VALUES AND SERVICES OF A PROTECTED RIVERINE ESTUARY IN EAST AFRICA: THE WAMI RIVER AND SAADANI NATIONAL PARK

The dialogue pertaining to the management of riverine and coastal ecosystems has evolved over the past decade to consider ecosystem goods and services due to their ability to link ecosystem structure and function to human well-being. Ecosystem services are “a wide range of conditions and processes through which natural ecosystems, and the species that are part of them, help sustain and fulfill human life” (Daily et al. 1997 p.2). Ecosystem goods emerge from ecosystem services and are defined as “organisms and their parts and products that grow in the wild and ... are used directly for human benefits” (Daily et al. 1997 p.4). Protected areas, such as national parks, and environmental flow regimes that identify critical aspects of river flow, are increasingly being utilized as management measures to enhance resiliency, protect biodiversity, and preserve the delivery of ecosystem goods and services. Recently it been proposed that aquatic ecosystem goods and services can serve as a common currency to account for the benefits and losses associated with altered flow regimes and define the risks in a transparent manner since they provide immense value to all stakeholders (Arthington 2012). Adopting this idea, my dissertation research comprises three studies focused on the ecosystem goods and services related to the protected portion of the Wami River and Estuary encompassed within Saadani National Park (SANAPA), Tanzania. The first study investigates the use and perception by different groups of downstream stakeholders of the value of ecosystem goods and services. The second study examines the effect of SANAPA on the tradeoff between two specific ecosystem services and whether the local surrounding communities fell into a poverty trap as a result of the restrictive measures put in place when the park was created. The third study assesses how proposed water withdrawals for a large scale irrigation project located just upstream of the park’s boundary would alter the freshwater inflow regime and potentially impact the delivery of ecosystem goods and services to SANAPA and the neighboring local communities. The need for enhanced understanding of how different stakeholders perceive and depend upon an array of ecosystem goods and services is a critical research priority. In our first study, we employ a mixed methods approach comprised of focus groups and face-to face surveys to examine the specific ecosystem goods utilized by residents and compare and contrast the perceived value of 30 ecosystem services held by upstream residents, downstream residents, tourism officials, and conservation organizations. Our key finding is that a good deal of consensus exists among these groups in regards to which ecosystem services are deemed most and least valuable. Each group places a high value on the provision of domestic water, habitat for wild plants and animals, tourism, and erosion control, and a relatively low value on the prevention of saltwater intrusion, refuge from predators, spiritual fulfillment, non-recreational hunting, and the provision of traditional medications and inorganic materials for construction. Differences emerge, however, between the groups in the value assigned to the conservation of riverine and estuarine fauna, intrinsic value, and the provision of raw materials for building and handicrafts. The fact that residents assigned a higher priority to raw materials and a lower priority to the intrinsic value and conservation of riverine and estuarine fauna than the tourism and conservation officials suggests that they are very reliant upon the resources of the Wami River and Estuary for their sustenance and income. The findings from our first study fall in line with the larger pattern observed around the world, namely, that many coastal communities in developing countries, especially the rural poor, rely heavily upon natural resources for their subsistence and livelihoods. Their access to these resources, however, often changes when protected areas are established. The shortand long-term gains and losses to local residents associated with protected areas remain largely unexplored, especially empirically. In our second study, we integrate remote sensing data of mangrove cover with georeferenced household survey data in an econometric framework to assess the environmental and economic impacts of enhanced mangrove protection efforts undertaken to preserve biodiversity in SANAPA on the neighboring local communities. Specifically, we examine the effect of strengthened enforcement of the prohibition of mangrove harvesting on the tradeoff between two specific ecosystem services (i.e., the short-term benefits from cutting mangroves and the long-term benefits from harvesting the fish and shrimp that thrive if mangroves are not cut), and whether households fell into a poverty trap as a result. Our findings suggest that many households experienced an immediate loss in the consumption of mangrove firewood with the loss most prevalent in richer households. However, all wealth classes appear to benefit from longterm sustainability gains in shrimping and fishing which result from mangrove protection. Overall, the households that have stopped using mangroves for firewood can be considered the “losers” from establishment of SANAPA, while those who started fishing/shrimping (or making more revenue out of it) are the “winners.” Our data suggest that there are more “winners” than “losers” with the proportion of households that newly engaged in mangrove-related income activities after SANAPA outweighing the proportion of households that no longer use mangroves for their firewood. The creation of SANAPA shifted the future trajectory of the area from one in which mangroves were experiencing uncontrolled cutting to one in which mangrove conservation is providing gains in income for the local villages due to the preservation of nursery habitat and biodiversity. While the results of our second study are encouraging, the health of the mangroves, existence of the mangrove reliant fish and shrimp species, and continued delivery of the other ecosystem goods and services valued by the stakeholders in our first study, are dependent upon sustained freshwater flows into the lower reaches of the Wami River and Estuary. Upstream anthropogenic activities can alter the magnitude, frequency, duration, timing and quality of freshwater inflows. These alterations to the natural flow regime can cause abiotic and biotic changes within the downstream riverine, estuarine, and coastal ecosystems affecting the availability of the ecosystem goods and services, and in turn, the overall well-being of the stakeholders reliant upon them. In our third study, we examine the potential effects of water withdrawal (i.e., abstraction) from a proposed 10,500 hectare irrigated biofuel project on the Wami River on the delivery of ecosystem goods and services to SANAPA and the neighboring local communities. We utilize daily flow data collected from 1954 to 1978 to derive a number of low flow and extreme low flow parameters for flow durations ranging from 1 to 90 days to characterize the historic and post-irrigation freshwater flow regime of the Wami River. Our findings demonstrate that the proposed withdrawals during the dry season would dramatically alter the flow regime of the lower Wami River and create conditions unlike any observed over the 24 year period of flow records analyzed. Under the abstraction scenario, there is a 10-fold increase in the occurrence of low flow values observed historically. Moreover, the incidences of zero flow days over the 24 year period of record rise from 15 to 300, creating extended periods of noflow conditions that would completely dry out lower portions of the Wami River. These changes would have profound effects on the habitats, wildlife, fisheries, and human values and functions that constitute Saadani National Park. Therefore, it is essential that large scale water withdrawals must be approached with caution in perennial, freeflowing rivers draining arid watersheds of eastern Africa to sustain the critical riverine and estuarine linked ecosystem goods and services of downstream protected areas.

