1. Introduction
Climate change is among the profound socio-environmental menaces confronting the food and agriculture sector [
1]. In order words, it has had an important effect on food production and agriculture worldwide. The greatest environmental threat facing the globe now is climate change, particularly in Africa [
2,
3]. Climate change is expected to result in volatile weather patterns, unstable growing seasons for agriculture and damaged ecosystems. With severe consequences on natural resources and humans, there is no doubt that the climate is changing [
4,
5]. Truly, as the Earth experiences heat, rainfall profiles drift and lead to extreme occurrences such as flooding (excessive rainfall) and aridity (droughts), coupled with the burning of forests, which recurs continually, thereby resulting in necessitous and unforeseeable harvests [
1]. Evidence of these changes includes temperature changes, erosion, flooding, changes in rainfall patterns, water scarcity, desertification, the outbreak of diseases, land degradation, rising sea levels, poor crop yields, hunger, starvation, decline in economic activities, and pasture losses, among others [
6,
7,
8,
9,
10]. According to Newsham et al. [
11], climate change has serious consequences for the environment and human health, thereby imposing distressing impacts worldwide. The noticeable consequences of climate change in developing countries, especially Nigeria, have resulted in weak and uncertain yields, leaving farmers increasingly anxious and more vulnerable, as they have a low adaptive capacity and rely on agriculture for living [
6,
12,
13,
14,
15]. As a result, climate change has an unswerving effect on production because of the agricultural systems, which are climate-dependent in nature. Consequently, to address this climate change phenomenon, the adoption of urban tree planting is one of the effective approaches that are useful for reducing climate change. According to Ogunkalu et al. [
16], planting trees is an authentic approach for reducing the effects of climate variability.
Urban trees can be defined as all public and privately-owned trees referred to as individual trees along streets, backyards, and stands of residue trees in urban settings and rural areas. These trees are among the planet’s longest-living things and serve as link between the present, future, and past generations. According to Gayo [
17] and Pataki et al. [
18], urban trees are essential for protecting the environment because they provide ecosystem services like clean air, stormwater management, habitat creation and atmospheric cooling. The planting of urban trees is not only for protecting the environment, but also very important in providing health benefits and perceived living infrastructure that offers multiple environmental benefits for residents [
19]. The planting of urban trees is among the best adaptation and mitigation approaches implemented in many developing nations to restrain the undesirable effects of the changing climate [
20]. These reimbursements are called ecosystem services, because they are the means through which urban trees effectively regulate or combat the activities of climate change. The practice of urban tree planting is an exhaustive approach to land-use management, and it is gainful for agricultural production.
Regarding its economic value, urban tree planting is essentially beneficial to the environment and helps in providing abundant tangible and intangible ecosystem services such as nutrient cycling, sink functions of wetlands, and the hydrological cycle [
21]; this, in turn, enhances the maintenance of the environmental quality, ecosystem regulation, and livelihood for both rural and urban dwellers, often at no cost [
22,
23]. According to Burnham [
24], urban tree planting reinforces a range of ecosystem functions and is essential to ecosystems’ ability to adapt. Urban trees dispel climate change through the removal of greenhouse gases (GHGs), changing the urban microclimates through reducing temperatures, altering the patterns of wind, and reducing emissions from energy generation [
25,
26,
27]. Urban tree planting assists in regulating temperatures, reducing energy consumption, improving urban air quality, and reducing wind speeds. Additionally, urban trees help to increase property values, facilitate recovery, and reduce fatigue [
26,
27]. According to Taylor [
28], urban tree planting is the best mitigation approach, given it is more cost-effective than other mitigation approaches as it provides aboveground carbon storage, and cities are advised to adopt it given that cities are recognized as the greatest emitters of CO
2. Despite its contribution, there is a growing experimental understanding of the limitations of urban tree planting as a climate change mitigation strategy.
