Population increase, agricultural productivity and environmental degradation have characterized many developing countries including Tanzania. These trends have negatively impacted on development and natural resources, amidst the increasing demand for resources in the wake of ever increasing population. Environmental degradation in several parts of Tanzania not only affects biodiversity but also has a direct impact on water quantity and quality, livelihood, poverty and development of a nation.
The Tanzanian population increased from about 12 million people in 1967 to 44.9 million in 2012, almost four times. With the annual growth rate of 2.7 percent, Tanzania’s population is projected to reach 69.1 and 129.1 million in 2025 and 2050 respectively [1]. Population growth, in both rural and urban areas, is the underlying factor behind rapid rates of deforestation in Tanzania. Population growth escalates the requirement for basic needs such as food, shelter, infrastructure development, fuelwood, furniture, construction materials and other products. In meeting these accumulating demands, deforestation is inevitable. The impact of population growth on deforestation is worsened by the reality that the growing population remains in poverty with limited livelihood strategies and, therefore, compelled to undertake unsustainable economic options including deforestation.
Tanzania is facing an unprecedented loss of its forests and other woodlands. Over the last three decades, blocks of forests in Tanzania have been heavily impacted by official forest excisions as well as illegal, irregular and unplanned settlements. Evaluation of vegetation cover change based on time-series satellite images and repeated aerial surveys showed that between 1990 and 2010, the country lost an average of 403,350 ha or 0.97 percent per year and also, between 1990 and 2010 the total loss was estimated to be 19.4 percent (about 8,067,000 ha) of the forest cover [2]. Within this period, Tanzania was, among the ten countries that had the largest annual net loss of forest area. A recent report indicates that the country had already lost about 38 percent of its forest cover [3]. According to the report, the rate of loss is 400,000 ha per annum and, the risk is deemed high as the country’s entire forests can be depleted within the next 50 to 80 years if the current trend remains unabated.
Although there are information gaps for some disciplines on a sustained basis, already links have been suggested between population growth, land cover change, land degradation and an acute shortage of water [4]. Among the reasons for desertification caused by population growth are deforestation, overgrazing and overcultivation. Expansion of agriculture, especially the massive clearance of land for cultivation of cash crops such as cotton and tobacco to increase export earnings has been mentioned as one of the leading causes of deforestation in Tanzania [5].
While data for various land vegetation in Tanzania from 1990 to 2010 indicate the declining trend for forests and other wooded lands, subsistence agriculture alone is responsible for 48 percent of deforestation while commercial agriculture contributes 32 percent [6]. In Tanzania, the impact of agriculture on deforestation (see figure 1) is affected by a number of factors including human population growth, poverty and government policies. Human population increase translates into the expansion of land under agriculture in forest areas in order to meet the growing requirement for food and income. As pointed out earlier, poverty is linked to incapability to afford the agricultural inputs for bumper crop production. Consequently, people are forced to abandon the existing farms and clear virgin forests for new farms, the practice commonly known as shifting cultivation. To farmers, virgin forest lands have a number of advantages, making it less laborious. Virgin forest soils are easy to work with; new farms are more fertile and productive; after clearing, the area is burned and is ready for planting; new farms have fewer weeds for about two seasons. Therefore, weeding is very much reduced; new farms are less infested by pests; newly cleared forest soil is well drained and requires zero or minimum tillage before planting [7].
With reference to the 2002-2012 intercensal period, Tabora region’s 2.9 percent average annual population growth rate was the 9th highest in the country [8]. It was also the 24th most densely populated region with 30 people per square kilometre. Census data for the last two decades indicate a dramatic population increase in Tabora region. The projections show that population growth rate will increase from 3.8 percent in 2003 (with a population of 1,777,437) to 3.9 percent in 2025 (with a population of 4,181,327) [9]. The rapid population increase since 1980 has occurred mainly due to the influx of farmers, attracted by fertile forest soils and improving infrastructure. The demand for water and other natural resources to serve basic needs is growing steadily as the population continues to increase. This is putting tremendous pressure on what are already scarce and highly vulnerable natural resources. Tabora region’s land converted from natural vegetation to cultivated land between 1984 and 1995 was 4.7 percent compared to 11.2 percent that was converted between 1995 and 2000 [10]. There is a total of 33 Forest Reserves which have a total area of 3,422,500 hectares out of which about 119,691 hectares are catchment forests, and as of now about 201,017 hectares have disappeared through encroachment [11]. As a result of the high deforestation rate and subsequent fire-based agricultural land preparation with little or no fertilizer input, soil fertility has declined tremendously in the area. Natural secondary succession in the left bush lands and grasslands is also prevented by constant annual recurrence of fire.
