Climate Change Impacts And Adaptation Barriers Among Smallholder Cassava Farmer

Climate variability/change has varied impacts on crop yields in many Sub-Saharan African countries. Enhancing the adaptive capacity of rural farmers is a major challenge as climate change becomes threatened to agricultural activities in the region. In this study, the impacts of climate change on cassava crops were examined, and farmers’ perceptions of climate, change and their experienced adaptation methods were assessed. Historical climate data and social datasets were used; the adaptation option and barriers to the use of adaptation methods were obtained through questionnaires, semistructured interviews and focus group discussions. Correlation statistics and multiple regressions were utilized to show the impacts of climate on the yield of cassava. The results showed a high variation in climatic variables together with an obvious anomaly index with severity. Minimum and maximum temperatures correlated strongly and positively with the yield of cassava, with 0.86, 0.82 and 0.87, respectively, which were signicant at p>0.05. The results of multiple regression showed that climate parameters accounted for 75% of the changes in yield. The results also showed a very strong relationship between crops and rainfall in the early growing season at the p<0.05 level of signicance. The majority of the farmers perceived that lack of capital and nancial, physical and human capital accounted for 70% of barriers to the implementation of climate change adaptation methods. The key ndings here are that the cropping system has been impacted by climate change and that the adaptive capacity of rural farmers in the study area is generally low. The study concludes that although climate change is obvious, there is generally a need to enhance the adaptation options available to farmers in the region.

in uence crop production [4,12,13]. Additionally, rainfall at the onset and at the closure months of the growing season has been found to be important at the optimum temperature. Studies reveal that climate change generally occurs in rainfall and temperature, as climate determines water availability for the growth and production of crops, which directly affects the yield of crops. Rainfall is important for the stability and quality of yield and can also be a threat to the yield, especially for cassava, as reduced or erratic rainfall during the germination growth stage and the development of tubers can result in decreased yield, just as temperature can encourage the growth of weeds and pest proliferation, thus leading to a reduction in yield [14].
In Nigeria, the production of cassava was originally for food, as it is a source of different indigenous diets, such as gari, eba, fufu, and amala [15][16][17][18]. Today, cassava has been commercialized following the advent of cassava usage in the production and processing of animal feed, raw material for starch, and ethanol for industrial uses, among others, leading to the exportation of approximately two-thirds of cassava produce not only in Nigeria but also in many countries in SSA [19][20][21][22][23]. Since it is a crop that grows even on poorly drained soil and has less demand for fertile soil and rainfall compared to other crops [24], it is widely grown for different purposes almost everywhere in Nigeria to meet local food demand and with many into commercial production for export. The production of cassava is concentrated in the hands of numerous smallholder farmers in the central and southern regions of Nigeria producing different varieties of cassava [25,26]. The cropping of cassava has transitioned from traditional production systems to the use of high-yielding varieties and mechanized production and processing. Cassava is a crop of tropical lowlands, and it is restricted to regions that lie within latitudes 30 0 north and south of the equator with a higher concentration near the equator [27]. It thrives under humid-warm climatic conditions with temperatures ranging between 25 0 -29 0 C and precipitation of approximately 1000-15000 mm, which ideally should be evenly distributed throughout the growing season. However, cassava has an enormous ability to adapt to different climatic conditions, as it can survive high temperatures of approximately 37 0 C and low temperatures of approximately 17 0 C [28].
The demand for cassava and its products locally and internationally has necessitated an increase in the growth of the crop even in many regions, making it one of the most cultivated crops in SSA countries across different ecological zones [29][30][31]. Cassava production has been greatly impacted by changing climatic conditions in the country amidst other challenges of cultivation, with no substantial establishment of how it has been impacted by climate well documented in the literature. Hence, this study examines the impact of climate change on cassava crops in a state in Nigeria. Farmers' perceptions of climate, experiences, and adaptive capacity were assessed with the aid of a well-structured questionnaire, semistructured interview and focus group discussion. Climatic data, crop yield data and social data from the questionnaire were analysed using both descriptive and inferential statistics. This study involves the perception of the climate and adaptation capacity of farmers.

