m atlas of cassava m al

102 Pages·2016·23.81 MB·English

M ATLAS OF CASSAVA M AL
Historical, agroecologlcal and demographic aspects
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ISBN 958-9183-38-7
Historical, agroecological and demographic aspects
of crop distribution
S.E. Carter, L.O. Fresco and P.G. Jones,
with J.N. Fairbairn
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Centra Internacional de Agricultura Tropical
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Centro Internacional de Agricultura Tropical
Apartado Aéreo 6713
Cali, Colombia
CIAT Publication No. 206
ISBN 958-9183-38-7
Press run: 1000 copies
Printed in Colombia
June 1992
An Atlas of cassava in Africa: historical, agroecological and demographic aspects of crop distribution/S. E. Carter, L. O. Fresco and
P. G. Jones, with J. N. Fairbairn. — Cali, Colombia: Centro Internacional de Agricultura Tropical, 1992.
86 p., illus., maps.
Summaries in English, Portuguese and French.
1. Cassava — Plant distribution — Africa. 2. Cassava — Plant introduction — Africa. 3. Cassava — Soils — Africa.
4. Cassava — Climate — Africa. 5. Maps — Africa. 6. Cassava — Africa. 7. Cassava — Socioeconomic environment — Africa.
8. Africa — Population. I. Carter, Simon E. II. Fresco, Louise O. III. Jones, Peter G. IV. Fairbairn, James N. V. Centro Internacional de
Agricultura Tropical.
Drs. Simon Carter and Peter Jones are Senior Research Fellow and Head, respectively, of the Agroecological Studies Unit at CIAT,
Colombia. Dr. Louise Fresco is Lecturer in the Department of Tropical Crop Science of the Agricultural University, Wageningen,
Netherlands. Jamie Fairbairn is a Ph.D. student at the University of Reading, England.
CONTENTS
Page
Foreword and Acknowledgments v
Chapter
1 The Dynamics of Cassava in Africa 1
2 The Introduction and Diffusion of Cassava in Africa 9
3 Current Distribution of Cassava in Africa 15
4 The Relationship of Cassava Distribution to Environment and Population 19
5 Distribution and Change in Cassava Production in Three Countries 27
6 Conclusions 41
Summary 45
Resumo 49
Résumé 53
Bibliography 57
Appendix
I Sources of Data for the Map of Cassava Distribution in Africa 63
II Techniques and Methods Used for Environmental and Demographic Mapping
and Construction of the Cassava Distribution Model 67
III Population Data Used to Build the Model of Cassava Distribution 71
List of Acronyms Used in Text 79
Index 81

FOREWORD AND ACKNOWLEDGMENTS
The lack of adequate data on cassava production in Africa has for also encouraged us to develop a sound theoretical framework for
decades hampered development efforts. Scientists, concerned with the work presented here. Whilst still at CIAT, as economist in the
understanding cassava's role in agricultural systems and nutrition, Cassava Program, he collected most of the contemporary
and policy makers concerned with declining per capita food distribution data. Anne Warren also provided much valuable
production have had to contend with very limited information on a information. Jamie Fairbairn undertook the laborious task of
crop whose significance is increasing markedly. One of the collating all this distribution data to produce as consistent a
authors of the Atlas in particular has had first-hand experience of distribution map as possible, given the many limitations of the
the frustrations and challenges of conducting fieldwork in an data. Our thanks also go to Steve Romanoff who acquired
African country on a crop whose patterns of distribution and population data from the U.S. Census Bureau, and provided the
change are so little understood. original idea of an Atlas as an appropriate format to present some
of the work we had undertaken for COSCA.
The three authors of the Atlas were brought together by
planning meetings of the Collaborative Study of Cassava in Africa The Netherlands Institute of Advanced Science of the Royal
(COSCA), an interdisciplinary and interinstitutional effort to Academy of Sciences provided Louise Fresco an opportunity to
provide basic information on the crop in Africa, and to increase spend a six-month sabbatical at their facility in Wassenaar. The
the impact and relevance of research related to the crop. COSCA UTA and national programme staff involved in the COSCA
was undertaken by the International Institute for Tropical project and the members of the project's steering committee have
Agriculture (UTA), the Centro Internacional de Agricultura provided a sounding board for our ideas.
