.
Ecology
Shea trees play a major role in the ecosystems in which they are located. Given their longevity and hardiness, they often persist as one of the dominant trees in the ecosystem. Typically, 20 -25 trees grow in each hectare of savanna. They co-exist with cereal crops planted in their vicinity.
The flowers are self-fertile but pollination is greatly enhanced by bee activity and the flowers produce nectar to attract pollinators. A recent study indicates that the tree – able to produce nuts for 200 years – relies on pollinators that thrive when other tree and shrub species around it create a habitat to support the pollinators, especially bees.1
Surveys have revealed that many insects and other small animals make homes in the trees or use the trees to seek shelter from the elements. Certain insect larvae and parasitic plants actually prey on the trees. Fruit bats, birds and baboons are also involved in this food web.
Services
Carbon capture
The Global Shea Alliance (GSA) and Food and Agriculture Organization of the United Nations (FAO Regional Office for Africa), have released a study which underscores the shea tree’s potential to mitigate climate change in West Africa.
The study found that, at present, the shea value chain fixes 1.5 million tons of CO2 every year in West Africa. Relative to production volumes, every ton of shea kernel produced has a negative carbon footprint of 1.04 tons of CO2.
Prevention of desertification
Shea trees are prevalent across a region that is at risk from desertification. Because they have extremely deep root systems, they help to ameliorate wind erosion. Leaves and spoiled fruit that are not harvested or eaten by livestock add humus to the soil which aids water retention, as do seed husks left over from seed preparation.
Raw materials
Both soap and candles can be manufactured from the shea butter derived from shea nuts. The sap of shea trees has been used as an adhesive particularly to mend musical instruments. Also dyes may be produced from ashes from burnt wood. Wood from tree trunks is strong and termite resistant which makes it valuable for building structures. The wood is also burnt for charcoal for short term gain by some people.
Food
Nuts of the shea tree are regularly harvested for food production. A harvest of 5‐15 kg of shea nuts (kernels with shells) per year per tree is said to be average, but harvests up to 45 kg from trees that were protected and well‐tended have been recorded. Yields are not consistent from year to year.
The pulp of the fruit is eaten both raw and in products such as jams. The nuts inside the pulp are often eaten roasted.
Various parts of the shea tree are eaten by livestock such as sheep, goats, chickens and pigs.
Caterpillars of the Cirina moth which feed exclusively on the leaves of the shea tree, are dried and sold in markets in the region. They are rich in protein, and are a popular snack food.
Honey is derived from bees which are supplied with nectar from the shea tree flowers.
Shea butter is derived from the seed of shea tree nuts. It is prepared by an extraction process which can be primarily manual, involving mechanisation or by sophisticated chemical methods. Nuts harvested from the trees may be processed locally or maybe exported as dried kernels for processing elsewhere. If processed locally, the labour is traditionally supplied by the women of the nearby villages.
Fat derived from the seed of the shea tree is the main cooking oil for over 86 million human inhabitants. Globally it is used in baking along with/or replacing palm oil.
Health products
Shea tree products are used to treat a variety of ailments in countries in which it grows wild. These include :-
Stomach pain, headaches, eye problems, throat pain, treatment of wounds, rheumatism, diarrhoea, stomach problems, tooth health, lactation aid, and gynaecological problems. It has also been used for treating diseases in livestock. There are likely to be some pharmacognosy opportunities available.
On a global scale, shea butter is primarily used in the skin and hair care industries - soaps, moisturisers, shampoos, lipsticks, hair conditioners.
The shea butter global market size is not trivial. It exceeded USD 1.7 billion in 2020 and it is predicted to grow, subject to raw product availability.
Pest control
Infusions of the bark have selective antimicrobial properties, being effective against disease-causing Sarcina lutea and Staphyllococus aureus.
In addition, the wastewater from processing kernels is often used as a pesticide against weevils and termites.
Summary of services provided for us
- Carbon capture and storage
- Food products - for both people and livestock
- Prevention of desertification - by soil stabilisation and an increase in the water holding capacity of the soil
- Health and cosmetic products -both locally and increasingly in global markets
- Fuel
- Structural timber
- Pest control
- Raw material for lighting and dyes
- Services for ecosystem stability
Threats to the services?
Vitellaria paradoxa has most recently been assessed for The IUCN Red List of Threatened Species in 1998. Status VU- vulnerable
Climate change
Suitable habitats for Vitellaria paradoxa are likely to decrease by up to 13.25%, due to climate change effects.2
The shea tree is obviously a major food source for the Sahel region but population is doubling every 20 years. The growth rate of population (3% per year) exceeds the growth rate of food production (2% per year). This puts increasing pressure on crops. Shea tree are slow to get started and it is not easy to increase their numbers to ramp up production.
The uses of shea butter are being appreciated by a global audience, and this puts more pressure on tree harvesting.
While it is one of the richest regions in terms of natural resources and potential for solar energy, the Sahel faces serious challenges with high poverty, violent extremism and gender-based inequalities. ... The UN has declared that 80% of the pastoral land in the Sahel is degrading fast due to high temperatures, flood and droughts. This is causing migration and causing populations to move into areas where communities are already overstretched, and that is causing violence.3
The habitats are lost to ever-increasing agricultural shifts too, with a clear overall link to the impacts of human activity.
Across the African savanna belt from Senegal to Ethiopia, threats to shea trees (Vitellaria paradoxa) — the source of shea butter — have become a regional environmental concern. ...Poor farmers urgently in need of cash are cutting shea trees and reducing the fallow fields where shea regenerates.4
Shea is often targeted by charcoal traders who kill and sell the trees for instant cash which is far less than the long-term worth of their benefits.
What can we do to retain these services?
Implementation of integrated insect pest management strategies against shea tree pests
Shea fruit yields are likely to benefit from retention of a range of different tree and shrub species in the countryside. This will help to support pollinator populations.
Attempts are being made to determine the most reliable and quickest methods to propagate shea trees.
Outside help and funds to lessen some of the social problems that have direct bearing on shea trees e.g. new agricultural methods based on modern research
Dig deeper
- Lost crops of Africa
- Inventory of insects associated with sheatrees (Vitellaria paradoxa) (Sapotaceae) in central and northern Benin
- Globalization and the Shea Butter Industry
- New Study Highlights Shea’s Potential to Mitigate Effect of Climate Change
- Ghana's golden resource: How shea is empowering women and preserving savannas
- Local-scale tree and shrub diversity improves pollination services to shea trees in tropical West African parklands [↩]
- Climate change reduces the distribution area of the shea tree (Vitellaria paradoxa C.F. Gaertn.) in Burkina Faso [↩]
- The impact of climate change on conflict in Africa's Sahel region [↩]
- Shea trees are falling fast across Africa, victims of new pressures [↩]