Study sites
The study sites were among rural farmers in rural communities (Table 1) in freshwater ecological zones situated in Ogun state, Nigeria. The state ( Figure 1) is a home of some agricultural produce, with a total land area of approximately 17,000 square kilometres located between latitudes 6 0 12'0"N and 7 0 47'60"N and longitudes 3 0 0'0"E and 5 0 0'0" east of the Greenwich Meridian [32]. The area is typical of a tropical climate consisting of two different seasons of wet and dry conditions. The wet season is relatively associated with the dominance of the moist maritime southerly monsoon from the Atlantic Ocean, while the dry season is predicted by the continental northeast trade wind from the Sahara Desert. The average temperature value varies according to the months and can be 25.70°C in July and 30.20°C in February. The selected state is ranked among the top agrarian states in Nigeria with similar agricultural practices and methods of cassava crop production.
The major occupation of the people of Ogun state is agriculture, which has employed many people, especially those in rural regions. The state is also known to have many educational institutions that employ many. Several other identi able modern economic activities exist in Ogun state, and these include insurance, motor companies, petrol stations, light and heavy industries, which also employed a good number of the populace [33].

Sources of Data and Analyses
Climatic datasets, rainfall, minimum and maximum temperature, were sourced from the archive of the Nigerian Meteorological Agency (NiMet). Oshodi and NiMet used the British Standard Rainguage and Dine's tilting siphon rainfall recorder for rainfall and thermometer. To address the rainfall variability in this zone, we considered the number of rain days, various growing seasons and total rainfall (mm) for each year. In this study, a year is divided into two growing seasons. These seasons are (1) the early growing season from April to June) and (2) the late growing season from July to October. Crop yield data were sourced from the Ogun Agricultural Development Programme (OGADEP), which was derived by dividing the total cassava output by the area of farmland. On the other hand, social data were sourced primarily from farmers with the aid of a well-structured questionnaire, the Semistructured Interview and Focus Group Discussion (FGD), which were purposively administered to farmers to assess the practice of selected adaptation options as well as barriers. The targeted population for the study was farmers who were 30 years and above. This limit is to obtain data only from experienced farmers who have witnessed different farming seasons. Sampling and sampling locations are presented in Table 1 and Figure 1. Three FGDs with 6 semistructured interviews (SSIs) were conducted to assess the farmers' perceptions of climate and experience. Content analysis was performed to assess the cropping experiences of farmers. The historical pro le of the settlement (study area) was collected from the high chief of the settlement, while tent to tent participatory oral interviews were conducted for each farmer in the settlement. The results of the FGD and SSI were analysed using content analysis, while the data from the questionnaire were analysed using descriptive statistics involving frequencies and percentage error graphs to present the adaptive capacity of farmers and barriers to adaptation.
A line graph was plotted using SigmaPlot 10.0 to show changes in climate parameters, while the standardized anomaly index (SAI) was used to assess the annual variation from the mean. Sunburst diagrams and linear dendrograms were used to illustrate social data. The SAI has become the most popular precipitation and temperature index based on hypothetical development and usefulness for analysis [34,35]. It presents the number of standard deviations from which a climatic record is above or below the climatological average for a station of a particular location. This study employs the use of annual data to calculate the anomaly index as given by the formula in equation 1.
where (α) is the gamma function, and the two parameters α and β are the scale and shape parameters of the space under consideration, respectively. The calculation of the parameters was obtained for each location on the annual scale. To estimate the parameters, a probability weighted moment was employed using the classi cation of the anomaly index shown in Table 2. Pearson correlation was used to assess the relationship between crop yield and climate variability. The relationship is as expressed in the equation below: where N is the number of pairs of scores, ∑ xy is the sum of the products of paired scores, ∑ x is the sum of scores, ∑ y is the sum of y scores, ∑ x 2 is the sum of squared x scores, ∑ y 2 is the sum of squared y scores, x is the crop yield and y is the climate data. Multiple regression was performed to nd the combined impact of climate on each of the crops. With the use of climatic (temperature and rainfall) data, the impacts of climate on crop yield were established with the use of multiple regression. The formula for regression is as shown equation 3: where Y= dependent variable, X = independent variable and b= the slope of the line and a = y-intercept.