Tropical (CIAT), and national agricultural research institutions of
several African countries. While this study was still under way, The authors are grateful to J. Wigboldus, Department of
we felt it important to produce a document which illustrated Agrarian History of the Wageningen Agricultural University, for
current understanding of the distribution of the crop, as a reference his advice on various historical issues. Several graduates of the
for further research and data analysis. The COSCA project was Department of Tropical Crop Science, Wageningen Agricultural
wholly funded by the Rockefeller Foundation. As part of the University, have been involved in some way or other as research
project, CIAT received funds to develop a sampling frame for the assistants and during their M.Sc. thesis work. The contributions of
first phase, and to assist in the design, personnel training and S. Chin a Tarn on Nigeria, B. Meertens and S. Duiker on
initial data analysis for this phase. This Atlas is an additional Tanzania, L. Kater on Zaire, H. Langeveld on country studies in
output from CIAT's portion of the project funds. general, and J. Stoorvogel have been most valuable. We also wish
to thank CIAT's library staff for assistance with computerised
The Foundation also provided a personal grant to Louise cassava abstracts, especially Nora Rizo.
Fresco for a desk study on cassava. The authors are very grateful
to the Rockefeller Foundation, especially to Dr. Robert Herdt, for Mauricio Rincón, of CIAT's Agroecological Studies Unit,
supporting the production of the Atlas. laboured long and hard over the production of the colour maps, to
develop them from their original computer format to that presented
The attempt to construct an Atlas of Cassava in Africa has here, via the laborious process of preparing them for printing. We
been encouraged by many individuals and events. But if we are to are grateful to the Royal Tropical Institute, Amsterdam, S.A.
single out one person whose work has provided us with special Agboola and Oxford University Press for permission to reproduce
inspiration, it must be Professor William O. Jones, emeritus Figures 8,9 and 12, respectively. Ligia Garcia prepared the keys
professor of the Stanford Food Research Institute. His seminal to the colour maps and most of the black and white illustrations.
work, Manioc in Africa, published in 1959, remains unsurpassed P. Versteeg drew some of the country maps; and Martha Gomez
as a source of knowledge on the crop, at least until the COSCA typed most of the manuscript. Finally, we would like to thank
study is complete. One of us had the opportunity to travel to James Cock, Mabrouk El-Sharkawy, Clair Hershey and Marcio
Stanford in the spring of 1989, to discuss various aspects of the Porto for reading the manuscript and providing much helpful
theoretical framework and consult the SFRI's library. comment and criticism, and Elizabeth McAdam de Pâez for her
speedy and efficient editing of the final manuscript.
The contributions of many other individuals have been most Responsibility for errors and omissions, needless to say, lies
valuable, and we would like to thank the following especially: entirely with us.
John Lynam, of the Rockefeller Foundation in Nairobi, who not
only took a major initiative in formulating the COSCA study, but

CHAPTER 1
THE DYNAMICS OF CASSAVA IN AFRICA
Scope and Objectives of the Atlas Theoretical Framework: The Dynamics of Cassava in
Africa
Since its introduction into the African continent in the course of
the 16th century, cassava has gradually become one of the The concept of 'niches' for cassava
dominant starchy staples, particularly in the humid lowlands where
it may provide over 50% of the local diet. The successful The question of cassava's relevance to the African food
integration of cassava in African cropping and dietary patterns crisis, and, more broadly, to African development, forms the
takes on special importance as Africa is the only region where per background to the theoretical framework. This section attempts to
capita food production has apparently been declining in the last develop a series of hypotheses that will allow analysis of the
two decades. During that period, overall cassava production in distribution of cassava in Africa as a function of agroecological
Africa has nearly doubled, even if, according to official statistics, and socio-economic parameters and so provide the basis for a
this has not allowed it to keep pace with population increase (De model that explains the spatial distribution of cassava.
Bruijn and Fresco, 1989 ). At the same time, there are various,
Two ideas are central in this approach. Firstly, that the
often unchecked and contradictory, indications of rapidly changing
distribution of a crop is not just a matter of chance or coincidence,
patterns of agricultural production, accompanied by shifts in the
but reflects a combination of factors that explain the logic behind
relative importance of food crops, particularly of cassava.
the crop's role. Secondly, that cassava, because of its versatility
Since the seminal work of W. O. Jones, Manioc in Africa, and special characteristics, occupies very different niches or roles
which appeared in 1959, no comprehensive overview of cassava in in African farming systems. These roles seem to vary according to
Africa has been published. Our understanding of long-term the dynamics of the farming system, in particular, to the degree of
changes in the relative importance of cassava in different intensification and pressure on resources, especially land. In other
agroecological regions is extremely limited and often based on words, for a given agroecological zone, the presence of cassava
arbitrary speculation rather than on fact. Aggregated food crop and the manner in which it is grown may be an extremely useful
statistics in Africa are noted for their poor quality, and cassava's indicator to characterise changes in African agriculture. This
special nature as a food reserve crop is likely to increase statistical means that we should inevitably take a long-term view, not only to
inaccuracy. Although numerous studies by social scientists may correct information for seasonal and interannual variations, but,
contain important information on the crop, little effort has been more importantly, to allow an investigation of the role of cassava
undertaken so far to view these in a comparative and historical under changing agroecological, demographic and socio-economic
context. Even fewer attempts have been made to relate their conditions.
