| Summary: | The harvesting and commercialization of non-timber forest products (NTFPs) both present
social, economic and environmental challenges. Thousands of NTFPs are harvested from
wild populations around the world and the use thereof meets the subsistence and
commercial needs of many millions of people. Yet few such products are being sustainably
harvested, presenting a threat to the survival of many species. As commercial interest in
NTFPs grow, it is increasingly important to understand the biology of the species being
harvested. A number of species have oil-bearing seeds which provide ingredients for
cosmetic formulations. Baobab ((Adansonia digitata L.) seed oil, is one such ingredient,
which has rapidly become popular on global markets.
Baobabs are an iconic, very long-lived, African savanna tree species known
throughout their range as a source of food, fibre and medicine, yet global demand for its fruit
derivatives (both seed oil and fruit pulp) have raised concerns about sustainability. This
study undertook to investigate the ecological aspects of fruit harvesting and to document the
socio-economic benefits of commercializing the fruit.
Research was conducted in northern Venda, Limpopo Province, South Africa.
Population dynamics, fruit production, phenology and recruitment were investigated in five
land-use types, namely: nature reserves, rocky outcrops and plains, representing natural
land-use types, and fields and villages representing human-modified land-use types.
Density of trees was determined from transects, fruit and flower counts were done on 106
trees over 2-3 seasons, seed viability and seedling/sapling survival rates were determined
and interviews with harvesters were conducted in villages across the study area. Data
analysis used standard univariate statistical methods and the results were used to create a
stage structured population projection matrix model.
Villages and fields had higher densities of trees (2.16±0.44 and 1.13±0.52 plants/ha)
than plains and rocky outcrops (0.96±0.25 and 0.83±0.24 plants/ha). All land-use types had
positively skewed size-class distribution (SCD) curves and negative to flat SCD slopes
indicating low recruitment. Quotients and the permutation index suggest that recruitment
and mortality are episodic events, but nonetheless that the population has been stable.
Mature fruit production was higher in villages and fields (89.59±34.61; 88.26±32.20fruit/tree)
than nature reserves, plains and rocky-outcrops (1.90±1.15; 28.64±12.56; 12.56±5.59
fruit/tree). Predation on immature fruit by baboons resulted in 58-85% loss. Inter-annual
variation in fruit production was significant, with a 2½-fold difference between the highest
and lowest years. Flowering followed a steady-state pattern, lasting 1-5 months and peaking
in November. Mean flower numbers/tree (711±72 and 287±33) varied significantly between
sequential years, but not fruit-set (average of 20±4%). Baobab seed exhibited high viability
(>91%) and formed persistent seed banks. Seed production was substantial (5500±2334 seed/ha); thus recruitment does not appear to be seed-limited except in areas where
baboons are found. Seedling emergence was staggered over two growing seasons. In plots
where livestock were excluded (closed plots) 6.33% of seed emerged with a mean natural
germination rate of 328±28 days and of these 94.44% died of moisture stress and insect
browsing within 21±5 days. In open plots only 2% of the seeds emerged with a germination
rate of 377±5 days and all of them died from livestock browsing within 12±5 days. Planted
sapling survival in closed plots (65%) was significantly better than in open plots (10%) where
repeated livestock browsing and trampling was responsible for high mortality rates. Matrix
model output indicated that high livestock numbers and baboon predation of fruit cause
population decline. Under zero to moderate livestock numbers, populations in communal
land-use types are able to tolerate fruit harvest rates of between 33-90%.
Harvesters were marginalized people to whom the sale of baobab fruit had an
income value 4 times higher than its subsistence value. The sale of baobab fruit contributed
38% to the overall cash income received from NTFP sales, helping to alleviate poverty and
increase access to a cash economy.
It was concluded that the management of baobab populations require an integrated
approach incorporating human needs and environmental variables. The long-lived nature of
baobab trees provides a buffer against short-term pressures (an excellent example of the
‘storage effect’), but unabated environmental degradation and climate change threaten
populations. It is recommended that government agencies, businesses, traditional
authorities and harvesters invest in strategies that will protect baobabs and boost
recruitment to safeguard future populations and ensure multi-generational benefits for rural
people.
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