On the use of contingent valuation method to assess factors affecting the contribution of local people for the management of water hyacinth in Lake Tana, northwestern Ethiopia

The colonization of freshwater lakes by invasive alien species is increasingly alarming primarily owing to nutrient loads from the watersheds. For the sustainable management of invasive weeds, preventive methods, such as watershed management and sustainable agricultural practices, are recommended. Watershed protection activities by the upstream local community are believed to be effective measures to reduce nutrient loading to the receiving water bodies and hence help prevent the spread of water hyacinth. However, their willingness and potential contributions determine the effectiveness of watershed management activities. The objective of this study is, therefore, to evaluate the preferences and contributions (willingness to pay and willingness to contribute labor) of the local community for the management of water hyacinth in Lake Tana (Ethiopia). A contingent valuation method for a hypothetical market "prevention of water hyacinth infestation of Lake Tana through watershed management program" was used to collect data from 560 randomly selected households. A multivariable interval regression model was used to identify factors affecting the contribution of local people. The mean yearly willingness to pay and to contribute labor of the respondents was 435.4 Ethiopian Birr (US$ 10) and 22.4 man-days, respectively. The place of residence (rural/urban), educational level, private farm plot area, annual income, and water hyacinth-related conference participation significantly influenced the willingness to pay. Similarly, the willingness to contribute labor was strongly associated with place of residence, location, educational level, and household family size. The economic value derived from this study reflects community preferences, which could be an input for informed and evidence-based decision-making regarding the prevention of weed expansion and sustainable use of ecosystem services. Therefore, local, regional, and national authorities are advised to mobilize the local community to contribute labor and/or money so as to halt the expansion of the weed.