As a matter of fact, there are a challenge associated with urban tree planting, which underscores it as the perpetual depletion of urban trees in communal landscapes, resulting in a loss of urban trees due to extreme harvests [
29]. From their study findings, Gayo [
17] and Scheid et al. [
30] specifies that majority of the respondents in the region submitted that drought was prolonged as a result of climate change thereby leading to water scarcity and this which limit water intake by urban trees. This further increased the risk of desertification, as well as threatens the planting initiative of urban trees. Few studies conducted on urban tree planting as an approach to further mitigate climate change and to evaluate urban tree planting practices to provide local persons with the capacity and understanding to anticipate productivity. Few studies conducted have focused on farmers’ access to trees and their willingness to participate in tree planting initiatives. Thondhlana and Ruwanza [
31] quantified that there is scanty information existing on the challenges hindering the factors influencing adequate adoption of urban tree planting practices among urban and rural dwellers. Unplanned urbanization and deforestation, among many challenges, have hindered urban tree planting, giving little recognition [
32,
33]. The lack of knowledge about urban trees is also contributing to the limited plantation of urban trees as residents utilize fast-growing, multipurpose tree species, a practice that has been related to failed tree planting attempts and failed attempts to reduce climate change. Hence, this study further focused on the determinants of urban tree planting as a strategy to mitigate climate change.
Thus, there is an urgent need to explore a more sustainable deliberate tree planting approach in the study area with appropriate mechanisms for improving environmental health. It is therefore pertinent to note that no study has been carried out on urban tree planting as a climate change mitigation strategy by households. Hence, the study focused on household-level determinants of urban tree planting as a climate change mitigation strategy in Enugu Metropolis. This study therefore sought to investigate the factors that influence households’ decision in adopting urban tree planting as a climate change mitigation strategy in the region as that would enhance households’ and farmers’ capacity for its adaptation to mitigate climate change issues to necessitate formulation of policies.
3. Materials and Methods
3.1. Description of the Study
This study was carried out in Enugu, the capital city of the Nigerian State of Enugu. The state is geographically located between latitudes 6°21′ N and 6°33′ N, as well as 7°25′ E and 7°38′ E longitudes on the north-west fringe of south-east Nigeria and bordered by the following states which are Abia, Benue, Anambra, Kogi and Ebonyi. Out of the 17 local government areas (LGAs) that made up the state, the metropolitan city is comprised of 3 LGAs, which are Enugu East, Enugu North and Enugu South and comprises of about 722,664 households [
40]. The State’s Forestry Commission under the Ministry of Environment and Solid Minerals is tasked with the duty to manage forestry reserves and tree planting areas. In this regard, this commission has not lived up to this expectation especially in the metropolis, thereby allowing real estate developers and other industrialists the opportunity to determine the topography of the city by uncontrollably felling almost all the trees in a bid to develop the residential or commercial buildings [
41]. This act has further exposed the city and its inhabitants to millions of carbons constantly released into the environment with no remedial plans, programmes or policy. Based on the foregoing and the role trees play in carbon sequestration, this study, which aims at exploring the determining factors of the urban households’ tree planting adoption as a climate change mitigation strategy in the metropolis, is eminently important and evidence-based.
3.2. Sampling Procedure, Frame, and Sample Size
Using a cross-sectional methodology, the study assessed the household features, adoption, and uses of urban tree planting, determinants, and challenges of tree planting in the Enugu state, specifically the Enugu Metropolis. The design was used to collect primary data from farming households that were preferentially selected out of 10 rural communities due to their quite high number of urban planted trees.
The population for this study was sampled using a multi-stage sampling technique. This strategy makes sense and provides an accurate depiction of the intended population. The first stage of multi-stage sampling involved selecting a study site, which is Enugu State. The second stage involves selecting a metropolis made up of the Enugu East, Enugu North, and Enugu South local government areas (LGAs) due to many households’ adapting to climate change, and they are using urban tree planting as a mitigation approach to climate change. Afterward, ten communities were randomly picked from each of the LGAs and six streets were randomly picked from each of the ten communities. The third and last stage involved selecting fifteen households in each of the six selected streets of the ten selected communities that practice urban tree planting on their farms. These households were selected randomly in these 10 communities as they provide different features and benefits of urban tree planting. The sample size for this study was 900 households involved in urban tree planting. However, 823 questionnaires were used for the analysis having discarded 77 for inconsistency. The unit of analysis was farming households.
