Download - Innocent Bakam and Christopher Legg
Innocent Bakam and Christopher Legg
System Dynamics for Landscape Modelling in Cameroon
Outline
• Modelling objectives
• Lessons learnt
• Difficulties
• Future developments
Modelling objectives
• improve understanding of the delicate balance between humans and their environment
• assist in formulating policies for future development
HOUSEHOLDLAND
PATCH
INFORMATION
LABOUR
YIELDS
MULTIPLE
PATCHES
MULTIPLE
HOUSEHOLDS
VILLAGE LAND
TENURESYSTEM 1
SYSTEM 2
GISGLOBAL
POPULATION
DECISIONS
INTERACTION
GLOBAL
DEVELOPMENT OF THE MODEL USING SIMILE PLATFORM
Where are we now?
• Fieldwork and other data collection complete
• Simile Models for Awae and Akok operational but not yet calibrated or validated
• Simile model for Nkometou almost complete
Main lessons learnt
1) Extreme complexity of cropping systems in African humid forests, evolved to ensure food security and minimise labour demands
2) Labour availability is critical to all farming activities and household decisions
3) Population pressures force gradual abandonment of traditional farming systems at densities greater than about 20 persons per square kilometre
4) Understanding land use and tenure patterns requires careful planning and development of sampling techniques
A dominant dynamic is the conversion of forest and fallow to cultivation in a twice-yearly cycle of
slash-and-burn
Logged and Secondary Forest
Melon/Plantain System
Cocoa System
Mixed Food System
Fallow
6-9 years
Wetland Maize
Oil Palm
Land use dynamics in the humid forest zone of
Cameroon
Main lessons learnt (2)
1) Agricultural intensification, with shorter fallows, smaller fields, and increasing emphasis on mono-culture cash-crops can support population densities in excess of 100 persons per square kilometre, but only at the cost of soil degradation or high levels of inputs
2) Forest bio-diversity is rarely maintained at population densities above 20/km2
3) In areas where forest is still abundant, most clearing of forest is for nutritionally unproductive essep (forest melon) fields, not for mixed-food fields
0
10
20
30
40
50
60
70
80
90
Akok Awae Nkometou
village
Area/HH
pop/km2
Village Area HouseholdsArea/HH HH/km2 pop/km2Akok 9480 124 76.5 1.3 7.8Awae 820 49 16.7 6.0 35.9Nkometou 1463 208 7.0 14.2 85.3
Available land per household decreases from 75 hectares in Awae to 7 hectares in Nkometou
Population density increases from 8 persons per square kilometre to
85
Average size of mixed-food fields declines from 0.24 hectares in Akok to 0.10 hectares in Nkometou
Average size of cocoa fields declines from 1.32 hectares to 0.66 hectares
Field Sizes
0
0.2
0.4
0.6
0.8
1
1.2
1.4
Akok Awae Nkometou
Hec
tare
s
Asane
Cocoa
Essep
Mixed food 1
Mixed food 2
Maize
Tomato
Potato
Other Veg
Asane and essep are no longer cultivated in Nkometou because of land shortage and lack of forest.
A range of market-orientated monocultures have become important instead
0%
20%
40%
60%
80%
100%
Nkometou Awae Akok
villages
per
cen
tag
e cu
ltiv
atio
n
forest melons
monocultures
mixed food
cocoa
Nkometou Awae Akok
cocoa 26.2 41.2 41.8
mixed food 38.2 41.6 48.7
monocultures 35.6 8.4 2.2
forest melons 0.0 8.8 7.3
Proportion of cultivated land under mixed food crops
declines from 49% in Akok to 38% in Nkometou
Proportion under monocultures such as maize and tomatoes increases from 2% in Akok to
36% in Nkometou
Forest melon/plantain fields decline from 7-9% in Akok
and Awae to zero in Nkometou
Relative importance of cocoa declines as more fallow is
cultivated as monocultures
Difficulties• Lack of data and agronomic expertise in
modelling team to calibrate and validate the model
• Lack of time to achieve the numerous challenges raised by the modelling activity (lead scientist only part-time in modelling programme for past two years)
• Problems with the Simile platform which is still under development
Future developments (dependent on funding)
• Calibration, to ensure that outputs are in reasonable ranges
• Validation of all sub models within a multi-disciplinary team (agronomist, pedologist, sociologist, economist, modeler), to ensure that the model is scientifically valid
• Development of more friendly user interfaces to ease the adoption of the model by end-users
The Model has become extremely complex
Future developments (2)
• Validation in the field with stakeholders (farmers, NGO, policy makers) to ensure that the model reflects the different points of view
• Testing of different scenarios and development of appropriate development strategies
• Extrapolation of outcomes to Benchmark and eco-zone
• Dissemination of model results through publications, role games and seminars