7. Did the tradeoff between two provisioning ecosystem services from mangrove forests (i.e., the short-run benefits from cutting the above ground biomass of mangroves for fuelwood and charcoal production versus the long-run benefits from harvesting the fish and shrimp that thrive in the prop roots of uncut mangroves) result in a poverty trap for the local communities surrounding SANAPA?
8. What are the characteristics of the historic/pre-altered flow regime that have supported the ecosystem goods and services currently provided by the Wami River and its estuary?
9. How will proposed upstream irrigation withdrawals for biofuel production change the Wami River's flow regime? xiii 10. How might the altered flow regime impact the ecosystem goods and ecosystem services utilized and valued by the different groups of downstream stakeholders?
The first manuscript addresses research questions 1-5, and will be submitted to the journal Ecosystem Services.
The second manuscript addresses research questions 6 and 7, and was published in 2011 in PNAS (citation is below).
McNally, CG, Uchida E, Gold AJ (2011) The Effect of a Protected Area on the Tradeoffs Between Short-run and Long-run Benefits from Mangrove Ecosystems. Proceedings of the National Academy of Sciences 108 (34):13945-13950.

N.B. The econometric techniques used to explore the causal linkages between mangrove protection and poverty in our PNAS manuscript is the work of Dr. Emi Uchida and is not a component of my own dissertation research.
The third manuscript addresses research questions 8-10, and will be submitted to the journal River Research and Applications.
xvii LIST OF TABLES  Table 2.S1 Summaries of research articles pertinent to our study……………………………….87 Table 2.S2 Perceptions of the effect of SANAPA on livelihood, 2010……………………………89  Table 3.3 Monthly mean and median flows: historic flows versus projected flows following proposed biofuel irrigation abstractions…………………………………………………….126 Table 3.4 Statistical summaries for cumulative low flow indices: historic flows versus projected flows following proposed biofuel irrigation abstractions……………………………127 Table 3 Ecosystem services are "a wide range of conditions and processes through which natural ecosystems, and the species that are part of them, help sustain and fulfill human life" (Daily et al. 1997 p.2). The Millennium Ecosystem Assessment classifies ecosystem services into four groups: regulating services (e.g., water purification/waste treatment, flood and drought mitigation); supporting services (e.g., habitat for terrestrial, riverine and estuarine flora and fauna, nursery function, nutrient cycling); provisioning services (e.g., food, fiber, fuel); and cultural services (e.g., recreation, tourism, education, aesthetics, and spiritual significance). Ecosystem goods emerge from the ecosystem provisioning services and are defined as "organisms and their parts and products that grow in the wild and … are used directly for human benefits" (Daily et al. 1997 p.4).
Examples of estuarine and riverine ecosystem goods include fish, vegetation for food and medicinal purposes, and timber for construction and fuel.
Empirical studies conducted to date have employed a number of different approaches to examine stakeholder perceptions of ecosystem services including i) recognition and identification; ii) rating; and iii) ranking perceived levels of importance.
The first type of approach asks stakeholders to either answer "yes", "no", or "do not know" in response to whether a predefined set of ecosystem services are important (e.g., Sodhi et al. 2010), or to self-identify ecosystem services they deem as important (e.g., Hartter 2010). The second approach asks stakeholders to rate the importance of pre-defined ecosystem services using a Likert scale (i.e., 1 = low importance, 2 = important, and 3 = very important) (e.g., , Warren-Rhodes 2011).
The third approach asks stakeholders to either identify the three most important services overall (e.g., Iftekhar and Takama 2008) or to distribute a fixed number of counters (e.g., marbles or pebbles) to rank numerous ecosystem services in relation to one another (e.g., Agbenyega  Africa), and rely heavily upon natural resources for their subsistence and livelihoods. 1 Exceptional resource values are defined as the "biophysical features of a national park that are assessed as being especially important to maintaining the unique ecological character and functions of the park and that provide outstanding social, economic and aesthetic benefits to local, national, and international stakeholders" (SANAPA 2009, p. 8).
Despite this dependence, the majority of biodiversity conservation efforts undertaken in Tanzania within the past fifty years have adopted a top-down approach with limited attention to local residents' needs and priorities (Mangora 2011, Sigalla 2013). Information is warranted on the perspectives and needs of poorer local residents since their dependence on goods and services from the natural environment may foster priorities that differ from those of international conservation organizations, and tourism operators catering to wealthy international tourists (Roe and Walpole 2010). The values of these different stakeholder groups can emerge from historical context as well as past, present, and future needs and interests (Dick et al. 2011). Here we describe a study conducted in the Wami River estuary river/estuarine complex of East Africa that is dominated by a protected national park and surrounded by villages with high levels of poverty.
We compare and contrast the use and perceptions of four different stakeholder groups (i.e., upstream residents living adjacent to the Wami River, downstream residents living adjacent to the Wami River Estuary and coast, tourism officials, and conservation organizations) regarding the value of ecosystem goods and services provided by the Wami River and its estuary, and determine what they perceive as the main threats to this system. This study seeks to address key information gaps identified by Sarmett and Anderson (2008) that can be useful for future management efforts within the Wami River Estuary.
Specifically, we examine the following research questions:  Figure 1).

Methods
Our study employed a mixed methods approach comprised of face-to-face surveys and focus groups to gather extensive qualitative and quantitative data on the stakeholders use and perceived value of ecosystem goods and services, as well as their main concerns regarding future conditions of the Wami River and its estuary. The survey instrument included separate sections for ecosystem goods, ecosystem services, and stakeholder concerns while the focus group questions focused specifically on the types of ecosystem goods utilized by the local communities. The appropriateness and clarity of the focus group discussion and survey questions were evaluated in pilot testing with a community in Tanzania before commencing data collection.  (Cohen 1988).
In the main concerns section of the survey, each respondent was asked, "What do you see as possible problems for the Wami River and Wami River Estuary?" The responses were classified into different groups, and the overall percentages of each stakeholder group identifying the specific categories were calculated. Chi-Square tests for equality of proportions were employed to examine whether the perceived problems differed across the stakeholder groups and Cramer's V were calculated to measure effect size. Values < 0.3 signify a small effect, ≥ 0.3 to <0.5 signify a medium effect, and ≥ 0.5 signify a large effect (Gravetter and Wallnau 2004).
The ecosystem goods section, which was only given to the local residents, was designed to augment the information gathered in the focus group discussions, and included questions to gather information on the most common activities conducted at the Wami River and Estuary, the sources of water for drinking, cooking, and bathing as well as the quantity of water collected per day. Each respondent was asked whether they visit the Wami River and Estuary, and if so, how often and for what purposes. The resulting data were analyzed with descriptive statistics.
The focus group discussions were convened for the local residents within upstream and downstream communities to gather specific information on the fish and crustacean species captured in the river and adjacent coastal waters for food and livelihoods as well as the specific mangrove and riparian species utilized for medicinal purposes, fuelwood, and building materials. Once the species lists were compiled, the focus group participants were asked to collectively rate each species overall importance on a scale of 1 (not very important) to 4 (very important).

