Download The role of Agroforestry in mitigating climate change in southern Africa

Utilizing tree crops to mitigate greenhouse gas emissions: the case of
southern Africa with chronic food insecurity
S.A. MNG’OMBA, F.K. AKINNIFESI, S. CHAKEREDZA, G. SILESHI, O.C.
AJAYI and BI NYOKA
World Agroforestry Centre (ICRAF), P.O. Box 30798, Lilongwe 3, Malawi
Email: [email protected]
Global contribution of agriculture to greenhouse gas (GHG) emission has been
estimated to be around 20% for carbon dioxide, 50% for methane and 70% for nitrous
oxide. The GHG are emitted from domestic livestock (methane and nitrous oxide),
rice cultivation (methane), burning (methane, carbon monoxide, nitrous oxide, and
oxides of nitrogen) and agricultural soils (methane, carbon dioxide and nitrous oxide).
Smallholder farmers of southern Africa rely on agriculture for their livelihoods, but
food production is often inadequate. The use of fossil fuels contributes huge amounts
of GHG into atmosphere, but mitigation of GHG emissions due to agriculture is
comparatively cost-effective. Fossil fuel substitution by bio-fuels has been recognised
as viable mitigation. For southern Africa with chronic food insecurity, bio-fuel
research emphasis should be on alternative tree crops adapted to marginal lands rather
than field crops such as maize. Planting trees, fruit and fodder trees could improve
food security and creates a carbon sink. The use of rapid digestible animal feeds
reduces the passage time of food in the digestive system and hence reduces methane
production. Perennial tree crops enable to achieve carbon credits. In this paper we
present the knowledge and research challenges on the use of tree crops to reduce
GHG emissions with southern Africa as a main focus.
Key words: Agriculture, greenhouse gas, crop yield, livelihoods
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Introduction
Agriculture dominates the main activities of many countries of southern Africa. This
is an indication that livelihoods of many people of southern Africa depend on
agriculture. For instance, Malawi’s economy depends on agriculture, a main source of
foreign income. However, there is low crop production and this has crippled the
livelihoods of many people. There are also many reasons for the poor crop
production. Unfavourable change in climatic condition has been one major cause of
crop failure. Such unfavourable climatic changes to agriculture would remain a major
concern despite availability of farm inputs. At national level or let alone at farmer
level, it would be difficult to contain the changes in climate. This would require
collective efforts.
In the wake of unfavourable climate changes, crop production has been
threatened and this adversely affects the livelihoods of many people in the poor
countries. Central to this climate change is the emissions of greenhouse gases (GHG)
into atmosphere. The GHG includes carbon dioxide, methane, carbon monoxide,
nitrous oxide and oxides of nitrogen. A balanced level of these GHGs in atmosphere
is beneficial to human beings. However, a high accumulation of GHGs in atmosphere
would result in unfavourable weather conditions such as a rise in high temperature,
floods and drought among many others. This would adversely affect food production,
especially in countries with fragile economy.
Comparatively, the use of fossil fuels contributes huge amounts of GHG
emissions into atmosphere, but mitigation of GHG emissions due to agriculture is
cost-effective compared to emissions from fossil fuels. Generally, plants have been
recognised as fossil fuel substitution (bio-fuels) and sinks of GHG. In southern Africa
and other countries or regions, trees (such as Jatropha curcas) and field crops are
being exploited as sources of bio-fuels. This has been taken as a way of climate
change mitigation. However, southern Africa has to make a judicious selection of
climate change mitigation measures that would not impinge on food availability. This
is because food production has already been low and there are also seasonal food
shortages in the region. Land holding size, especially arable land for agriculture has
been a limiting factor to crop production. It is envisage that climate change will
impose an enormous constraint to crop production and adversely affect the economic
growth of southern Africa. While it is clear that issues of climate change need urgent
attention, mitigation measures must be tackled with food security consideration.
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Greenhouse gas emissions
The contribution of agriculture to greenhouse gas (GHG) emissions has been
estimated to be low (20% for carbon dioxide, 50% for methane and 70% for nitrous
oxide) compared to emissions from fossil fuels. Carbon dioxide has been a major
player in climate change. Major sources of GHGs from agriculture are domestic
livestock (methane and nitrous oxide), rice cultivation (methane), burning (methane,
carbon monoxide, nitrous oxide, and oxides of nitrogen) and agricultural soils
(methane, carbon dioxide and nitrous oxide). Carbon dioxide has been single out as a
highest greenhouse gas being emitted to atmosphere from agriculture.
