Social valuation of mangroves in the Niger Delta region of Nigeria

Abstract

Worldwide, the mangrove ecosystem is in serious decline. The continuous conversion of mangrove vegetation to alternative usage is attributable to the lack of appreciation for the many ecological services, as well as products from the vegetation. As a result, seminal studies have been conducted severally to estimate the economic value of products and services derived from mangroves. However, mangroves also exhibit social value which has been called cultural services of ecosystems, cultural capital of ecosystems and sociocultural perspective of critical natural capital. The social value of mangroves is qualitative and thus antithetical, as well as distinguishable from quantitative economic value in which money is the natural common measurement unit. It is for this very reason that the social value of mangroves is often not captured for policy- and decision-making. This study, therefore, focuses on the social valuation of mangroves in the Niger Delta region of Nigeria using the following social value variables: therapeutic value, amenity value, heritage value, spiritual value and existence value. Results from household surveys conducted in Buguma, Burutu and Kuruama communities in the Niger Delta, as part of this study, revealed various degrees of social value for mangroves in the three communities. A major policy implication emanating from this finding indicates that the decision to convert mangrove vegetation in the Niger Delta to alternative use should be based on the consideration of the pluralism of the value of mangroves. This includes consideration for the economic as well as the social value of mangroves.

Keywords:

• social valuation
• economic valuation
• mangroves
• Niger Delta
• ecosystem
• sustainability

Introduction

Worldwide, mangrove ecosystems are in serious decline (Held et al. 2003). Mangrove forests once covered three-fourths of the coastline in the tropics and sub-tropical countries. Only about 50% of these forests remain today, and half of the remaining vegetation is degraded (Upadhyay et al. 2002). The continuous decline of the vegetation has been attributed primarily to unsustainable economic development, such as the conversion of mangroves into shrimp farms for short-term profit, only to abandon the farm after a few years, leaving the ecosystem polluted with aquaculture reagents (Aksornkoae 2004). According to the millennium ecosystem assessment report (2003), an estimated 35% of mangroves have been removed due to shrimp and fish aquaculture, deforestation and freshwater diversion. This is not surprising since prior to the 1960s, wetlands, including mangroves, were perceived as wastelands that could only be ‘improved’ through conversion to alternative use (Mitsch & Gosselink 1993). This may have as well been due to a lack of appreciation for the many ecological functions, products and services produced by wetlands. Nevertheless, some of the early references to the concept of wetlands functions, services, and their value can be traced back to the mid-1960s and early 1970s (e.g. King 1966; Helliwell 1969; Hueting 1970). However, in recent times, there has been tremendous increase in research focusing on the benefits of wetlands to human society and well-being (e.g. de Groot 1992, 1994; Pearce 1993; Bingham et al. 1995; Daily 1997a; Pimentel & Wilson 1997; Limburg & Folke 1999; Wilson & Carpenter 1999; Barbier 2000; Daily et al. 2000; Millennium Ecosystem Assessment 2003; de Groot et al. 2006; Barbier 2007).

Nonetheless, the seminal studies that revealed the economic value of environmental resources, such as the forest ecosystem, date back to two decades when Peters et al. (1989) published a two-page piece in Nature. They stunned the ecological community with their findings, which revealed that the non-timber forest products (NTFPs) from a 1-ha forest plot in Mishana (30 km from Iquitos, Peru) were worth $700. By adjusting for labour and transportation cost, the time-discounted net present value (NPV) of present and future harvests of fruits and latex alone was estimated at $6330 for a single hectare (Sheil & Wunder 2002). About eight years later, another publication appeared in Nature by Costanza et al. (1997), with the claim that ecosystem services provide global benefits of $33 trillion per year, a figure that was in excess of the world gross product by approximately 83%. There is also the recognition that the valuation of ecosystem goods and services as a policy tool was established through the pioneering work of Daily (1997a, 1997b), whose edited volume listed a different set of views on the links between specific ecological services and the economic benefits from such services (Howarth & Farber 2002). Consequently, as a response to the growing awareness of the value of wetlands, there is now substantial literature on wetland valuation, with the primary focus of informing environmental policies (Barbier et al. 1997; Bardecki 1998; Kazmierczak 2001). Many of the existing studies vary widely in the valuation techniques employed, the actual wetland products and services valued and the type and geographical location of the wetlands considered (Brander et al. 2006). A meta-analysis review of economic valuation of wetlands literature by Heimlich et al. (1998) identified 33 studies with values ranging from $0.06 to $22,050 per acre (Woodward & Wui 2001).