3.3. Data Collection
In the study, both primary and secondary data were used. Primary data were collected using copies of structured questionnaires to obtain data on households’ characteristics, adoption, and uses of urban tree planting, determinants, and challenges of tree planting. The questionnaire was pre-tested before the actual time of data collection to check its appropriateness and reliability. The researchers made use of well-experienced scholars and extension officers to validate the questionnaire used to gather information. The pre-testing of the questionnaire was also used to train the enumerators who were used to administer the questionnaires. The secondary data were used to write literature and to support the findings of the study. The secondary data used were obtained from peer-reviewed literature, government ghazals, books, and the Department of Agriculture’s records. The data were collected from May to July 2021.
Figure 2,
Figure 3,
Figure 4,
Figure 5,
Figure 6 and
Figure 7 demonstrate peri-urban, urban area and rural areas of Enugu State during data collection by enumerators and researchers. The urban tree plantation in these areas was implemented by the State’s Forestry Commission under the Ministry of Environment and Solid Minerals, which is tasked with the duty to manage forest reserves and tree planting. This was also on the basis of mitigating climate change impact as urban tree planting is providing various benefits. All of three areas have implemented urban tree planting for various reasons depending on the household.
3.4. Data Analysis
Data were coded in MS Excel and transported into SPSS version 23 and STATA 15 for analysis. The study further made use of both descriptive and inferential statistical tools in analysing data. Descriptive statistics were used to estimate households’ characteristics, their uses, the benefits of urban tree planting, as well as the challenges faced by the households. An appropriate econometric model in the form of the Logit model was employed to estimate the factors influencing the adoption of urban tree planting as a mitigated approach to climate change.
3.5. Inferential Analysis and Descriptive Statistics
Using descriptive statistics and t-statistics, it was possible to describe the study variables employed in the logistic regression model to show household problems and understanding of urban tree planting. In order to present the findings of this investigation, frequency tables, cross-tabulations, and graphs were used. In order to analyse the continuous and categorical variables, respectively, descriptive statistics like mean and standard deviation, as well as percentages, were used.
3.6. Analytical Framework
To estimate factors influencing the adoption of urban tree planting as a mitigated approach to climate change in the study area, the Logit regression model was used. The regression model is the best-fit model to estimate the factors when the decision is binary [
42,
43]. Logit regression is a dichotomous analysis frequently used in adoption studies as they are dichotomous. In this study, the logit model was used to analyse households’ decisions in either adopting or not adopting urban tree planting methods as a mitigation strategy for climate change. Logit regression is a statistical method used to predict the relationship between the response or dependent variable in adopting urban tree planting, which has two or more categories with one or more explanatory variables on a category or interval scale.
Comparatively, to discriminant examination, the Logit regression model is more applicable to a larger range of exploration conditions. Due to its superior comparative mathematical simplicity, this model was adopted over the Probit model [
43,
44]. The ability of this model to more effectively address the primary research objectives as well as the characteristics of the data and sample (association between variables, slope indicating how the log odds ratio is in favour of adoption urban tree planting) led to its selection. Furthermore, the significant explanatory variables do not influence household adoption decisions to the same extent. According to Atube et al. [
45], the logit regression model enables binary choice analyses, such as whether or not a household modifies its behaviour to combat the consequences of climate change. This allows the estimation of choice probabilities for the various categories.
Using logit regression, which also satisfies the general normal probability distribution, the heteroscedasticity problem is resolved. The logistic model was consequently used for this inquiry. Let
i stand for the likelihood of success. Think of the collection of explanatory variables
x = (
x1,
x2,…,
xn) as well. These variables could be continuous, discrete, or a combination of the two. In that case, Equation (1) provides the logistic function for
πi:
where:
where:
It is customary to refer to “success probability” as “πi”, where πi is the possibility that a sample would falls into a particular dichotomous response variable category, and 0 > πi > 1. The logistic cdf is represented as Λ(.), where λ(z) = e z/(1 + e − z) = 1/(1 + e − z) and β signifies a vector of variables that need to be evaluated. The odds ratio is the formula .
