International Choice Modelling Conference, International Choice Modelling Conference 2017

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The Economic Value of the Tana Delta Mangrove Ecosystem in Kenya
Philip Otieno, Richard Mulwa, Pieter van Beukering, Wouter Botzen, Nicholas Ogugeh

Last modified: 28 March 2017


This study applies a choice experiment to estimate the economic value of the mangrove ecosystem goods and services in the Tana River delta in Kenya. In Kenya, mangroves are concentrated on the northern coast around the Lamu archipelago and the permanent Tana/Sabaki River estuaries, with smaller wetlands in the mouths of semi-perennial and seasonal coastal rivers on the South Coast. The Tana Delta mangroves cover a total of 2350ha. Mangroves provide a host of ecosystem goods and services, such as nursery and spawning ground for fish which benefit fishing, shoreline and storm and flood protection, carbon sequestration, ground water recharge, tourism and recreation, herbal medicines, honey, timber/poles, and fuel wood, among others.


However, mangroves face a continued threat to their existence from conversion into aquaculture, over harvesting, pollution, and upstream developments that threaten the availability of freshwater flooding. These negative impacts on mangroves are driven by decisions which fail to acknowledge the economic values of the goods and services that mangroves provide. Out of a total population of 4220 households in the Tana delta in Kenya, 405 participated in a face-to-face stated preference survey that included a choice experiment. This experiment was designed to value the following attributes of mangrove preservation: shoreline protection, flood control, tourism and recreation, nursery and breeding ground for fish, and volunteering time to preserve mangroves. Volunteer time was chosen as payment vehicle because of the high poverty levels among the study population. The survey was pre-tested and its design was informed by focus group discussions.


A multinomial logit model finds that all coefficients of the attributes are statistically significant at the 1% level. As expected, the utility of the environmental protection alternatives is positively related to the nursery of fish and the number of tourists, while this utility is negatively related to shoreline erosion and the flood probability. An interaction variable of volunteer time with membership of an existing volunteering organization that preserves mangroves shows that volunteer time has opposite effects for members and nonmembers. In particular, members prefer environmental policy options that require more volunteer time, while non-members prefer to spend less volunteer time on environmental protection. Estimated marginal effects show that especially the nursery of fish and flood probability attributes have a large influence on respondents’ choices. A model that examines individual heterogeneity in preferences for mangrove conservation finds a distance decay effect, in that individuals who live further away from the mangroves have lower values for preservation.


Individual maximum willingness-to-pay (WTP) levels for non-members per attribute are estimated in terms of volunteering time per month or monthly opportunity costs. The results show that individuals are on average willing to spend approximately 5 hours monthly for gains in fish nursery per 1000 additional ton of fish, 2 hours per month for attracting 100 additional visitors, 1 hour per month to prevent a meter of shoreline protection and 2 hours per month to prevent each 0.1 increase in flood probability. The figures about willingness to put in volunteer time are translated to opportunity costs amounts by multiplying hourly time with the local average hourly wage of Ksh. 50 (Ksh. 400 per day). This results in monetary WTP values of Ksh. 247 per tonne of fish, Ksh.83 per 100 tourists, Ksh. 43 per meter of prevented shoreline erosion, and Kshs 121 to prevent an increase in the flood probability of 0.1.


Both the market price and choice experiment methods were used to determine the direct use and indirect-use values of the mangroves, respectively. From our results, on average, each hectare contributes US$ 343 of direct use values, and US$ 1838 indirect use values per year. The total economic value of the mangrove is therefore estimated at US$ 2181 per hectare per year. Note that non-use values were not estimated, so the estimated value forms the lower boundary of the total economic value of the Tana delta mangroves. The average total economic value is within the range of estimates in other mangrove ecosystems elsewhere in the world.


This study demostrates that mangroves have substantial economic benefits, both directly and indirectly. Although indirect values cannot be easily appreciated and included in economic decision making, estimates show that they are much higher than the direct use values. In order to harness the economic benefits of the mangroves, it is imperative that an adequate ecological balance is maintained so that resource inputs neccesary for their good health are not disturbed. A number of intereventions can be put in place to ensure sustained provision of these ecosystem services. These include limiting sea wall construction and enhancing mangrove restauration, creating awareness of the ecosystem services provided by mangroves to limit overxploitation, diverting fishing activities away from mangrove spawning areas and towards deep sea fishing, and enhancing the ability of the communities to capture the economic benefits of mangrove preservation through eco-tourism and beekeeping.

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