Stakeholders Perceptions of the Relative Importance of each Category of Ecosystem Services
The relative importance assigned to each of the ecosystem service categories by the stakeholder groups ranged from 17 to 37% ( Figure 2). Looking across groups, the median value assigned to the entire set of provisioning services by the upstream and downstream residents was significantly higher than the median values assigned by the tourism officials (p=0.008, d=0.32 and p=0.003, d=0.35, respectively) and conservation employees (p=0.017, d=0.29 and p=0.011 d=0.30, respectively) ( Table 2). The perceived level of importance for the supporting services was similar among the four stakeholder groups while the upstream residents valued the regulating services significantly lower than the tourism officials (p=0.016, d=0.29) and conservation employees (p=0.023, d=0.28) (Table 2). Similarly, the upstream residents also valued the cultural services significantly lower than the tourism officials (p=0.008, d=0.32) and conservation employees (p=0.011, d=0.31) (  Table 2).

Regulating Services
All four of the stakeholder groups surveyed in this study perceived erosion control as a valuable regulatory ecosystem service while the prevention of saltwater intrusion was not valued highly by any group (Table 3). In addition to erosion control, the residents placed high value on the delivery of water and sediments to maintain nursery habitats and water purification. Similarly, tourism operators placed high value on water purification. Overall, the conservation employees distributed their counters more evenly among the regulatory services than the other stakeholder groups. The perceived importance of the Wami River and Estuary in maintaining nursery habitats was significantly higher for the residents and conservation employees than the tourism operators (p<0.0001, d=0.43 and p=0.003, d=0.4, respectively) ( Table 3).

Supporting Services
At the group level, all four of the stakeholder groups surveyed perceived the existence of healthy ecosystems/habitat for wild plants and animals as the most valuable supporting service followed by plant and terrestrial animal conservation ( Table   4). None of the stakeholder groups perceived refugium function as a particularly valuable service, and as seen within the regulating services, the tourism officials did not place a high value on nursery habitat. Although all of the stakeholder groups surveyed in this study identified habitat for wild plants and animals as the most valuable supporting service, the residents' median value was significantly higher than the conservation employees (p=0.011, d=0.24) and tourism operators (p<0.0001, d=0.36).
The perceived importance of the Wami River and Estuary in riverine/estuarine animal conservation was significantly higher for the tourism and conservation employees than the residents (p<0.0001, d=0.39 and p=0.002, d=0.29, respectively).

Cultural Services
All four of the stakeholder groups surveyed in this study perceived tourism as a valuable cultural ecosystem service while spiritual fulfillment in connection with the Wami River and Estuary was not perceived as important by any of them ( Table 5). The tourism officials placed the highest value on tourism while the conservation employees placed the highest value on the intrinsic value of biodiversity conservation. In both cases, the median values were 50% higher than the expected value. In addition to tourism, the residents placed high value on science and education as well as a significantly higher value on aesthetics than both the tourism officials (p<0.001, d=0. 36) and conservation employees (p=0.015, d=0.23). The tourism officials perceived aesthetics as significantly less important than the conservation employees (p=0.043, d=0.36), but placed a significantly higher value on recreation than the conservation employees (p=0.008, d=0.41) and residents (p=0.001, d=0.31) ( Table 5).

Provisioning Services
At the group level, all four of the stakeholder groups surveyed perceived domestic water as a very valuable provisioning ecosystem service as exemplified by median values twice as high as the expected value (Table 6). However, there were significant differences in the values placed on specific types of provisioning services based upon the residents' proximity to the freshwater and estuarine ecosystems within the Wami River and Estuary. The upstream residents placed a significantly higher value on flood recession agriculture than the downstream residents (p=0.001, d=0.38) while the downstream residents placed a significantly higher value on fish and shrimp for subsistence and commercial fisheries than the upstream residents (p=0.015, d=0.26).
While all stakeholder groups perceived traditional medicinal plants and inorganic raw materials as relatively unimportant, the downstream residents placed a significantly lower value on vegetable and fruit production than the other stakeholder groups (p<0.05, d ranged from 0.29 to 0.37). Furthermore, they also placed a significantly higher value on organic raw materials for building and handicrafts than the tourism officials (p=0.014, d=0.29) and conservation employees (p=0.006, d=0.32).

Ecosystem Goods
Given the significantly high value assigned to the provisioning ecosystem services by the upstream and downstream residents, we decided to further examine the reasons the local residents visit the Wami River and Estuary. There was substantial variability between subvillages in the extent of water collection for drinking and cooking that did not relate to their upstream or downstream locations, but appear to link to availability of alternative water sources. Several sub-villages (Matipwili, an upstream village, and

Main Concerns
Seventy-three percent of upstream and downstream residents identified declining fish populations as a prime concern regarding the future conditions of the Wami River and its estuary ( Table 7). Fifty percent or more of the downstream residents also identified increasing salinity levels, declining shrimp populations, and the loss of mangroves as key concerns. The second most common concern voiced by the upstream residents was increasing human population, which was the most frequent concern identified by the conservation employees. Forty percent of the conservation employees also identified declining fish populations, increasing salinity levels, and the loss of mangroves as primary concerns. Additional water abstractions from the Wami River for upstream agriculture as well as proposed irrigation withdrawals for a biofuel project just upstream of the park boundary were causes of concern for at least one-third of the conservation employees and 29% of the upstream residents. In comparison to the other stakeholder groups, many of the tourism officials noted during the surveys that it was very difficult to predict foreseeable problems since they only visit the Wami River and Estuary on occasion.

Synergies and Tensions among the Stakeholder Groups
As expected, the upstream and downstream residents placed a high priority on the provisioning services tightly linked to their sustenance and main sources of income.
Likewise, the tourism officials highly valued tourism while the conservation employees provisioning services suggests that there is common ground among the groups that future management efforts within the Wami River and Estuary can build upon.
In addition to identifying potential areas of mutual interest, the results of our survey also highlighted possible tensions among the stakeholder groups that managers need to bear in mind and account for in future management efforts. While both the upstream and downstream residents concurred with conservation and tourism stakeholders on the importance of habitat, they placed a significantly lower value on intrinsic values (i.e., conserving an element of biodiversity for its own sake without the intention of using it) and conservation of riverine and estuarine fauna. Additionally, the downstream residents placed a significantly higher value on the provision of raw materials for building and handicrafts than the other groups. The results of our focus group discussions highlighted that they rely on a number of mangrove species for these materials (i.e., A. marina, B. gymnorrhiza, C. tagal, R. mucronata, and X.granatum).
However, if not managed properly, overharvesting could lead to tradeoffs with many of the other highly valued ecosystem services associated with mangroves (e.g., erosion control, coastal protection, habitat provision, aesthetics, tourism etc.).