Although much of the wetland valuation literature is focused on the economic value of wetlands, however, wetlands, such as mangroves, also exhibit social values that are not directly ascribable to the ecological or the economic domain, but which are nevertheless essential for the proper functioning of society and human well-being (Chiesura & de Groot 2003). Such social value of wetlands has been variously called ‘cultural services of ecosystems’ (Millennium Ecosystem Assessment 2005), ‘cultural capital of ecosystems’ (de Groot et al. 2006), ‘socio-cultural perspective of critical natural capital’ (Chiesura & de Groot 2003) and ‘socio-cultural value of ecosystems’ (de Groot & Van der Meer 2010). The social value of wetlands within the context of this study is based on people’s view of their wetland for ethical, religious, cultural and philosophical reasons. Hence, for many people, wetlands are considered as source of subjective well-being¹ (SWB) that is closely associated with deeply held historical, communal, ethical, religious and spiritual values. Consequently, it is qualitative and thus antithetical, as well as distinguishable from quantitative economic value in which money is the natural common measurement unit. It is for this very reason that the social value of wetland is seldom captured for policy- and decision-making. Similarly, very little research has been conducted to qualitatively measure the social value of wetlands to society.

Frameworks for the social valuation of wetlands

From a social equity perspective, one crucial question that has generated heated debate in public discourse on the valuation of ecosystem goods and services is how such valuation should be conducted to ensure equity and fairness to communities and individuals who derive social value from such goods and services. As a result, some of the approaches proposed for capturing the social value of wetlands include economic valuation, discourse-based valuation, psycho-cultural approach, sociocultural perspective of critical natural capital and cultural capital of ecosystems.

Economic valuation framework

Resource economists consider cultural values and their social welfare indicators as a subset of economic value and thus should be determined using economic valuation (Barbier 1994; Freeman 2003). The approach is implemented as non-use value within the total economic valuation paradigm. The theoretical foundation of the framework is based on the neoclassical economic theory in which the utility maximization framework estimates value by ascertaining how much individual consumers of an environmental goods or services gain or lose from the use or non-use of the environmental resource, when the goods or services provided by such a resource decline or increase in quality or quantity (NRC 2005). The framework measures individual welfare, i.e. whether the individual is better off or worse off, as a result of the changes in the environmental services. Therefore, welfare measure is based on the assumption that for any individual, the different sources of utilitarian value to such an individual are substitutable so that, on aggregate, the individual utility remains unchanged (presumably at the maximum level, subject to income or budget constraints, and given the prices of all goods and services) (Freeman 2003). This approach has been applied to capture the total and incremental changes in ecosystems services within the framework of cost-benefit analysis for policy development (M. Kumar & P. Kumar 2008). However, economic valuation approach to the social value of wetlands has long been adjudged as inadequate for several reasons (Etzioni 1988; Bishop 1993; Jacobs 1995; Vatn 2000; Wilson & Howarth 2002; Chiesura & de Groot 2003; M. Kumar & P. Kumar 2008). First, economic efficiency is only one of diverse indicators that can guide environmental decision-making (Zendehdel et al. 2008). Other indicators include political and social factors. Second, the assumption that the environmental resource being value is private and thus has its property right well-defined is compromised by the public nature of environmental resource. Hence, property rights on such environmental resource are often not clearly defined (Vatn & Bromley 1997). Third, economic valuation is market-based, but ecosystem goods and services being valued do not necessarily enter the market and thus lack reliable price signals (Samuelson 1954). In response to this criticism, non-market methods, such as stated preferences, have been proposed to accommodate the public nature of environmental resources (Krutilla 1967; Boyle & Bishop 1987; Mitchell & Carson 1989; Loomis 1992; Bishop & Welsh 1993; Pearce & Moran 1994; Carson & Hanemann 2005).

