Abstract:
Most invasive alien species reengineer the host ecosystem by altering its structure and functioning so that some new ecosystem services are added and, at the same time, some existing ecosystem services are lost. Prosopis, a woody invasive tree, was intentionally introduced in dry lands of east Africa for its environmental and economic benefits. However, some 40 years later, it escaped from plantations and has invaded significant. This study investigates impacts of Prosopis on the rural livelihoods and environment in drylands of east Africa. The analyses were based on cross-sectional survey data collected in mid 2016 from 250 and 253 households from the heavily invaded Afar National Regional State in Ethiopia and Baringo County in Kenya, respectively. Results from generalized propensity score method analysis indicated that there exists non-linear causal relationship between Prosopis invasion dose and household per capita consumption expenditure. The effect was found to be initially positive but turns to be negative after an optimum invasion dose. Using choice experiment method, the economic values of dry land ecosystem services affected by Prosopis were estimated. A random parameters logit model was employed for analyzing households’ preferences for the affected ecosystem services. It was found that households from both regions are willing to pay for its management primarily driven by concern for the loss of biodiversity and water. Willingness-to-pay was on average higher in Afar (USD 50.42/year) than in Baringo (USD 37.74/year). The results indicate that the costs incurred by the invasion outweigh its benefits in both Afar and Baringo. Triangulation of ground-truths and local perceptions about the effects of Prosopis on biodiversity and three other ecosystem services was done. Though mixed in case of Baringo, ecological results from Afar showed that biodiversity loss, water availability, soil stability and soil fertility were positively correlated with Prosopis invasion density. However, in both study areas, though average household perception levels were in agreement with ecological results, significant number of respondents were against the ground-truths. Results from generalized ordered logit model revealed that social participation, education level and extension service were found to be the significant factors determining local households’ perception levels about the effects of Prosopis invasion on groundwater availability. Similarly, households’ livelihood activities including livestock owned, crop production, charcoal production and other income diversification activities were found to significantly determine local perceptions. Further, it was observed that influences by some of these factors vary between the countries. These findings suggest that improving evidence-based awareness creation, providing pertinent information, including monetary values, on both positive and negative effects of Prosopis invasion on ecosystem services should precede the design and implementation of management options. The results further suggest that in making such awareness creation, local communities’ major livelihood activities should be taken into account, which may increase households’ understanding about the benefits and adverse effects of Prosopis. xxi Finally, the results suggest integrated management option as an effective approach. That is, to maximize the benefits of Prosopis and minimize its adverse effects on the livelihoods of the pastoral and agro-pastoral communities, diverse management strategies that take into account not only the density of invasion, but also the patterns of drylands economy should be implemented. Following this approach, community specific management options should be designed and implemented so that public support and commitment make Prosopis management options both effective and sustainable. Keywords: Prosopis, rural livelihood, ecosystem
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