The Prioritization of Ecosystem Services by Each Stakeholder Group
The high and low level of importance assigned by local residents to the categories      Si gni fi ca nt a t <0.05. The l etters a , b a nd c a re us ed to connote di fferences wi thi n s ta kehol der groups (l ooki ng down a col umn) a nd l etters y a nd z a re us ed to connote di fferences between s ta kehol der groups (l ooki ng a cros s a col umn).
The values in the table are median (interquartile range).

Regulation Ecosystem Services
Kruskal-Wallis and Mann-Whitney U tests were conducted. Statistical differences between group values with rows that have a different letter are significantly different based on **: p<0.01. higher and lower, respectively, than the expected value.

Habitat Ecosystem Services
Kruskal-Wallis and Mann-Whitney U tests were conducted. Statistical differences between group values with rows that have a different letter are significantly different based on *: p<0.05, **: p<0.01.
Science and education 5 a* (3) Kruskal-Wallis and Mann-Whitney U tests were conducted. Statistical differences between group values with rows that have a different letter are significantly different based on *: p<0.05, **: p<0.01 and *** p<0.001.
The values in the table are median (interquartile range). Those in bold and italics denote values 50% higher and lower, respectively, than the expected value.
Organic raw materials for building and handicrafts Inorganic raw materials for construction

Introduction
Mangrove forests comprise only 0.12% of the world's total land area, but are highly productive ecosystems that underpin a major portion of the world's fisheries (1,2). Mangroves thrive where many other species cannot survive, and are important habitat for associated flora and aquatic and terrestrial fauna (1,(3)(4)(5), with more than 1,500 faunal species inhabiting mangroves in the Indo-Malaysian region (3,4).
Many coastal communities in developing countries, especially the rural poor, rely upon extraction of mangrove forests for their subsistence and livelihoods (6-7).
Overexploitation for fuelwood, charcoal, and timber production has degraded more than one quarter of the world's mangrove habitats (8). Penaeid shrimp production decreases precipitously as the remaining mangrove area is reduced (11).
The rapid destruction of mangrove forests has spawned a host of protected areas across the world. However, given the reliance of many local communities on mangrove forests for fuelwood, charcoal, and other uses from harvested mangroves, protection efforts that sustain the long-term viability of these ecosystems -including their value for fisheries -could pose an immediate threat to livelihoods of the rural poor. Without some mechanism to compensate the affected households, protected areas can place them in a poverty trap, i.e., a mechanism that causes poverty to persist (12). However, if protected areas can enhance long-run livelihood opportunities for the poor, they can potentially be a win-win solution for conservation and poverty alleviation. This question underlies the literature in integrated conservation and development projects and their variants, which are recent efforts to conserve biodiversity and alleviate poverty together (13)(14)(15). However, there has been little empirical evidence of successful delivery of both goals (16).
This article demonstrates that improvements in mangrove ecosystems that result from a protected area have resulted in tangible improvements in incomes for the poor. The impact of protected areas on the natural resources and the local communities' livelihood, and the variation of the impact among households in different wealth groups remain largely unexplored (17)(18)(19). Protected areas often create tradeoffs among multiple ecosystem services, making it challenging to quantify and assess the linkage between the human and natural systems. Previous studies do not show strong linkages between changes in natural resources and use patterns at the household level.
In the context of mangrove conservation, although previous studies linked variations in mangrove areas to potential benefits from fisheries (e.g., refs. 20-23), they do not observe actual changes in mangroves and their effects on tangible benefits in the form of income or consumption. Moreover, most studies do not clearly identify the causal link between protected areas and poverty because they fail to use direct measures of well-being and fail to control for potential confounding effects of baseline characteristics (17,18). Protected areas in developing countries are often established in remote areas with high poverty rates and few alternative livelihood strategies (24). To identify whether protected areas create tradeoffs among different benefits from mangrove forests, the appropriate comparison would be between households living near protected areas and households with similar characteristics and trends that are not affected by protected areas (18).
The overall goal of this study is to assess the environmental and economic impacts of a major mangrove protection effort undertaken to preserve biodiversity in Saadani National Park (SANAPA) in Tanzania. This region has mangrove forests, which sustain a rich biodiversity, but the local communities suffer from persisting poverty. Finally, there are opportunities for new non-agricultural employment (largely with SANAPA). The first two impose negative effects on villagers and the last two generate positive gains, at least for those who fish or shrimp or attain jobs with the park service.
To meet these objectives, we coupled geospatial and georeferenced household survey data to examine local changes in mangrove cover and socioeconomic impacts of SANAPA. In an effort to overcome some of the previous limitations in protected areas and poverty studies, we assessed the components of income that are directly linked to ecosystem services from mangrove forests. We also used econometric techniques to explore causal linkages between mangrove protection and poverty. In addition, we extended the model to understand how the establishment of the protected area affected households from the three wealth segments (poorer, middle, richer), which were defined based on the total value per capita of productive and consumable asset levels in 2004.  (Fig. 1a) (25,26). It protects a range of different habitats, including coastal forests, mangroves, and coral reefs, and encompasses the Wami River Estuary, a critical habitat for many species of fish, shrimp, and birds (25).

Site Description and Mangrove Protection Efforts
The Estuary provides extensive lengths of mangrove-lined habitat edge, where juvenile shrimp have access to the mangroves. This type of configuration has been shown to be a more important indicator of shrimp densities, as there is a direct relationship between length of mangrove-lined habitat edge and density of juvenile shrimp (27). Also, the abundant and diverse bird population associated with these mangrove forests are a draw for ecotourism.
Before the establishment of the park, very high levels of mangrove cutting for charcoal production, firewood, and building materials threatened both the local artisanal fisheries and the biodiversity of the area (7,25,26). This rapid degradation of mangrove forests was in part caused by weak property rights and enforcement (28).
Between 1995 and 2005, the total mangrove area within the current park boundaries decreased by 27% ( Table 1). The creation of SANAPA prohibited the consumptive use of all mangrove resources within the park's boundaries (26). residents, it appears that enforcement of the ban on mangrove fuelwood harvest occurs beyond park boundaries; many villagers are now afraid to harvest mangroves from areas within and surrounding SANAPA. In addition to enhanced enforcement, some collaborative community mangrove forest management initiatives outside of SANAPA's boundaries, but within our study area, commenced in the mid-1990s (29).
SANAPA is surrounded by rural villages with persisting high poverty rates (7,30).
In Bagamoyo district, 40% of the village inhabitants lived below the poverty line in 2000.
The region lacks basic needs (89% do not have access to a piped or protected water source and 94% do not have electricity) and suffers from one of the highest infant mortality rates in Tanzania. Additionally, there is high population growth [i.e., total population increased on average by more than 2% per year between 1998 and 2009 (7, 31)] and low investment, and most households lack access to credit and insurance markets. The rural poor living in the vicinity of SANAPA largely depend on and earn their livings from natural resources, and their livelihoods are tightly linked to the ecosystem services provided by the mangrove forests. For example, focus groups conducted in our study area revealed that, for many households, shrimping and fishing were the only lucrative income activities, and in some areas, mangroves are still the only fuel source.