One of the widely used stated preference methods is the contingent valuation approach that elicits willingness to pay for the conservation of an environmental resource or willingness to accept compensation for the alternative use of the resource. However, the contingent valuation method has received considerable criticisms coming from economic (Hausman 1993; Diamond & Hausman 1994; Knetsch 1994; Vatn 2004), political (Sagoff 1998a; Smith 2003; Spash 2007) and psychological fields (Kahneman et al. 1999; Spash & Vatn 2006; Spash 2007; Zendehdel et al. 2008). First, the assumption that all individuals have the required utility function for their responses to contingent valuation questions, used in valuing social equity on environmental resources, has been contested by some authors including Common et al. (1997) and Sagoff (1988b). In fact, Sagoff (1988b) would argue that when individuals make decisions about the environment, they do so as ‘citizens’ and not as ‘consumers’. As a result, the individual considers issues of cost benefit analysis to the nation as whole, and this involves consideration of sentimental, historical, ideological, cultural, aesthetic and ethical values (Common et al. 1997). Moreover, a range of broadly rights-based or deontological positions do appear to be relevant to the general public when considering the environment (Spash 1997), and as such have important implications for the responses to contingent valuation questions (Spash 2000). Second, the respondents in the contingent valuation method are insensitive to the scope of the environmental resource being valued (Liljas & Lindgren 2001; NRC 2005). Therefore, the responses are subjective and do not vary with respect to variation in the scope and size of the environmental resource being valued. Given these shortcomings, other modified contingent valuation frameworks have been proposed. They include the use of choice experiments (CE) and deliberative monetary valuation (DMV) to elicit stakeholders’ preferences towards environmental criteria (Spash 2007). Although these methods have some advantages over the contingent valuation approach for constructing and eliciting stakeholders’ preferences, the methods still require people to make trade-offs between environmental criteria (Vatn 2004). However, the concept of value pluralism in environmental valuation related to ‘incommensurability and incomparability of environmental values’ restricts making trade-offs between environmental criteria (Liljas & Lindgren 2001; Smith 2003; Vatn 2004; Zendehdel et al. 2008). Sequel to the challenges associated with economic valuation, other valuation frameworks have been proposed to complement the economic valuation framework, particularly when equity and social fairness are under consideration (Richards & Davies 1999; Chiesura & de Groot 2003; Millennium Ecosystem Assessment 2005). These approaches are presented in the following section.

Discourse-based valuation

The discourse-based valuation framework (Coote & Lenaghan 1997; Jacobs 1997; Perkins 2001; Wilson & Howarth 2002) emanated from a convergence of arguments from economics, social psychology, decision science and political theory. Its basic principle is based on the assumption that the valuation of public goods, such as the social value of ecosystems, should result not from the aggregation of separately measured individual preferences, but from a process of free and open public debate (Habermas 1984; Dryzek 1990; Fishkin 1991; Wilson & Howarth 2002). Therefore, the social value of ecosystem services should be determined from an open debate with participants drawn from the community were such an environmental resource is located. Within this framework, social equity issues of interest to the community are addressed. A major strength of this theoretical framework is that local communities (applying their local knowledge) are involved in decision-making and the equitable valuation of their environmental resources. But evidence from social psychology suggests that small groups may not be very efficient at pooling unshared information to reach consensus, thereby leading to suboptimal results (Stasser & Titus 1985; Stasser & Stewart 1992; Stasser et al. 1995; Wilson & Howarth 2002). Consequently, the administration of survey instrument at the individual or household level to elicit individual unit-based information has been suggested as a complementary approach to discourse-based valuation (Kaplowitz & Hoehn 2001).