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The inner model suggests that of the three direct determinants, attitude toward the behaviour had the most substantial impact on farmers’ intentions to adopt a behaviour of planting trees, producing a change of 0.421 units in behavioural intention for each unit change in attitude. This influence on intention is more than twice that of subjective norm (0.213) and more than three times that of perceived behavioural control (0.138). This finding suggests that farmers’ decisions about tree planting are influenced strongly by their view of its value, moderately by the opinions of significant others, and weakly by farmers’ perceived ability to do so.
The coefficient of determination, R2, is 0.46 for the Intention endogenous latent variable. This means that the three latent variables (Attitude, Subjective norm and Perceived Behavioural Control) moderately explain 46 percent of the variance in Intention while Intention itself explains 82 percent of the variance of Behaviour.
The findings of the survey were reinforced by the outcomes of the focus group discussions. During the group discussions, farmers were asked to point out the most important barriers that hinder tree planting among people in their villages. Interestingly, the most important barriers cited were laziness, land scarcity and lack of tree seeds. Farmers explained that planting and caring for trees is labour intensive and because of many other responsibilities around the farm and the house, some were not motivated to take on tree planting on top of their other duties. Others might have been unsuccessful with tree planting activities in the past, and were therefore seen to be disinterested in any further tree planting activities.
The study probed for the reasons behind the fact that large parts of Tabora region have already been denuded of trees and still people cut without planting. A farmer at Ilagaja village, Nzega District reported that ‘fuelwood gathering has been responsible for deforestation and environmental degradation’. She further narrated that ‘some fuelwood, however, is used for village industries including tobacco curing and burning bricks’. Within the same focus group discussion, another participant reacted that ‘fuelwood gathering is probably a less important cause of deforestation than land clearing for crop production’. This response was echoed by another participant who said that ‘production of charcoal for sale is probably a much more severe cause of deforestation than firewood gathering for home consumption in rural areas, because charcoal burners cut the whole tree’.
One of the factors that the participants mentioned and that could pose as a barrier in the adoption of farm level tree planting is cultural practices (taboos). A 42-year-old male farmer in Ngwatu village (Nzega District) said: ‘Many farmers in our village do take care of sacred trees for worshipping and other rituals. Other types for domestic and other uses receive less attention.’ A 47-year-old female in Mitowo village (Sikonge District) put it succinctly: ‘These trees are not allowed to be cut unless under special circumstances, especially for ritual purposes or for treating be-witched persons.’ A female youth in Mitwigu village (Sikonge District) said: ‘Some trees are left on the farms during land preparation or harvest for provision of fruit/food, medicines, shade or use in rituals and some are left in the farm because it is believed that they protect the harvest in the field from witchcraft.’
FGDs of farmers expressed hindrance in tree planting operations and the harbouring of cultural beliefs as having negative impacts since they have strong influence on agroforestry uptake. They are powerful determinants of peoples’ actions, and often hold more local influence than rules and legislations set by national governments. However, these beliefs were outweighed by their perceptions of positive impacts.
FGDs also provided interesting insights into the proportion of households where the household head is the main decision-maker. For decisions on activities such as planting, sowing, and weeding of crops, the main decision-maker is the household head in about half of the households sampled (this does not seem to differ between male- and female-headed households.). For tree planting and tree management, however, the household head is more often the main decision-maker in male-headed households and less often in female-headed households compared to the other activities. For most agricultural activities, the decision-making pattern was a mix of decision-making by the husband, the wife, or by both.
As an alternative to the escalating fuelwood problem in the Tabora region of Tanzania, farmers are attracted to woodlots. Tobacco farmers in Tanzania used to get all of their firewood from the miombo woodlands, but this is no longer the case as deforestation takes its toll. An FGD participant in Mitwigu village, Sikonge District confirmed that ‘farmers are now slowly opting for alternative sources of fuelwood such as having an on-farm supply, hence the interest in woodlots’.
Following reports from the FGDs, physical observations of on-farm tree planting in the two districts suggest that intercropping the nitrogen fixing tree Leucaena leucocephala with maize provides the farm family with sufficient fuelwood in addition to supplying the maize with nitrogen.
1. Discussions
Results of the survey revealed that the ‘Attitudes’ had the highest standardized effect on intention toward tree planting behaviour followed by ‘Subjective norms’ and lastly ‘perceived behavioural control’. This observation confirmed the findings of [71] in other domains. The effect of ‘Attitude’ to ‘Intention’ and ‘Behaviour’, and the effect of ‘Subjective Norms’ to ‘Behaviour’ as well as ‘Perceived Behavioural Control’ to ‘Behaviour’ were significant at (p < 0.001, p < 0.01 and p < 0.05 respectively). Like [71], the results of this study revealed that intention was a significant predictor of the behaviour. Findings revealed that attitude was a positive predictor of intention. There was also evidence that attitude itself was a stronger predictor of tree planting behaviour. In other words, participants with more positive attitudes toward tree planting also had greater intentions to engage in the behaviour.