Results
Changes in Mangrove Cove. The loss of mangroves within SANAPA slowed considerably following the park's establishment in 2005 ( Fig. 1c and Table 1 Although we have clear evidence that management practices are protecting and enhancing mangrove cover within SANAPA, more site specific data on improvements in biodiversity and the response of dependent fauna within the Wami River Estuary will require concentrated monitoring efforts (SI Published Literature Table S1). The household data show that shrimping and fishing incomes have increased over time ( and, in the case of fishing, increase in consumption per day as well. The differences in the results between mangrove cover within and outside SANAPA may also reflect the greater fisheries productivity expected from mangroves located along the edge of riverine estuaries as occurs with the Wami River Estuary of SANAPA. We acknowledge, however, that, in theory, the same effect may also arise independently of the protected area, e.g., as a result of a price increase or improvements in harvesting technology, for which we cannot control in our analysis because of a lack of data (SI: Materials and Methods).

Changes in Mangrove
The results also reveal that degree of monitoring for enforcement, as proxied by the distance to boat ramp, has had an effect on shrimping income, but not on fishing income. Specifically, the interaction term between change in mangrove area outside SANAPA and distance to boat ramp is negative and significant for changes in shrimping income per capita, meaning that the closer the mangrove area is to the enforcement officers' base, the larger the increase in shrimping income. This finding suggests that there may be some spillover effect of enforcement beyond the park boundaries. This coefficient was negative but insignificant for fishing income.
In addition, we find that, although the new entrants to shrimping and fishing were in the poorest group, the effect of the increase in mangrove area within SANAPA on incomes does not particularly favor the poor ( Overall, the households that have stopped using mangroves for firewood can be considered the "losers" from establishment of SANAPA, whereas those who started fishing/shrimping (or making more revenue out of it) are the "winners." Our data suggest that there are more "winners" than "losers": the proportion of households that newly engaged in mangrove-related income activities after SANAPA outweighs the proportion of households that no longer used mangroves for their firewood. In our sample, the proportion of households that used mangroves for firewood decreased by 5%. In contrast, during the same time period, households that newly engaged in shrimping increased by 7% and those who engaged in fishing increased by 16%.

Mangrove Protection vs. Poverty Trap
The expansion of mangrove protection through the creation of SANAPA and enhanced enforcement led to a markedly different future for the mangrove forest species and the biodiversity within that habitat. It also influenced the welfare of the adjacent communities that have been relying on these forests for their livelihood. The trajectory shifted from one in which the mangroves were experiencing uncontrolled cutting, which was destroying the foundation of a critical ecosystem, to one in which mangrove conservation is providing gains in income for the local communities through the preservation of nursery habitat and biodiversity. Our findings suggest that SANAPA has created a tradeoff between the short-run benefits from cutting mangrove forests and potential long-run benefits from not cutting mangroves -and these tradeoffs appear to differ somewhat by household wealth. Many households have experienced an immediate loss in the consumption of mangrove firewood, with the loss most prevalent in richer households.
The households that have entered the fisheries since 2005 were in the poorest group of our sample, suggesting that they have benefited considerably from protection of mangrove forests. At the same time, all wealth classes appear to benefit from longterm sustainability or gains in shrimping and fishing that result from mangrove protection in the Wami River Estuary. This is in contrast to other studies that found that the impact of protected areas was not uniform across households, or that nonpoor households captured most of the welfare gains (7,17,36).
However, it is not clear whether the continued protection of mangrove cover would avoid a poverty trap in the long run. Only 2% of the households in the poorer group changed to a different source of fuel since 2005, suggesting the need for some support to transition to alternative fuel sources. Another concern is that there exists no formal mechanism for the "winners" of the protected area (i.e., those who enjoy increased fishing opportunities) to compensate the "losers" (i.e., those who lost access to mangroves for firewood and other uses). Without such mechanism, tensions may arise in the future. Furthermore, the sparse data environment for artisanal fisheries in Tanzania precludes us from assessing whether the current rate of harvest is sustainable. Our field work and survey data show that SANAPA already generates a number of new direct and indirect benefits to the local communities. If these benefits grow with the expansion of ecotourism, there is potential for further poverty alleviation (Table S2).
As an example of direct benefits, SANAPA directs a portion of the park fees to local communities for building schools, dispensaries, and mosques. In addition, park personnel assist in supplying drinking water to the communities through the construction of pumps and collection of non-saline river water, and help to transport ill community members to regional hospitals. SANAPA can also provide indirect benefits to the communities through improving roads and cellular phone towers and the creation of temporary and permanent employment opportunities in tourism. Our survey confirmed that these factors were perceived as benefits by the local communities, especially among those who live closer to SANAPA. Together with increases in mangrove related incomes, these benefits may turn SANAPA into a win-win strategy.  (Fig. 1a). We selected an area encompassed within a 5-km radius of each subvillage to reflect the likely travel distance for subvillage fishermen. The continental shelf in this area extends less than 5 km offshore, and most small-scale fishermen do not have access to the technology (e.g., outboard or inboard engines and cooling or freezing facilities) and the capital needed to fish in waters greater than 5 km offshore (7,37).