Climate parameters and anomalies
The results revealed high variations in rainfall and temperature both annually and monthly during the study period (Figures 2 and 3). There is high variation in climatic parameters, as shown in Figure 1, which can be linked to global climate change. Signi cant annual variations in rainfall were observed for each year in relation to annual total rainfall, corroborating the ndings that there is variability in several rainfall events recorded at several stations in Nigeria [36]. Climate variability, as documented in a part of Nigeria, among several other places globally, can cause negative departures from the normal climate. Rainfall is associated with SST, as equatorial Indian Ocean SSTs strongly in uence rainfall variability in Nigeria in conjunction with the role of the ITD, as the equatorial displacement of the Atlantic subtropical high suppresses the northward summer migration of the ITD, thereby resulting in rainfall variability [37].
The standardized anomaly index (SAI) of annual rainfall and temperature is shown in Figure 3. Categorization around zero is an indication of normal precipitation or temperature, while those markedly above or below zero indicate relatively wet or dry conditions ( Figure 3). The maximum temperature was above normal in the rst and second decades, moderate in the third decades and has increasingly furthered below normal since the fourth decades. The minimum temperature was generally above normal in the rst to the middle of the second decade, moderate to the middle of the third decade and tended farther below normal. Meanwhile, the rainfall was generally far above normal from the early years covering the study period and about normal to the middle of the second decade after which it went far below and above normal in consecutive years, moderate till the middle of the third decade which went far below normal in 2005 and with adjustment about normal until it was far above normal in 2012 and falls below normal in the consecutive years.

Changes in yield as evidence effects of climate on cassava
The results of the bivariate correlation analysis between the annual minimum temperature and crop yields during the growing season are shown in Table 3. There is a strong and positive correlation between the yield of cassava and rainfall, cassava and minimum temperature, cassava and maximum temperature. However, signi cant relationships were recorded for the minimum and maximum temperatures and the yield of cassava. The results of the yield of cassava, rainfall, minimum and maximum temperatures when combined showed 0.75, i.e., accounting for over 75% of changes in crop yield, while the remaining 25% can be explained by other variables, such as edaphic and cassava resistance factors (Table 3). Reduction and erratic rainfall both negatively affect the yield of crops, and the relationship between climate and crop production in Nigeria has been reported to vary depending on the type of crop, seasonal properties and life cycle of the crop under consideration [38 -40]. As shown by the results in Table 3, rainfall had a strong relationship with crop yield during both the early and late growing seasons, with R > 70%. The results further showed a very strong relationship between crops and rainfall in both early and late growing seasons (Table 3). Previous studies have reported that rainfall can be maximized for crop production only when temperature and relative humidity are at high levels. While rainfall variability is capable of in uencing maize yield, it was reported that temperature is capable of contributing approximately 50% to changes in yield; relative humidity can bring about an increase in yield when it is usually high throughout the growing season. The relationship is, however, in uenced by the level of inputs [41,42]. Despite changes in climate conditions, the study found an increase in cassava production, as illustrated in Figure 4. Yet, earlier study have shown that long dry spells combined with high temperatures can have a severe in uence on yield, since the effects of rainfall and temperature on tuber crops are clear, particularly for cassava, which can reach 95% probability levels [43,44]. Because rainfall volume and frequency during the time immediately following planting affect yield, an increase in land committed to cassava production may not result in a comparable increase in yield. Although, cassava is less sensitive to rainfall at the start and end of the growing season, several factors can account for a reduction in cassava yield, as both reduced and erratic rainfall can affect yield, but it also depends on the level of inputs, such as fertilizer and the planting of resistant species [14]. With the introduction of climate-smart cassava varieties and the liberalization of the seed value chain, which enhances the availability of improved seeds to farmers, it is possible to boost yield even with a reduction in land area [44][45][46]].