findings to crop science research which, in turn, has rarely been
linked to the changing role of cassava in sub-Saharan Africa. What makes cassava so special and different from African
staples, such as maize and sorghum, and even other moisture-rich
This Atlas of Cassava in Africa aims to provide a review of starchy staples such as yam and plantain? Its most important
the geographic distribution and importance of the crop based on
feature is the width of its ecological amplitude, that is, its
existing statistical data on climate, soils, population and
adaptability to a wide variety of ecological and agronomic
production, combined with selected case studies. It goes without
conditions. In contrast to other staples, it grows well under
saying that this effort is severely limited by the paucity and poor
marginal, as well favourable, conditions of soil fertility and
quality of the available information. Nevertheless, the Atlas is the
rainfall. It has no critical growth stage after establishment, during
first attempt to present a comprehensive framework for the
which a short stress period might decrease yield (for details of
interpretation of agroecological and socio-economic data on
cassava's requirements see Chapter 4). The implication is not only
cassava and to describe the crop's spatial patterns for Africa. Not
that the crop is found in a wide range of environments across the
only do we hope that it will encourage other researchers to add to
continent, but also that within the same agroecological zone, it can
this framework, we also feel that the Atlas will help focus research
adapt to microvariations in relief, soils and cropping systems.
on cassava and cassava-based cropping systems more accurately.
Apart from this ecological versatility, cassava also displays certain
characteristics that make it adaptable to a variety of
After a brief introduction to the theoretical issues involved in
socio-economic conditions. Its tolerance of low field labour inputs
the study of the dynamics of cassava in Africa, the Atlas starts
and variability in planting and harvesting dates make it much less
with a chapter on the introduction of the crop on the continent.
tightly constrained by seasonality than other staples, while it
This is followed by a description of the current distribution of the
remains a high producer of dry matter (and protein, if aerial parts
crop. The next chapter describes and maps the agroecological
are included) per unit of land and labour. Although fresh cassava
environment in the light of cassava's requirements. Patterns of
starts to deteriorate within 24 hours and processing is rather labour
human population are described, and related to the distribution of
intensive, its products can be relatively easily stored and
the crop by using a spatial regression model and taking into
transported. Finally, its economically valuable parts are not
account identified environmental differences. Subsequently, three
required for reproduction (de Vries, 1978; Fresco, 1986; Jones,
country studies, on Nigeria, Tanzania and Zaire, allow a
1959). These features not only explain the successful introduction
discussion of the integration of agroecological, socio-economic
of cassava in Africa (see Chapter 2), but allow us also to
and, to a lesser extent, recent historical data as a means of
understand how the crop fits into a great variety of African
validating the model and the theoretical framework on which it is
farming systems, i.e., why it occupies certain 'niches', and to
based. The final chapter reviews the main findings in the light of
gauge its overall importance in Africa.
the theoretical framework on agricultural dynamics in Africa and
draws conclusions with respect to the validity and significance of
African agricultural systems are highly variable. Variations in
the results.
crop species and varieties and cultural practices occur over short
distances. The interaction of a wide range of agroecological and
socio-economic factors has resulted in a variety of conditions
1. For this and further citations, see Bibliography, p. 57-61.
under which cassava is grown, processed, marketed and mainly occurring in semi-arid zones. Mixed
consumed. Moreover, these conditions are not static, but are crop-livestock systems are found in the semi-arid regions
subject to constant change, for example, as a result of population of Africa, particularly in the west and south. If livestock
growth and urbanisation. The key issues which this Atlas tries to is used for land preparation, this can lead to higher yields
address are What factors determine the relative importance of (timely planting, better seedbed preparation), but it has
cassava, as expressed by the area planted to the crop? and What been concluded that, in Africa, animal traction per se
future scenarios of cassava production in Africa can be envisaged? generally affects output through increases in land brought
In order to do this, we must take a continent-wide view of the under cultivation rather than through yield increases
crop, as well as try to take into account the diversity of (Pingali et al., 1987).
socio-economic and agroecological niches in which it is grown.