Psycho-cultural perspective framework

The psycho-cultural valuation perspective proposed by M. Kumar and P. Kumar (2008) would argue for the initiation of a ‘transdisciplinary’ dialogue aiming at reciprocal alliance and cooperation between natural and social science research through debates on environmental ethics, tools and methods of social inquiry and socio-economic development as well as empowerment. The goal is to bring these disciplines together to determine the appropriate framework for the valuation of ecosystem services. This framework is built on two components. First is the intrinsic value (such as aesthetic, moral and cultural values) of ecosystem services, and second is the mapping of ways in which the interactions between man and his natural environment have a bearing upon his psychological well-being. They further argue that results from studies in developmental and moral psychology indicate that majority of people base moral choice, and subsequently trade-offs, on social norms, affective reactions and moral intuition, rather than on analytical moral reasoning as obtained in economic valuation framework (M. Kumar & P. Kumar 2008; Menzel & Wiek 2009). Hence, the psycho-cultural perspective to valuation of ecosystem services brings the need for the concept of ecological identity, interdisciplinarity in approach and methodological pluralism in outlook.

Sociocultural value framework

The framework applies the concept of critical natural capital within the framework of sociocultural value to elicit values of nature which are not directly quantifiable in monetary terms (i.e. amenity, health, education and symbolic meanings), but which belong to the ethical, spiritual and affective realm of human beings, and which reflect the intangible dimensions of human-nature relationship (Chiesura & de Groot 2003). The primary focus of this framework is the human being situated within its social and psychological context, its non-materialistic needs, its understanding of well-being and the rational, as well as the emotional components of its attitudes towards the natural environment. This framework is derived from empirical research in environmental psychology and landscape planning which demonstrates that there is indeed a strong non-monetary relationship between human and nature (e.g. Ulrich 1984; Hartig et al. 1991; Schroeder 1991; Coley et al. 1997). As a result, social valuation of ecosystems directs the valuation exercise towards public debate, discursive and deliberative processes and qualitative appraisal rather than to the market (Chiesura & de Groot 2003).

Natural capital of wetland services framework

The natural capital of wetland services framework for accounting for the social values of wetland ecosystem consist of disaggregating the social value attached to wetlands into the following components: therapeutic value, amenity value, heritage value, spiritual value and existence value (de Groot et al. 2006). This is based on the paradigm that for many people, natural systems, including wetlands, are a crucial source of non-material well-being through their influence on physical and mental health and historical, national, ethical, religious and spiritual values (Millennium Ecosystem Assessment 2003). Some of the methods that have been proposed to measure the various social value components include checklist, administration of questionnaires, interviews and visual media (Guijt & Hinchcliffe 1998; Brown et al. 2001; de Groot et al. 2006).

Methods

Study area

The Niger Delta (shown in Figure 1), with a spatial extent of 75,000 km², is the largest Delta in Africa and consists of primarily a vast sedimentary basin derived from the natural Delta of the Niger River. The region is significant on account of the hydrocarbon deposits from which Nigeria export about 2.4 million barrels per day; this accounts for over 90% of Nigeria’s foreign exchange earnings. With such production output, Nigeria is a member of Organization of the Petroleum Exporting Countries (OPEC), the largest exporter of crude oil in Africa, fifth largest exporter to the United States (accounting for 14% of US oil consumption) and seventh largest exporter in the world. The low sulphur and high-quality crude (called Bonny Light) from the Niger Delta makes Nigeria’s crude oil lucrative and attractive to foreign buyers (Watts 2004).

Figure 1. Niger Delta Region of Nigeria and location map in Nigeria.