Geospatial
We next combined the geographic information systems mangrove data with a survey data set obtained from georeferenced households. We administered the survey in April 2010 to evaluate the livelihood impact of SANAPA. The survey instrument was approved by the University of Rhode Island Institutional Review Board on Human Subjects. The household survey used a stratified sampling strategy designed to collect data on a random sample of 150 households in the SANAPA area. From 15 subvillages in the SANAPA area (Fig. 1a), which are of varying distances from the park boundary, 10 households per subvillage were randomly selected. Our sampling frame includes only subvillages that have some access (i.e., by roads or water) to mangroves, some of which are within the park boundaries. By using the survey data, we were able to produce information on mangrove-related income (shrimping and fishing) for both before (in To identify the impact of SANAPA on mangrove-related incomes from fishing and shrimping, we used the variation across households in the changes in mangrove area within SANAPA boundaries. Specifically, we first use the GPS coordinates of the central location of each subvillage to draw a 5-km radius circle around each subvillage (Fig. 1a).
We then calculate the changes in mangrove cover (in km 2 ) in each 5-km-radius circle Moreover, they also could result from unobservable factors that affect both mangroves and mangrove-related income (e.g., a community's ability in managing mangroves) and location-specific factors that affect productivity of mangroves. To evaluate convincingly the impact of the protected area on mangrove-related incomes, we need to control for time effect and unobservable factors to the extent possible. We also had a sample selection issue in which a large proportion of respondents reported zero income for certain income categories. If we did not deal with these issues, the estimates of the impact of establishing SANAPA could have been biased.
Our identification strategy attempted to deal with these issues through several different econometric methods. First, we used data on two periods -before and after the establishment of SANAPA -and applied a method to control for sample selection for panel data (38). Specifically, we used a first-differenced model, which is equivalent to a fixed-effects model with two periods, with inverse Mills ratios (IMRs) for each period (SI

Materials and Methods).
This approach allowed us to control for time trends, timeinvariant unobservable factors, and sample selection. We acknowledge the shortcoming, however, that this approach does not allow us to control for time-varying factors that could affect fishing and shrimping income, such as prices and fish stock.
Second, to address the potential confounding effect of changes in mangrove cover outside the protected area, we controlled for changes in mangrove cover outside SANAPA within 5 km from each subvillage. We expected a smaller coefficient on this variable compared with within-SANAPA mangrove cover for the following two reasons.
First, there is a placement effect, i.e., SANAPA protects the areas that are key shrimp and fish breeding areas. Second, there could be quality differences in mangroves; presumably, mangroves within the park boundaries have better protection and hence are more productive as a habitat. We also created a variable to proxy the degree of enforcement by calculating the distance between each subvillage and the park's boat ramp at which the park enforcement agents periodically reside. We explored whether subvillage proximity to the boat ramp is associated with stronger enforcement. As anecdotal evidence suggests there could be some spillover effect of enforcement to areas outside the park boundaries, we attempted to capture this effect by interacting the distance to the boat ramp and the mangrove area outside the park boundaries. A positive coefficient would indicate that an increase in mangrove area outside the park boundaries is associated with a larger increase in shrimping or fishing income if the subvillage is closer to the boat ramp and is subject to stronger enforcement.
In sum, we estimate the following empirical model: where y it is the outcome variables of interest (i.e., shrimping and fishing income) for individual i in year t; x it is a vector of time-variant observables, including the distance from the boat ramp (measure of enforcement after establishment of SANAPA) and the interaction term between mangrove cover outside the park boundaries and the distance from the boat ramp; α i is an individual fixed effects; λ it is a vector of IMR from a probit model for each year; and ε it is the error term. We report a robust SE that corrects for heteroskedasticity (SI Materials and Methods, Table S3).
In addition, we extended the model to understand how the establishment of the protected area affected households from the three wealth segments (poorer, middle, richer) differently. Specifically, we divided the sample into terciles (i.e., three groups of equal size) based on the value of productive and consumable asset per capita (SI Survey). We then added to Eq. (1) dummy variables for the poorer and middle groups (richer group as the base category) and the interaction terms between the dummy variables and the variables for mangrove areas. Intuitively, coefficients on these variables measure how the impact of increased area in mangroves in SANAPA differs for the two groups relative to the richer group. Descriptive statistics for the variables are available in Table S4.     (Table S1). However, mangrove replanting does not always result in the same level of fish and benthic macrobiota species diversity found in natural cover due to lower accretion rates of fine and organically rich sediments and differences in the types of habitat abutting natural versus replanted sites (7). Therefore, when possible, emphasis should be placed on protecting natural mangrove habitat.

Survey
The survey collected information on all income categories and on major categories for productive and consumable assets. . In addition, to the extent that the degree of recall bias is correlated with wealth (e.g., the poor may have more diverse income sources and hence have a more severe recall bias), we also partly control for these differences through the wealth categories which we include in the full model.
In addition to recall bias, we are concerned about the potential bias in the data regarding mangrove firewood collection because of the perceived risk of reporting an illegal behavior. To solicit information that is as accurate as possible, we did explain to the respondents at the outset of the survey that any information we collect will remain confidential, that it will not be shared with any other entities, and that they may refuse to respond to any question. Based on information from focus groups that we conducted after the survey, we have some indication that there could have been cases of underreporting among households who live in or adjacent to the park. However, our data show that there are few households who switched from mangrove to other types of firewood from 1990 to 2004 among households who live in or adjacent to the park. Therefore, although the absolute level of proportion of those who use mangrove firewood may be biased downwards, the switch information contains less bias.
In this study, we linked household survey data with mangrove cover data within a 5 km radius circle around each subvillage. Since all households are georeferenced, we could technically create the same variable at the household level. However, since most households are clustered within each subvillage, there is little variation in the location of the circular 5 km radius land cover analysis zone (and hence mangrove area). We therefore use the subvillage-level variable.

Geospatial Data and Methods
Landsat also be due to changes in mangrove areas outside SANAPA areas. Moreover, they also could be due to unobservable factors that affect both mangroves and mangrove-related income (such as community's ability in managing mangroves, shrimp, and fish) and location-specific factors that affect productivity of mangroves. We also need to control for selection bias in income activities.
To address these challenges, we employ Heckman's sample selection model for panel data (8). In general, a key advantage of the selection model is to control for sample selection biases that could otherwise arise from the existence of unobservable year (2004,2009). Let the equation that determines the sample selection be: where z it * is a latent variable for fishing income in year t for household i, z it =1 if z it *>0 and 0 otherwise, w it denotes the determinant of this status, γ t is associated parameter estimates, and u it is an error term. The canonical specification for this relationship is a probit regression of the form: where Φ is the cumulative distribution function of the standard normal distribution. In  Table S3. From the probit model estimates we compute the Inverse Mills Ratios (IMRs) for each year, defined as: where φ denotes the standard normal density function. Unfortunately, since we only have information on net earnings from fishing as a lump sum and not for specific species, we cannot control for these effects. We note that for this reason, most fisheries analysis will look for 'fishery independent' estimates of abundance change [e.g., a series of standardized stock surveys, (9)]. However, a critical advantage for this study of using income data is that we can directly observe the changes in households' welfare.
Unfortunately, our survey did not include direct questions about the reasons behind the behavioral change in effort allocation. The information we do have are qualitative information on the respondents' perceptions of the positive and negative effects of SANAPA. We do not attempt to identify causality using the answers to these questions partly because of lack of observations, lack of a convincing strategy, and high collinearity among questions. However, based on simple correlation coefficients, we find that those who lost land to crops due to establishment of SANAPA are associated with larger gains in fishing income between 2004 and 2009. We know through our focus groups that fishing and shrimping are some of the few (in some cases, the only) incomegenerating activities available in the area. This suggests that households could be changing effort allocation partly out of necessity when there are changes in other income sources, which could be driven by the establishment of a protected area.
However, because we cannot convincingly demonstrate this causality, we will refrain from speculating this in the main text.