Incidences of climate change
Greenhouse gas emission into the atmosphere will result in droughts and rise in
temperatures. These are examples of catastrophes that human beings in southern
Africa have already experienced. For instance, in Malawi, El Nino and La Nina global
phenomena already caused floods and droughts. There were severe droughts in
1991/92 and 1994/95 growing seasons and floods in 1999/2000 and 2000/2001 rainy
seasons. Landslides occurred in 1992/93 rainy season due to prolonged torrential rains
in southern parts of Malawi. They caused loss of lives and damage to socio-economic
structures in Phalombe district. These are some catastrophic examples of climate
change. This indicates that if greenhouse gas emission is left unabated, it will cause
numerous catastrophes to the lives of people.
Mitigation
The reduction of emissions of GHGs into atmosphere and enhancement of carbon
sinks provide both opportunities and challenges for the socio-economic development
of any country. Therefore, each country must take a key role towards reduction of
GHGs into atmosphere irrespective of its socio-economic status and contribution to
GHG emissions. It is envisaged that climate change will have an adverse effect on
countries with fragile or poor economy. There is a need to exploit available
opportunities by using appropriate technologies in order to effective mitigate GHG
emissions. According to the United Nations Framework Convention on Climate
Change (UNFCCC), the ultimate objective is to ‘stabilize concentration of greenhouse
gas in the atmosphere in such a way that the level would not be dangerous to cause
anthropogenic interference with the climate system’.
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Bio-fuels
Production of potential tree crops for bio-diesel has been promoted in some countries
of southern Africa by both private and non-governmental organisations, and other
development agencies. J. curcas has been one such tree promoted in southern Africa
and many other countries for bio-fuel production. However, there is little information
or research on its viability or cost-benefit for farm production although it might have
ecological advantages. It is believed that J. curcas is less expensive to produce than
other energy crops such as rapeseed and soybeans (Tomomatsu and Swallow, 2007).
It is believed that plantation of J. curcas is expected to reduce poverty and improve
the livelihoods of people in the rural communities as a source of income
(http://www.unctad.org). However, local communities might not achieve the desired
rural economic benefits and this could be due to competition with larger plantations
unless they operate as farmer groups and are able to operate oil extraction by
themselves (Tomomatsu and Swallow, 2007). In view of this, it would important to
assess the benefits that smallholder farmers will achieve by investing in J. curcus
plantation compared to other alternatives. At the same time, it is important to consider
issues of food security.
Cost-benefits
Cultivation of J. curcas must be based on the cost-benefit since there are no
convincing studies to indicate its profitability. Furthermore, there are no data to
compare its profitability to petroleum products, food or other cash crops. It is
anticipated that smallholder farmers could realize profits if they will be involved in
both primary (oil extraction) and secondary processing (transesterification). Data in
Table 1 indicate that investing in mango production is more profitable than J. curcas
production. The revenues derived from irrigated J. curcas compare well with mango
produced under rainfed condition. This suggests that smallholder farmers are better
off by investing in some fruit tree production. However, cashew nut and coconut
production had lower revenue per unit land. Obviously, if smallholder farmers are to
extract the oil and do transesterification on the farm the revenues per unit land would
be high, but the intricacies in these technologies might not be in their favour.
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TABLE 1 Cost -benefit analysis adapted from Tomomatsu and Swallow (2007)
Crop
Revenue per acre (US$)*
Jatropha (rainfed)
150 -180
Jatropha (irrigated)
320-384
Mango
347
Cashew
145
Coconuts
55
* Production costs are not included in all calculations
In view, that there are still so many gaps on cost-benefits of J. curcas, it is
perhaps important to confine its cultivation to marginal lands. The advantages lie in
the fact that it is drought tolerant and there are indications that J. curcas can be grown
on marginal lands.
