Vulnerability of Rice and Maize Yields to climate variability in the Sudano Sahelian Zone of The Gambia: Drivers and Adaptation Options
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Date
2021-07-12
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Abstract
Staple food crops are considered as the driving force for household food security and
source of livelihood activities for many developing nations. Farming practices face many
challenges due to the adverse impacts of climate change and variability in the 21st
century. This study assessed the extent to which maize (Zea mays L.) and rice (Oryza
sativa L.) yields are vulnerable to climate variability in the Lower River Region of The
Gambia. The influence of climate variability was assessed using the ordinary least square
regression and heteroscedasticity methods. The potential soil physical and chemical
properties were estimated using diagnostic soil survey of simple random sampling
approach. Data were collected from 30 upland maize fields and 30 swamp rice fields.
Crop yields were projected using two Global Circulation Model (GCM) models that
performed best in the study area: CSIRO-RCP4.5 and NOAA-RCP4.5. Climate change
adaptation options were assessed through semi-structured questionnaires with 180
selected households in eighteen communities using multistage sampling techniques. The
results of climate influence on crop yields showed that CO2 and rainfall unfavourably
affect rice yield and were statistically significant. Maximum and minimum temperature
negatively affect yield but not statistically significant at (P < 0.05). The results further
revealed that CO2, maximum temperature and sunshine duration adversely affect maize
yield and statistically significant whilst rainfall and minimum temperature negatively
affect maize yield but not significant at (P < 0.05). Soil survey results indicated that
swamp rice ecologies had high percentage of NPK (N 0.07 %, P 0.0184 % and K 0.04
%) than percentage NPK contents in the maize fields (N 0.06 %, P 0.018 % and K 0.01
%). Soil pH is generally low and ranges from (4.6 to 4.7). The electrical conductivity of
the soils for rice and maize fields are generally high (4.8 dS/m) indicating salt-affected
soils. It is projected that, crop yields showed the percentage mean yield gain for maize
iv
under NOAA-RCP4.5 by 12 % and 41 % but most importantly CSIRO-RCP4.5 by 17 %,
31 %, and 48 % respectively, as the period gets close to mid-century compared to mean
rice yield losses of -19 % and -23 % under NOAA-RCP4.5 scenario. The results showed
that the majority (72 %) of farmers’ use drought-tolerant crop varieties with 67 %
adapting to changing planting date. Majority (64 %) of farmers were forced to fallow
their lands with 40 % of farmers practising petty trading and 47 % depending on temporal
migration as a coping mechanism. It is concluded that rice and maize yield were
vulnerable to climate variability coupled with fragile soil conditions. The future
projection of yields will be inadequate to feed the growing population in the Lower River
Region of The Gambia. There is a need for more adaptation strategies that are compatible
with the local condition that can strengthen the resilience of households to cope with
climate variability. Therefore, climate change adaptation policy should include local
knowledge as a bottom-up approach to enhance their sustainability at the local level.
Description
A thesis submitted to the Department of Civil Engineering, College of Engineering in partial fulfilment of the requirements for the award degree of Doctor of Philosophy in Climate Change and Land Use.
Keywords
An Assessment, Vulnerability of Rice and Maize Yields, Climate Variability, Sudano Sahelian Zone, The Gambia, Drivers and Adaptation Options