Commercial and Artisanal Fisheries in Tanzania
The shrimp and fish species typically caught by the commercial trawlers and the artisanal fishermen varied due to the types of fishing gear employed. Double-rigged side trawlers were used in the commercial fishery, and the preferred fish species harvested included grunters, groupers, kingfish, catfish, cobia, and spiny turbots (10). lamps typically harvest anchovies, mackerels, and sardines (10,11). However, the majority of fishermen in our study area rely on seine nets (which are dragged off the beach at low tide) cast nets, mesh nets, mosquito nets, and fish traps. The seine-net fishery typically yields emperor, mackerel, parrotfish, rabbit fish, and sardines (10).
Research by Jiddawi et al. (12) found coral reef fishes such as emperors, goatfish, groupers, parrotfish, rabbit fish, snappers, surgeonfish, and sweetlips particularly important to the artisanal fishermen since they can access and harvest these species with their traditional fishing gear and crafts. The most common shrimp species harvested by the artisanal fishermen are P. monodon, P. semisulcatus, and F. indicus with the latter most prevalent when mesh nets are employed near river mouths or within the intertidal zone (10,13).

Ecosystem Impacts of Commercial Shrimping
Prior to the outright ban in January 2008, a series of regulations were created by the marketing and processing at the landing sites (14)(15)(16). In addition, TAFIRI put forth maximum sustainable yield (MSY) recommendations, but harvesting levels were twice the recommended amounts (17).
Although the prohibition of night trawling was meant to reduce conflict with artisanal fishermen, an unintended consequence of this policy was exacerbated damage to the bottom habitats as trawlers conducted heavier sweeps with tickler chains to dig up Penaeus semisulcatus, a nocturnal shrimp species (18). Regulations did not require turtle exclusion devices (TEDs) and bycatch reduction devices (BRDs). The net result was the harvesting of many unintended marine and estuarine species, as well as increased turbidity and habitat damage (14,16,18,19). To address these issues and concerns related to overfishing of the shrimp stock, trawling was banned outright in 2008 (20).
Bycatch species included seagrasses, sponges, sea cucumbers, starfish, crabs, fish, squid, sharks, rays, and sea turtles. Sphyraena obtusata (barracuda), and Terapon theraps (largescale grunter) (10,14,16,21). Clearly one would expect trophic interactions among the species. It is entirely possible that removal of a key species by one fishery could have significant effects in the other. However we have no empirical evidence or data which would allow us to identify such interactions.

Artisanal Catch Levels within Bagamoyo District
In Tanzania Figures S1 and S2). Further, the increase observed within Bagamoyo District may in part be due to the establishment of SANAPA and the subsequent protection of important nursery habitats; however we cannot draw any firm conclusions from the available fisheries data.

Future Monitoring
Given the lack of fisheries independent monitoring data, we could only infer the relationship between mangrove protection and increased fisheries production.
Therefore, we recommend the implementation of a series of standardized surveys to monitor changes in fish and shrimp abundance in the riverine and coastal mangrove habitat protected along the Wami River and Estuary over time so that future studies can 84 base analyses on empirical evidence. Precise details will be site specific, but important components to consider when designing and executing a fisheries monitoring program include a sound experimental and statistical design that is pragmatic (e.g., costs, sustainable funding, logistics), and encourages improvements in local assessment capacity.
Fisheries monitoring methods need to be reliable, repeatable, and conducted consistently over time for intra-and interannual temporal comparisons (22). To make these efforts comparable to other studies carried out in the Western Indian Ocean region, sampling regimes should be linked to life histories and habits of the species of interest during neap spring tides with stake nets (23)(24)(25). In addition, appropriate sample sizes for stock assessments and the inclusion of spatial and temporal controls are important considerations. The collection of other important physiochemical aquatic variables and mangrove characteristics such as structural complexity of the root system to track the extent of nursery habitat over time are also recommended. Table S1. Summaries of research articles pertinent to our study.

Al-Khayat and Jones, 1999. A comparison of the macrofauna of natural and replanted mangroves in Qatar
Study Location: Qatar. Date of Study: June 1993-June 1994. Purpose: To quantify decapod and fish biodiversity in a natural Avicenna marina mangrove, a ten-year old A. marina mangrove plantation, and a salt marsh to ascertain if pelagic biota recolonize replanted mangroves. Methods: Hand net fishing to capture juvenile and small fish, gill net (20m x 1.5m with 7cm mesh) and seine net (15m x 1.5 m with 5cm mesh) fishing to capture adults. Main relevant findings: 1) Natural mangrove areas had smaller sediment grain size and higher levels of organic material and substrate moisture in comparison to the planted mangrove areas 2) Overall species diversity ranged from 33-34 spp. among the natural sites, 3) The replanted Rhizophora site, which had the greatest structural complexity, exhibited the highest shrimp density whereas the highest small-sized fish density and biomass were observed in Avicennia sites located furthest inland. Relevant study conclusions: The successful shrimp and fish recolonization of the replanted Rhizophora habitat suggests that mangrove restoration can help to restore depleted fisheries (p. 233).

Bosire et al., 2004. Spatial variations in the macrobenthic fauna recolonisation in a tropical mangrove bay
Study location: Gazi Bay, Kenya. Date of study: Not specified, but the research was conducted five years after mangrove replanting. Purpose: To study the recolonization of macrobenthic fauna in replanted Avicennia marina, Rhizophora mucronata, and Sonneratia alba mangrove plantations. Methods: Crabs and sediment infauna were collected from randomly placed quadrats, identified, and counted. Main relevant findings: 1) Natural sites had the highest sediment infauna density with the exception of the reforested A. marina site.
2) The R. mucronata and A. marina reforested sites had higher crab densities than the natural forests, but the reverse pattern was observed within S. alba sites. Relevant study conclusions: Similarities in the number of taxa between natural and reforested sites suggests a recovery in habitat provisioning ecosystem services (p.1069).