3.7. Estimation and Likelihood Ratio Test
Although researchers can utilize the least-squares method, the maximum likelihood method is recommended to evaluate
β due to its preferred improved statistical features. The logistic function of the single predictor variable
X in the following logistic model should be expressed as follows:
The goal of the study is to identify the estimations when
βˆ plugged onto the model for
π(
X), and will yield a number near to 1 if urban tree planting is adopted and 0 otherwise. The likelihood function is denoted mathematically by Equation (4):
The estimated values of
βˆ are chosen to optimize this probabilistic function. The study uses the logarithm on both sides to compute and use the log-likelihood function for an estimate. In the investigation, the probability ratio was used to check whether any subset of estimations
β is zero. Suppose that
p and
r denote the corresponding numbers of
β for the entire model and the simplified model. The likelihood ratio test statistic is shown below:
where:
l(βˆ) and l(βˆ(0)) are the log-probabilities of the entire and simplified models, respectively, as determined at the maximum likelihood estimation (MLE) of that simplification. Λ*~χ2 n − r; n and r are the number of variables in the entire and simplified models, respectively.
4. Result and Discussion
4.1. Demographic Features of Farmers
The outcomes of the demographic features of the household heads in
Table 1 indicate that the majority (53%) of the household heads interviewed were males within the average age of 36 years. The study outcomes agree with the findings of [
15,
17,
45], that farming households are dominated by men because of the nature of farming operations, which can be physically demanding, and cultural beliefs in Africa and that can permit men to be engaged in farming, while the women provide some care, handle chores and management of their households. The average age of the respondents stipulates that farming in the study area is practiced by young people who are energized and ready to participate in both environment and developmental preservation. These results concur with the study findings of [
17,
31], that tree planting is practiced by young farming households who are vested with much knowledge about it compared to elderly farmers. The majority (84%) of the farmers attained an educational level of eight years, which is equivalent to secondary years. This explains why the household heads that spent eight years in school have improved abilities to read, as well as their knowledge on agricultural activities, which enhanced their awareness and ability to engage in diverse kinds of farm practice such as tree planting to mitigate climate change. These results align with that of [
46,
47], that being literate as a farming household is beneficial for adopting innovative farming techniques utilized in improving agricultural productivity, since the households sampled can understand, and read the stated instructions. The study results showed that the majority (69%) of the farming households were married and this played a huge role in decision-making, as married farmers thought about the well-being of their households, as well as assisted in the provision of family labour. These results were in line with the findings of [
44]. Household size was employed as a proxy for measuring household labour with the study results indicating that the mean household size was five persons per household, which played an important role in tree planting.
Interestingly, the farming households were working in groups, and this played an important role in enhancing their climate change awareness and adaptation measures available. The study results indicated that the majority (58%) of farming households attained the land tenure status, implying that they were land custodians. The study outcomes further indicated that about 43% of farming households had limited access to extension services, which was a significant factor in their lack of access to information on climate change and effective mitigation measures. The mean farm size of farmers was two hectares and this implies that the households were practicing farming at a small-scale level. These results agree with the findings of [
42] that the majority of smallholder farmers usually have a small farm size. Access to trees was poor (18%) due to its high cost of NGN 500 (0.63 USD) and above (84%) or the high tenancy rate among the farmers. The results found access to climate change information (43%) was very poor and this contributed to the lack of adoption measures in the study. The adoption rate of tree planting as a strategy was found to be 58%, which is low due to the limited availability in their knowledge about climate change, as well as the lack of visibility of extension personnel in the research area.
4.2. Knowledge of the Changing Climate and Its Impact
The results on farming households’ knowledge of the changing climate as perceived by the variations in rainfall and temperatures are represented in
Table 2. The table shows the changes farming households have perceived about climate change. Findings from the study further show that farming households have experienced an increase in temperature, with households experiencing hotter days than they normally perceived in the past years. Farming households have perceived a reduction in rainfall patterns, which has resulted to changes in planting dates. Lastly, farmers have perceived an increase in extreme weather events (drought) and this has negatively impacted tree planting. In their study findings, refs. [
6,
48] made similar observations that these three are the variations from climate change noticed by the farmers.
Farming households have experienced the negative effects of changing climate. Households have also experienced a decrease in production output due to the changing climate. This is due to a reduction in rainfall patterns, which is important for irrigation. These results agree with the findings of Agbugba et al. [
1] and Mdoda [
2]. The decrease in productivity output will eventually lead to a reduction in farm income.