The Niger Delta region is also significant on account of the vast geographic spread of mangrove vegetation in the region. The region is home to three endemic families of mangrove vegetation represented by five plant species and one introduced family of exotic species. The endemic families are Rhizophoraceae family (red mangrove), consisting of Rhizophora racemosa, R. harrisonii and R. mangle species; the Avicenniaceae family (white mangrove) made up of Avicennia africana species; and the Combretaceae family consisting of Laguncularia racemosa species. The Arecaceae (Palmaceae) is the only introduced family consisting of Nypa frutican exotic species. The mangrove ecosystem in the region consists of the whole complex of swamp terrain, mudflats, mangrove trees, creeks, drain canals, the invertebrate and vertebrate fauna and micro-organisms and the interacting physio–chemical factors, such as temperature, salinity and tides associated with the system (Moses 1985). In the Niger Delta, the mangrove ecosystem is extensive and spreads across the following states: Ondo, Edo, Delta, Bayelsa, Rivers, Akwa-Ibom and Cross Rivers. Approximately 80% of the vegetation is found in Delta, Bayelsa and River States (World Bank 1995); hence this study is focused on the mangrove vegetation in these three states. The mangrove vegetation in the region is the largest contiguous mangrove forest in Africa. It is shielded from sea water, a characteristic that differs from that of several other African countries where the mangroves are directly exposed to sea water (NDES 1997). Plant products constitute a substantial amount of the goods extracted from the mangrove ecosystem in the Niger Delta, both at the subsistence and commercial levels (Saenger et al. 1983; Hamilton & Snedaker 1984; Focus Group 2008). Some of the goods extracted from the mangrove vegetation by the communities in the region include the following: fuelwood, charcoal, timber material for building, wood chips for stacking fish, salt, billets, railway sleepers, tannins, dyes and food (Macnae 1968; Walsh 1974; Hamilton & Snedaker 1984; Abuodha & Kairo 2001; Saenger 2002; Focus Group 2008). These goods are tied to the fabric, lifestyle, culture and livelihood of the various communities in the mangrove ecosystem of the region. Furthermore, these products are some of the major sources of livelihood for the coastal communities in the region. As a result, the economic value of the various components of the mangrove ecosystem in the region is significant. However, the vegetation is highly undervalued by policymakers and stakeholders in the region. For example, the transnational oil corporations operating in the region use a compensation rate of $24 for each hectare of mangrove destroyed or degraded (UNDP 2006). The United Nations Development Program (UNDP 2006) study found that this compensation rate was determined without adequate consultation or input from the host communities and so lacked the transparency and fairness required for peaceful or sustainable engagement (UNDP 2006).

This is corroborated by the finding that an hectare of mangrove in the region has a potential yield of between $642/ha – $2853/ha (James et al. 2011). Moreover, the social value of mangroves in the region has neither been determined nor published in public domain. It is this lack of equitable valuation for the mangroves in the region that has encouraged the unsustainable use of the ecosystem and thus threatens the continuous existence of the forest in the Niger Delta. Hence, the thrust of this study is to determine the social value of mangroves in the Niger Delta.

Social valuation framework

For many coastal communities living within the mangrove ecosystem of the Niger Delta, they derive non-material well-being through cultural, historical, spiritual, aesthetic, ethical and recreational values (Focus Group 2008). As a result, the natural capital of wetland services framework proposed by de Groot et al. (2006) was adapted in this study to qualitatively measure the social values ascribed to the mangroves by the Niger Delta communities. The framework is presented in Figure 2 and it provides for the measuring of the following variables: therapeutic value, amenity value, heritage value, spiritual value and existence value (adapted from de Groot et al. 2006). Each of these variables was qualitatively measured by combining focus group and household surveys methods (de Groot et al. 2006).

Figure 2. The social value framework (Adapted from de Groot et al. 2006).

Therapeutic value

Therapeutic value includes the provision of medicines, clean air, water, soil, space for recreation and outdoor sports, and general therapeutic effects of wetlands on peoples’ mental and physical well-being. The basic indicators for measuring this value are suitability and capacity of mangroves in the provision of ‘health services,’ restorative and regenerative effects on people’s performance, and socio-economic benefits from reduced health costs and conditions.