Intercropping
If J. curcas trees are to be grown on smallholder farmers’ arable land, there must be
studies to investigate different intercropping systems in order to maximise land
productivity. This is due to limitation of land holding sizes per household and food
security problem facing many countries of southern Africa. For instance, the growing
fruit trees (mango, cashew nut etc.) or other field crops with J. curcas. There is also a
need to select superior germplasm since there is a wide range of genetic variation
within J. curcas tree provenances for southern Africa. Apart from profitability
comparisons of growing J. curcas to other crops such as fruit trees, potato, cassava
and many others, other environmental benefits must also be taken into account
(Tomomatsu and Swallow, 2007). In southern Africa, it might be ideal to promote
Jatropha plantation on estate farms, but not on smallholder farmers’ arable land.
Food crops
Many countries of southern Africa are experiencing food shortage and chronic
malnutrition. This is largely due to erratic rainfall attributed to an impact of climate
change, and also due to inadequate farm inputs. The increase in human population is
exerting an enormous pressure on arable land per household and this does not give
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small holder farmers a chance to fallow the land. This has contributed to soil
infertility. Consequently, crop failure such maize, a staple food for many people, has
been rampart in southern Africa. The use of food crops such as maize, legumes and
sugarcane to produce bio-fuels will definitely worsen food insecurity problem. Some
legumes, maize and sugarcane have been processed into ethanol, but this would
impinge on food security of many people of southern Africa. Therefore, technologies
that spare the use of food crops in climate change mitigation would ensure food
security. This is because a shift by smallholder farmers from food crop production to
Jatropha is likely to bring increase in food prices as a result of reduction in food
supply.
Utilization of marginal lands
The use of bio-fuels has been recognised as a measure to reduce huge amounts of
GHG emitted to atmosphere due to the use of fossil fuels. As southern Africa is
exploiting trees as potential sources of bio-fuels, it is important to consider issues of
food security in the wake of limitation in arable land availability. The use of arable
land for production of tree crops such as J. curcas for bio-fuels would reduce the
cultivable land for food crops. Therefore, the use of marginal lands would be suitable
for the production of such potential bio-fuel trees to avoid competition.
Fodder for livestock
The use of rapid digestible fodder crops will reduce methane production since this
limits enteric fermentation in the alimentary canal of an animal (Moeletsi, 2007).
However, this has to consider its impact on ruminants as they regurgitate to obtain
more nutrients. More research is needed to exploit this avenue except for ruminant
animals. The use of fodder trees/shrubs would support livestock industry and hence
provide the needed proteins to the humans.
Fruit trees
Generally, fruit trees are replaced or cut down after several years. Therefore, fruit
trees could provide a carbon sink, and hence a good mitigation measure. In some
instances, fruit trees are left to grow for twenty years or more with little or no major
reduction in fruit yield. The data in Table 1 show that some fruit trees could be
profitable and also important sources of food to many people. The growing of fruit
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trees could ensure food security and income generation to many households in the
southern Africa. It would be advisable for small holder farmers to invest in fruit trees
so as to achieve food security and income generation.
Wetlands
Wetlands are important natural resources although they are sources of natural
methane. Wetlands are ecosystems which support lives of many plants and animals.
They also act as natural water purification system, and hence they provide the much
needed biological, ecological and socio-economic benefits to human beings. With
respect to methane production due to wetlands which could also be good areas for rice
cultivation, it is important that management of wetlands must be done in a way that it
minimises GHG emissions.
Conclusions
Countries in southern Africa need judicious technologies or measures that would
mitigate GHG emissions without impinging on food production. Mitigation measures
that exploit trees as alternative sources of bio-fuels must be supported as long as they
do not compromise on food security. It could be advisable for small holder farmers to
commit the marginal land to Bio-fuel tree production and food crops to arable land.
Non-food crops such as J. curcas should be used for bio-fuels, but not food crops.
More research work is needed to establish profitability of growing Jatropha and the
impact of any proposed mitigation technologies on food production.
References
Caelho ST,. 2005. Biofuels: Advantages and Trade Barriers. United Nations
Conference on Trade and Development. Available at:
http://www.unctad.org/en/docs/ditcted20051_en.pdf. Access 10 July 2008.
Moeletsi ME., 2007. Agricultural contributions to, and mitigation of, greenhouse gas
emissions. Proceedings of soil science society of South Africa, South African Society
of Crop Production and Southern African Society for Horticultural Sciences
Combined Congress. 22-25 January, Badplaas.
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Tomomatsu Y and Swallow B. 2007. Jatropha curcus biodiesel production in Kenya.
Economics and potential value chain development for smallholder farmers. WP 54.
Nairobi. World Agroforestry Centre, 33 pg.
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