4.3. Uses and Perceived Benefits of Urban Tree Planting by Farming Households
As shown in
Table 3, the majority of the farming households indicated that they were aware of the changing climate factors and their effects on agricultural productivity as it reduces their output and farm returns. Based on the adverse effects, households decided to adapt to variations on climate change by planting urban trees as the mitigation approach. Adoption of urban tree plantation in the study area was well received as socio-economic results pointed out that majority (58%) of the farming households adopted tree planting to mitigate the effects of climate change. Results also indicated that farming households planted various trees due to various benefits, whereas urban trees were planted to prevent the effect of high winds from destroying vegetables and other crops, to protect fodder for livestock keepers, and for building strong shelters for livestock during severe rainfalls, among other reasons. The most understood reason for urban tree plantation was to improve the soil (24%), so that agricultural productivity can be enhanced with possible farm returns. This was also carried out to protect the soil from being eroded during extreme weather conditions as it becomes the permanent soil cover. Findings showed that timber (14%), fodder (20%) and windbreakers were dominant factors in the study area as they provided farmers with counterpart effects of blowing winds, cooling high temperatures and also provided some shelter for livestock. These results were in line with [
17] that tree planting is very important in agriculture, as it yields better benefits for crops, vegetables and livestock keepers. Fruit trees (12%) were planted as they improved some vitamin A status of livestock through grasses and forages besides lowering sensitivity to climate change risks in the area. The results support the findings of Msalilwa et al. [
49], which indicates that this approach is good for livestock keepers; and as a result, their vulnerability to climate change decreases with an increase in output, which will enhance household food security. Moreover, the last reason for tree planting explains why fuel wood and fencing by households since they are widely used under minimal circumstances for income generation purposes.
4.4. Determining Factors of Households’ Urban Tree Planting Adoption Decision
The study employed logistic regression to evaluate the factors that affect farming households’ decision to adopt tree planting in the Enugu metropolis. Findings as indicated in
Table 4 showed that sixteen parameters were used in the model, while only eight parameters were discovered to be significantly related to the decision to implement urban tree planting by farming households at different probability levels.
Table 4 displays specifics of relevant factors from this model. The corrected R
2 of the regression was 0.723, which indicates that the regressors included in the model can account for 72% of the dependent variable’s variation. The more explanatory and better the model matches the sample, the higher the R
2 value. The influences on household adoption of urban tree planting are shown in
Table 4.
Education had a coefficient that was positive and was found to be statistically significant at a 1% level of confidence, indicating that an extra year of education for households will result in a rise in the adoption of urban tree planting. This, therefore, implies that an increase in education will enhance households’ knowledge about innovative techniques that are employed in agriculture to mitigate climate change. This is because educated households have more environmental consciousness and a higher knowledge level attained through the formal education system. These results agree with the findings of Lockwood and Berland [
48], which indicated that educated households in Central Indianapolis are vested with more knowledge about urban tree planting as a climate change mitigation strategy as it enhanced their productivity. The marginal effect implies that an extra year of education for the farmers will result in a 2.3% rise in the number of households adopting urban tree planting as an approach to mitigate climate change.
It is worth noting that the price of tree seedlings had a positive coefficient, which was found to be significant at the 1% level. These outcomes imply that a 1% rise in the price of tree seedlings will result in a rise in urban tree planting adoption by the households. Hence, the price of tree seedlings determines the quality of the urban trees that households purchase. A low-priced urban tree is associated with poor quality, which means the households will not enjoy their benefits unlike when the quality is good. Gayo [
17] made a similar observation that the cost of urban tree seedlings determines the sustainability of the urban tree, as well as the quality of the tree and that will enable households to enjoy productivity in their agricultural practices. The marginal effect implies that there is a 1% increase in the price of tree seedlings, which will lead to a 4.2% increase in households’ chances in adopting urban tree planting as an approach to mitigate climate change.