In evaluating inherent human behaviour towards tree planting adoption in Tabora region, respondents believed that ‘Attitude’ to adopt or not to adopt tree planting (SNs) significantly influences their adoption behaviour (H2). Attitude which in this study yielded a path coefficient of 0.421 has been proposed in several studies using different theories to influence behavioural intentions [40]. Respondents also believed that perceived social pressure to adopt or not to adopt tree planting (SNs) significantly influences their attitude toward adoption (H3) with a significant path coefficient of 0.213. SNs refer to the perceived social pressure to perform or not to perform the behaviour. This relates to one’s intuition about others’ exertion of influence. This study justified that, based on TPB, social pressure’be it from society, peers, or government’will have a positive influence on an individual’s intention to adopt tree planting. Similarly, respondents also believed that their PBC (controllability and self-efficacy) to adopt tree planting significantly influences their attitude (H4) (path coefficient = 0.138). As expected, H4 received strong support. PBC involves people’s beliefs that they have control over the behaviour; performance or non-performance of the behaviour is up to them [72]. Several studies support the direct effect of PBC on intended and/or actual usage [73,74].
In H5, this study posited that farmers’ intention toward tree planting positively influences their behaviour to adopt on-farm tree planting. The model strongly supported this hypothesis. The results were not surprising because intention is proposed to influence behaviour. This theoretical prediction has received considerable empirical support in a variety of settings [75,76]. The intention is an overall evaluation of an individual’s perception of tree planting adoption. Intention is the cognitive representation of a person’s readiness to perform a given behaviour, and it is taken to be the immediate antecedent of behaviour. Therefore, following the TPB, a positive intention undoubtedly affects the individual’s behaviour to engage tree planting activities.
Therefore, the application of TPB offers a theoretical base for the consideration of behavioural attributes in tree planting adoption. Relating these three variables (attitude, subjective norms and perceived behavioural control) to tree planting, a farmer’s behavioural intention is argued to be stimulated by his attitude, subjective norm and perceived behavioural control to getting information, giving information and ultimately using the information in a manner which enhances on-farm tree planting processes in a region and country in general. The tree planting outcomes tend to be incremental (at the individual level) and transformative (at the community level). By incremental, it is referred to changes in farmer’s actual behaviours toward the use of extension practices but leaving the underlying structures or institutions intact, whereas transformative change implies a paradigm shift or a tree planting evolution in a given community. According to [77] incremental changes lead to stable transformative community development.
The findings of the survey were reinforced by the outcomes of the focus group discussions, which besides noting the view that on-farm tree planting and tree management are mostly a task for husbands, the focus group discussions revealed that women still participated in the implementation of tree planting, and there were some gender-specific roles for women, which is in agreement with previous studies [78, 79].
2. Conclusion
Continuing degradation of existing forest cover driven by rapid population growth and anthropogenic activities are serious threats to the sustainability of forestry in Tabora region. Farm and community land forestry uptake has been identified as a feasible solution. Given this scenario, results of this study have shown that farmers’ intention and behaviour toward conserving ecological achievements have been explained well by TPB. The farmers’ behaviour was significantly positively influenced by their intention toward conserving ecological achievements, and their intention significantly predicted their attitude (positive or negative value of performance), followed by the subjective norm (social pressure in engaging behaviour), and least by perceived behavioural control (perceptions of their ability). The farmers’ degree of support for agroforestry uptake and its recognition of environmental effects is the main factor that most influenced the farmers’ attitude.
Guided by these findings and in response to the demonstrated need for sustainable agroforestry in Tanzanian villages, this study has adequately addressed its key objective of testing the explanatory ability of the TPB on farmers’ intention to adopt on-farm tree planting behaviour and has also illuminated the factual evidence gathered from them. The application of this theory in two districts of Tabora region provides an understanding that farmers’ willingness to grow trees on their farms is a function of their attitudes towards the advantages and disadvantages of growing trees, their perception of the opinions of salient referents and factors that encourage and discourage farm level tree planting. These findings can assist in developing tailored forestry programmes, to increase attitudes and foster behavioural change, in order to speed up agroforestry in the region. Farm forestry programmes are likelt to succeed if they acknowledge and address the factors which form the basis for farmers’ reasons for planting or not planting trees. This approach can successfully engage farmers to support the sustainability of the ecology and environment against the uncontrolled agricultural expansion and demand for rural energy fuelled by population growth in the region.