Practice of adaptation and adaptation options based on gender
Adaptation practices have been reported to be dependent on the age of farmers, farm size and level of production. The study observed that despite the statistical evidence of changes in climate parameters, yield increased. The practice of adaptation option is shown in Figure 5. From the gure, mixed farming planting of different species or varieties, agricultural intensi cation, bush fallowing, changes in seasonal timing of sowing and harvest and the use of credit facilities actually helped enhance the yield of cassava over the study period. There has been an expansion on adaptation to current and projected impacts of climate change to include barriers to adaptation, and these have raised questions around social, nancial, cultural, environmental and ecological conditions and changes that can hamper the ability of a farmer to adapt to climate change [47].
The study further examined the causes for the low level of adaptation, and the results of the broad obstacles to adaptation method adoption in the study area. It is obvious from Figure 6 (Figure 6).
In particular, the perceptions of climate change impacts, adaptation and barriers to adaptation methods vary by gender (Tables 4 and 5). Nearly 65% and 35% of farmers in the study areas are male and female, respectively, in terms of population. Adaptation practices by rural farmers based on gender differed much more, but both perceived that the temperature of the hottest month was believed to be warmer by a higher proportion of the respondents. Many think that extreme oods are more frequent, while extreme drought and the durations of the rainy and dry seasons have remained the same. The farmers' perception of lack of capital is probably responsible for low adaptation practices in the study area. Generally, their adaptive capacity is low, although the most practised adaptations were irrigation, use of loans and credit facilities, agricultural intensi cation, and agroforestry, among others. Additionally, climate change, societal change and ecological change have led to farmers abandoning some landrace crops, such as palm produce, cocoyam and water yam, which are considered to be less productive, and they have adopted new crops, such as water melon, cucumber and pepper, based on market demand. The majority of the farmers are not practicing speci c adaptation methods, and the study investigated barrier adaptation and found that a lack of nancial, natural, social and physical capital is generally a barrier to adaptation, although some deliberately have not taken any measure or have chosen not to practice adaptation (Table 5). Earlier studies have reported climate change adaptation differences by gender. The majority of them stated that farmers' adaptation strategies are said to vary according on their gender, age, farm size, and farming experiences. In the present study however, barriers to adaptation have been added to the discussion of adaptation to current and future impacts of climate change, raising questions about social, economic, cultural, environmental, and ecological factors and changes that can impede a farmer's ability to adjust to climate change [47,48]. Generally, most farmers in Africa have already perceived an increased temperature coupled with insu cient precipitation for production. However, studies have indicated that approximately one-third of farmers in Africa have not changed their farming techniques despite their perception of climate change, which is high for reasons unknown [31,43]. Climate change, market demand and societal change have led to different farmers abandoning some landrace crops. Different adaptation options were assessed, and the results varied spatially, as the level of adaptation was highest in Ondo, followed by Kwara and lowest in Ogun state. The most practised adaptation options are agroforestry, changes in harvest time, securing loan and credit facilities, agricultural intensi cation and irrigation. However, the results also showed that the adaptation levels of the farmers across the three ecological zones were generally low. Additionally, the results of barriers to adaptation showed that the barriers to adaptation are primarily on capital in different forms, such as human capital, nancial capital, natural capital and social capital.
Gender has been identi ed to play a critical role in the use and practices of mitigation and adaptive measures of climate change in many societies due to indigenous knowledge and leadership in sustainable resource management, leading sustainable practices at the household and community levels.
Poor women's participation at the political level has resulted in greater responsiveness to citizens' needs and has been increasing cooperation across party and ethnic lines and delivering more sustainable peace. The impact of climate change will be disproportionally harsh for the poorest countries and the most vulnerable people and groups, particularly women [49]. It is therefore important to recognize the adaptation capacities of both males and females to understand gender-based adaptation differences since climate change affects men and women differently. Women who receive less education tend to be poorer, and in the decision-making process, they are usually excluded at both the political and household levels. Notably, the present study assesses gender differences in adaptation and barriers to adaptation, as presented in Tables 4 and 5.  Other adaptation with similar purpose preferred 37.5 62.5 Incompatibility of tradeoffs 50 50 Fear of potential risks or adverse effects 60 40 What is obvious from the results of this study is that the relationship between climate change and crop production in Nigeria varies depending on the type of crop, seasonal properties and life cycle of the crop [50,51]. Generally, the climate change effect was found to be pronounced on the output of crops, as an increased occurrence of dryness in terms of elongated spell length is capable of reducing yield [52][53][54]. Climate variability has implications that are signi cant for global and regional food production, for which the extent of the impacts remains uncertain to an extent, as the impacts of climate variability on some common classes of food crops, including tubers, grains, legumes and vegetables, vary as the mean temperature and moisture requirements vary with tuber crop production.