The niches of cassava in each of these farming systems are
described briefly below:
Land use and cassava in Africa
Shifting and/or fallow cultivation. Since its introduction, the
African agriculture has been subject to considerable change,
'classical' niche of cassava has been as a last crop before fallow,
at a more rapid pace, and over longer periods than one would be
i.e., following a soil fertility demanding staple (e.g., upland rice)
led to believe from some 'snapshot' studies of 'traditional'
or cash crop (e.g., cotton, tobacco). The crop was left to merge
farming. Intense agricultural transformation has characterised
with the surrounding bush or forest vegetation, and harvested
many parts of Africa over the last few centuries. Within the
according to need. As long-fallow, shifting cultivation is being
constraints of climate and soils, the two major, interrelated
(although gradually) replaced by short-fallow cultivation in nearly
elements contributing to agricultural change are population growth
all areas of Africa, soil fertility is not adequately restored and
and incorporation into the global political economy (Hayami and
cassava moves forward in the crop sequence and/or becomes the
Ruttan, 1971; Ruthenberg, 1980). As a result of incorporation,
dominant intercrop. On many savanna fields of the Bandundu
infrastructural and technical change have taken place, bringing
region of Zaire, for example, cassava is now the first crop after
strong external pressures to bear upon agriculture, through
fallow, grown immediately after clearing. There is ample
government price controls, fiscal demands, the vagaries of
evidence, from such distinct places as Mozambique, Cameroon,
international markets and, last but not least, the encouragement of
Tanzania, Zaire, Central African Republic, that cassava becomes
cash crop production, promoting, in turn, the production of
the dominant intercrop (Fresco, 1986; Guyer, 1984; B. Meertens,
low-cost food crops. The introduction of cassava, maize and
1990, personal communication; Newbury and
groundnuts, now major African staples, was an essential feature of
Ebutumwa-Bw'emiogo, 1984; Rosling, 1987; see also Chapter 5).
the process of incorporation and had a profound effect on African
Although cassava is considered a woman's crop in many regions,
agriculture well before the demographic changes occurring after
it appears to be grown also by single men, widowers or men
World War II.
whose wives are ill. In other words, cassava's comparative
advantage in short-fallow shifting cultivation is as a low external
Ruthenberg (1980) has analysed in detail the types of farming
input crop that still produces an acceptable yield on unfertilised
and cropping systems that occur in various agroecological zones,
fields with low labour inputs.
as well as their evolutionary tendencies. Although hunting and
gathering have remained important throughout man's history in
Permanent cultivation. In permanent systems with
Africa, there seems little doubt that shifting cultivation developed
perennials, cassava is usually not a major feature of the system. It
as the predominant form of land use, once people began to
is intercropped temporarily while the perennial crop is being
domesticate crops (possible exceptions may be the arid and
established, or it may be found on extensively cultivated fields that
semi-arid areas). Depending on the agroecological zone, patterns
are destined as food reserves and are irregularly harvested.
of land use diverge from shifting cultivation to permanent or
Occasionally, it is included in permanent gardens situated near or
mixed systems, largely in response to population growth. African
on the compound (Lagemann, 1977). Continuous cultivation of
farming systems demonstrate three basic forms of land use:
cassava (i.e., without fallow) takes place exceptionally in
commercial plantations (Nigeria, Congo). In areas with wet rice
1. Shifting or, when fallows shorten, fallow cultivation, with
cultivation in West Africa, cassava may be grown on residual
land use closely mimicking natural climax vegetation
moisture during the dry season, provided soils are not waterlogged.
through the limited removal of trees and the restoration of
natural vegetation during fallow. These systems have
In areas of relatively high soil fertility and high population
probably been widespread throughout Africa, but are now
densities, permanent cropping may have evolved even in
mainly found in the humid and subhumid lowland zones.
precolonial times (Gleave and White, 1969). Subsequent
Labour productivity is high as long as fallows are
introduction of perennial cash or plantation crops, such as coffee
sufficiently long to restore fertility (Greenland and
and cocoa, created a need for an 'easy' staple with few demands
Okigbo, 1983). Reduced fertility, as well as weed
on labour, high productivity per unit of land area, and which could
infestation, are reasons for abandonment of land.
be grown between the young trees as the plantation was
established. Under these conditions, cassava today still holds a
2. Permanent perennial and/or annual cultivation. In humid
comparative advantage over other staples.
zones, shifting cultivation will be replaced gradually by
systems with perennial crops or wet rice cultivation,
while permanent cultivation of non-irrigated crops or Pastoral and mixed systems. Even where the livestock
regulated leys are only found in semi-arid regions. component is fully integrated in crop production, the animals are
Permanent cultivation in Africa is found in traditionally left to forage for themselves. During the rainy season, the animals
densely populated areas, either because of confined space must therefore be kept away from the fields. Cassava seems to
(islands, steep hillsides) or in fertile highland areas where, present problems in mixed systems because it is often the only
for ecological reasons, population has been concentrated crop that provides foliage during the dry season. The difficulty in
(e.g., Kikuyuland, the Great Lakes in Central Africa and protecting it from livestock explains why it is rarely found under
the Jos Plateau). these systems. It may occur on residual moisture during the dry
season near river beds that are sufficiently removed from the
3. Pastoral or mixed crop-livestock systems, with varying village or can be fenced in or watched. However, as soil fertility
degrees of integration between crops and livestock, constrains the traditional cereal crops, cassava may be increasing