Huxham et al., 2004. Mangrove fish: a comparison of community structure between forested and cleared habitats
Study location: Gazi Bay, Kenya. Date of study: 2002. Purpose: To compare the fish communities among natural, reforested, and cleared sites of Sonneratia alba, and Rhizophora mucronata. Methods: Stake netting with single (100m with 1mm mesh) and paired (24m with 1mm mesh) nets to capture fish. Main relevant findings: 1) Site 1, a S. alba plantation planted years before the study, had the highest mean abundance, biomass, and species richness of all mangrove sites, the second highest total number of species, and supported several species found only in mangroves. Relevant study conclusions: The findings suggest that reforested sites are capable of providing "suitable (or possibly superior) habitat for fish" (p.644). 2 of intertidal microhabitat). Main relevant findings: 1) A total of 1800 individuals from 49 taxa and 34 families were caught with five spp/taxa comprising ~70% of the total fish abundance. 2) Margalef's index of species richness ranged from 1.07 at restored site MP to 1.43 at restored site IP, and Shannon-Wiener diversity ranged from 0.66 at the natural site to 1.00 at the clear cut site. There were no statistically significant differences between any of the sites. 3) The clear cut site had the highest fish abundances while restored site MP had the lowest abundance, but highest fish biomass. Relevant study conclusions: 1) The insignificant differences between diversity values suggest that at this spatial scale, temporal patterns play a larger role in juvenile fish assemblages than the presence and type of mangrove (p.50). 2) Similarities in fish density, diversity, and community composition between the natural and replanted sites suggest that the refuge and foraging areas for juvenile fish has been restored in the replanted mangroves (p. 50). 3) Higher fish densities in the clear cut site may be explained by its small size and enclosure by mangrove habitat at a larger spatial scale (p. 50). Any positive impact of SANAPA on your livelihood (%) 24%*** 5% Notes: The respondent was asked whether they agree or disagree with each statement and to rate the response on an 11-point Likert scale. We rescaled the original numbers so that +5 indicated "strongly agree" and -5 indicated "strongly disagree". The numbers shown in the table are means. The last two rows show the percentage of households agreeing to the statement. ***, ** indicates that the difference between the two groups are statistically significant at the 1% and the 5% level, respectively.

Irrigation in a Free-Flowing River in East Africa: Impacts on Downstream Ecosystem Goods and Services Provided by a Coastal Protected Area
Catherine Specifically, we examine the following research questions: 1. What are the characteristics of the historic/pre-altered flow regime that have supported the ecosystem goods and services currently provided by the Wami River and its estuary? 2. How will proposed upstream irrigation withdrawals for biofuel production change the Wami River's flow regime? 3. How might the altered flow regime impact the ecosystem goods and ecosystem services utilized and valued by the different groups of downstream stakeholders?
Because water abstractions for irrigated agriculture are usually most intense during dry periods of the year, our analyses focus on changes in the extent and frequency of low flows.

Site Description
The

Hydrological Data Sets
With the assistance of water managers at the Wami Ruvu Water Basin Office, we obtained 24 years of daily flow data to generate a historical data set. The Mandera gauge, the most continuously active downstream gauge on the Wami River, is located at  Table 2).

Hydrological Analyses
Stream flow data are a continuous variable often summarized by frequency distributions. The values for the streamflow were ranked from smallest to largest and plotted using a Weibull distribution (Weibull, 1951) where: During the wetter portions of the year (April and May), the projected monthly withdrawals for the biofuel project were found to represent a relatively modest fraction of the average or median monthly river flows (Table 3). Abstraction requirements during the driest portion of the year (September to November) were comparatively more substantial constituting between 32 and 40% of the median monthly flow ( Table   3).  (Table 4).
Examining shifts in the low flow indices provides further evidence of the extent of change generated by the proposed project. With the historic flow regime, the Q99.5 for daily flows is 0.8 m 3 /s. That same magnitude of flow, however, would be observed with a Q95 frequency under the abstraction scenario (Table 4) (Table 5). Under the abstraction scenario, daily flow rates of zero were found to occur at a frequency of Q95 (1 out of 20 days) during one out of four years ( Table 6). As noted previously, based on historic records, zero flow rates were not even observed at the Q99.5 frequency. So, as well as extreme low flows occurring in more years, the number of years with extended periods of extreme low flows would also increase. From examination of the lower quartile of the distribution of annual flow indices, the 30 day Q95 with abstraction is lower than the 1 day Q99.5. Thus, one of 4 years would experience severe, prolonged droughts with abstraction.

Discussion
Our results demonstrate that new large scale water withdrawals must be (chapter 1 of this dissertation) found that many of the local residents rely on the river for potable water as well. They too will be forced to find other sources during the dry season either through well development or the import and purchase of water supplies.
The lack of flow will also disrupt river continuity, severely limiting the movement of aquatic organisms and disconnecting the estuary from the river system. marina, which is not widely used due to the soft nature of its wood, and reduction in X.
granatum, which is used for building furniture, would impact the availability of construction materials.
Changes in the riverine and estuarine vegetation will also alter the condition and availability of nursery habitat. These changes, in turn, will affect the distribution, composition and abundance of juvenile fish and invertebrates with resultant consequences on estuarine trophic interactions and coastal food chains (Ewel 2010). Wami River watershed and is not likely to be reduced with through additional watersaving practices.

Implications
Large, irrigated agricultural developments are likely to be incompatible with downstream protected areas in the arid watersheds of East Africa due to the high interannual and seasonal variability in stream flow. Although a proposed 10,500 ha biofuel operation would constitute less than 0.01% of the watershed, our analyses demonstrated that the water withdrawals will threaten biodiversity and other ecosystems goods and services that are intended to be protected by Saadani National Park, located at the terminus of the Wami River. We note that initial plans for the biofuel development called for a 17,000 ha operation -which would produce even greater impacts on the national park. Decision makers at the local, regional and national levels would ideally have access to tools and data that can provide rapid insights into the trade-offs from different levels of abstraction. In Figure 4, we illustrate the effects of different scales of water abstraction on the extent of zero flow periods within the Wami River. One hundred percent represents the abstractions associated with the 10,500 ha biofuel operation analyzed in this study. The relative scale simply reflects the withdrawals from a given percent of the full scale operation. Whereas the full scale operation will generate 300 days with zero flow occurring in 35 different events over the 24 years of record, an operation that requires 30% of the required water abstraction will generate 55 days of zero flow (~1/6 th of the amount predicted with the full scale system) over 9 different events. While this lower level of abstraction will generate less impacts than the full scale system, we are not able to estimate the loss of ecosystem services and thus cannot provide the information required by decision makers and stakeholders on the tradeoffs associated with any level of abstraction. In our study, we used the historical dataset as a means for looking at the potential effects of the proposed biofuel water abstractions, but recognize that there has been limited development within the watershed since 1978 that was not captured. We did not have information on the specific location and extent of abstractions in the watershed since 1978, and we did not account for shifts in climate so our results provide perspective.