Conclusions
In this study, the observed impact of climate change on cassava crops was examined, and rural farmers' perceptions of climate, experiences, and adaptive capacity were assessed with the aid of a well-structured questionnaire, semistructured interview and FGD. It was observed that the rainfall and temperature were markedly with high variations, which also correlated strongly and positively with the yield of cassava. However, the study observed a general increase in the yield of cassava throughout the study, which is occasioned by fair practice of adaptation measures, especially the introduction of improved species of cassava that takes less time to maturity when compared with the local species grown in the past, although adaptation practices are generally low among the farmers. The study recommends enhancement of adaptation options available to farmers in the region for better yield to unlock new business opportunities for the country through cassava processing.
A signi cant number of farmers interviewed during the FGD of this study already believed that temperature has increased and rainfall has declined, with those with a high experience of farming likely to notice climate change. However, there are differences in the ability of farmers to adapt, as their adaptive capacities vary signi cantly. Generally, climate change is a reality, and its effect has negative impacts in Africa, leading to food shortages [55]. However, climate change awareness and adaptive education through extension workers have helped farmers cope with the menace of climate change. As warming poses a high risk to agriculture, irrigation, multiple cropping and integration of livestock will bene t most African farmers. Better access to markets, extension and credit services, technology and farm assets (land, labour and capital) are also effective adaptation measures and have been ongoing in Africa [56]. Given the observations in this study, the following recommendations are made with regard to the impact of climate on crops in selected ecological zones in Nigeria. Although the government, international bodies and local organizations are funding adaptations through loan and credit facilities to farmers, this is still inadequate. Therefore, there should be better participation to curb food insecurity challenges in Nigeria in general and speci cally in the study area, including Ondo, Ogun and Kwara states. Farmers should engage in planting crops that require more moisture in the late growing season, which, as revealed by the study, has more moisture than in the early growing season, while crops that can endure or require higher temperatures should be grown in the early growing season. The study showed that maize is less sensitive to climate, unlike rice and cassava; farmers should engage more in growing maize to enhance their yield.
The challenge of improving the yield of staple crops such as maize, rice and cassava in Nigeria is generally heightened by the increasing temperatures and unpredictability of rainfall. Climatic records should therefore be made available to farmers, and predictions and forecasts for farming seasons should be made available to better prepare farmers for uncertainties to come. Early planting portends dry spells for maize and rice. It is therefore recommended that farmers who will engage in early planting of these crops should make use of irrigation options for better yields, as dryness and hot spells can follow the rst, second and third events of the year, which can even in uence temperature, thereby exposing crops to severe conditions. The loans and credit facilities through the government and her agents do not get directly to local farmers. As claimed by their farmers, it is only the rich farmers that can assess government farm inputs. There is a need for affordable and available improved seedlings and a variety of crops that can adapt to diverse climatic conditions. Importantly, the government, through her agencies such as the extension workers of the Agricultural Development Programme and corporate organizations, should engage more in sensitizing farmers about climate change and the need to adopt coping strategies for enhanced yield. Farmers generally depend on rain-fed agriculture; therefore, short-term uctuations in weather patterns have signi cant impacts on their cropping activities. There is a need for adjustment to short-term anomalies within a reasonable economic and technological limit. To assist farmers in better coping with climate variability and potential long-term climate changes, government policies must address and increase farmers' prospects for better adaptive responses while enhancing the availability and affordability of inputs such as fertilizer, seedlings, pesticides, and herbicides.

Declarations
Availability of data and materials The underlying data can be made available upon request to the corresponding author.

Ethics approval and consent to participate
This study conforms with the ethics principles of Obafemi Awolowo University. Ethical approval for this study was obtained with standard ethics as the participants were not vulnerable in anyway, data was processed in anonymous procedure, and survey participants had the possibility to skip questions.

Consent for publication
Not applicable, because there is no data contained within our manuscript from which individual patients or participants may be identi ed. Practices adaptation methods for rural farmers Figure 6 Barriers to practicing adaptation in percentages ranked by farmers