Regarding access to climate change information, it indicated a positive coefficient was found to be significant at 5% confidence level. This implies that a 1% rise in access to climate change information by households will result in households’ urban tree adoption as an approach to reduce climate variability. This is because households are equipped with the necessary knowledge about climate change, which enhances their decision to adapt to it by adopting sustainable strategies that enhance agricultural productivity and farm returns. In order words, access to climate change awareness has improved the adaptation rate and improved the level of understanding of the approaches to be used by households. The marginal effect infers that a 1% rise in climate change information access by the households will lead to the rise in their urban tree planting adoption, which is an antidote approach to reduce climate variability by 3.0%.
More so, the use and access to trees had a positive coefficient and was found significant at a 1% confidence level, which infers that a 1% increase in understanding the use and access to trees by the household will induce an increase in adopting urban tree planting as a strategy to reduce climate variability. This is because households understand urban tree benefits from other farmers and have access to such information, which makes it easier for them to adopt urban tree planting as a formidable strategy. Understanding the benefits of urban tree planting will make it easier for households to adopt them as they are well informed of the benefits. The marginal effect implies that a 1% increase in the use and access of trees will increase households’ chances in adopting urban tree planting as an approach to mitigate climate change by 5.6%. In his study on tree planting, Gayo [
17] made a similar observation.
At a 1% level, occupation had a significant and positive coefficient. This is positive because employed persons have no time to seek knowledge about the tree benefits as compared to self-employed and informal employed. This suggests that a 1% unit increase in informal and self-employed, will induce an increase in adopting urban tree planting as a mitigation strategy for climate change. This is the case as employed persons spent less time on tree planting than self-employed persons and do not seek the benefit of planting trees. Flexible time for self-employed households allows them to have time to understand tree planting as well as to know the requirements for planting trees to enable them to reap the highest benefits. The marginal effect implies that a 1% increase in occupation will increase the chances of households adopting urban tree planting as an approach to mitigate climate change by 4.2%.
On the other hand, respondents’ age is particularly important as it is used as proxy for measuring farm experience. Age had a negative coefficient that was found to be significant at a 5% confidence level. This infers that as households increase annually, it will result in a decrease in the adoption of urban tree planting as a strategy for reducing the effects of the changing climate. This is the case with experienced farmers who are vested with knowledge on the strategy on what suits their farming profession since they have been farming for years and only care about providing food for their households. The study had many inexperienced farming households, which affects the adoption of urban tree planting as they do not know what approach to use in their farm. The marginal effect implies that a 1% rise in the respondents’ age will result in a reduction in households adopting urban tree planting as an approach to mitigate climate change by 3.4%.
Furthermore, at a 5% level of significance, the positive coefficient and statistical significance of access to sufficient water were both present. This suggests that increasing family access to appropriate water will lead to a rise in the usage of urban tree planting as a climate change reduction strategy. This is because water is essential for irrigation purposes as it assists in the growth stages of trees. Therefore, having access to adequate water enhances the growth stages of trees. Hence, the marginal effect implies that a 1% increase in the access to adequate water will result in households adopting urban tree planting as a viable option in mitigating climate change by 1.9%.
4.5. Study Implication to the Broader Overview of Urban Tree Planting
The study presents the current status of urban tree planting and its importance in reducing climate variability impact. The study further revealed that climate variability poses a major threat that poses a negative impact on the livelihood of the peri-urban and urban populations of developing countries, especially Nigeria. Climate change has severe consequences on natural resources as the earth experiences heat, rainfall profiles drift, and utmost occurrences such as aridity (droughts) and floods (excessive rainfall) coupled with the burning of forests, which negatively impacted economic activities in urban and peri-urban areas such as a decline in agricultural practices and land degradation. This decline in economic activities resulted in the loss of income, productivity and employment for many persons who depend solely on agriculture-related careers for living.
Adaptivity to climate change is the only feasible approach in mitigating climate change in developing countries. This approach will provide farmers and farming households with a resilient approach that will enhance productivity, which plays an important role in reducing food insecurity and poverty, which is extremely high in developing countries. Tree planting is one approach that is easy to implement and affordable to any household and farmer. Urban trees seem to be a more visible choice for adapting to pollution and climate change than mitigation measures. Tree planting is not only used as a mitigation strategy, but also for the reproductive capacity of farms and their usage as a source of food. Urban tree planting provides countless ecosystem services and social benefits to urban inhabitants.