Amenity value

Amenity value stems from the important role of wetlands in cognitive development, mental relaxation, artistic inspiration, aesthetic enjoyment and recreational benefits. The indicators for measuring amenity value include aesthetic quality of landscapes, recreational features and use, artistic features and individual preference. An example of the amenity value of wetlands is the natural scenery that the mangrove ecosystem provides when viewed from a distance.

Heritage value

Heritage value of mangroves is the role of the vegetation as reference for personal or collective history and cultural identity. It is a communal value and may include historic sites, features and artefacts, designated cultural landscapes, cultural traditions and knowledge. In recognition of heritage value, the UNESCO World Heritage System has continued to declare some areas as Heritage Sites for their aesthetic, historic and cultural relevance.

Spiritual value

Spiritual value indicates religious and spiritual significance of mangrove vegetation. Indicators of spiritual value include the presence of sacred sites or features in mangroves; such sites may include shrines where spiritual worship is conducted or specific mangrove trees marked for worship and reverence. Other indicators of spiritual value include the role of mangrove vegetation in religious ceremonies and development of sacred texts.

Existence value

Existence value (also referred to as ‘warm glow-value’) is a measure of the importance attached to some of the non-use properties of mangroves by local communities living within or in proximity to the vegetation. Such attachment can be for ethical reasons (intrinsic value) or intergenerational equity (bequest value). One of the major indicators for measuring the existence value is the preference for protecting the mangrove vegetation based on ethical reason.

Primary data collection

Focus group discussions and household surveys were used to collect the primary data sets used to qualitatively estimate the social value of the mangrove vegetation in this study. Hence, as part of this study, field trips were conducted in the Niger Delta for primary data collection in 2007 and 2008. The focus group sessions and household surveys were conducted in the following Niger Delta communities shown in Figure 3: Buguma and Kuruama in Rivers State, and Burutu in Delta State. These communities were selected because they represent the ethnic and geographic distribution of communities found within the mangrove ecological zone in the region. In addition, Buguma and Burutu represent large communities within the mangrove ecological zone, while Kuruama is an example of a small community within the zone. Given the nature of this study, ethical clearance was sought from the paramount traditional ruler of each of the three communities before conducting the focus group sessions as well as the household surveys.

Figure 3. The communities surveyed in the Niger Delta.

Focus group sessions

Focus group sessions were conducted in Buguma, Kuruama and Burutu communities with 24, 20 and 24 participants, respectively. The participants were drawn such that they represented stakeholders in each community. These stakeholders included community elders, women, fishermen and youths. Each session was conducted in an atmosphere of ease, and all the participants had equal chance of participation. As a result, no speaker was hindered by external compulsion or pressure. Similarly, participants were allowed to express their own attitudes, needs and preferences for the social services from mangroves. Each session was conducted in English language, and a local interpreter was hired to translate all the discussions into the local dialects. The findings from the focus group sessions were used to develop the survey instrument that was deployed for the social valuation of mangroves in the three communities. After developing the questionnaire, it was pretested on the focus group participants and some questions were thereafter rephrased to test the alertness of the respondents. The involvement of the communities at the inception of the instrument development was to ensure that the survey instrument was culturally relevant to the communities in which the survey will be conducted. In addition, it was an opportunity for the communities to make contributions to the estimation of the social value of the mangrove vegetation in their community.

Survey instrument

The survey instrument consisted of two sections. The first section sought for socio-economic information of the respondent, such as education level, occupation, age group, length of stay of respondent in the community and household income. The second section is presented in Table 1 and consisted of questions required to qualitatively measure the variables in the social valuation framework (i.e. therapeutic value, amenity value, heritage value, spiritual value and existence value). All the questions in the survey instrument consisted of closed-ended type of questions. This type of question was used for the ease of coding during analysis. In addition, such a structure enhanced the ability of respondents to provide absolute answers to questions; hence they could either respond ‘Yes’, ‘No’ or ‘I don’t know’. All the ‘I don’t know’ responses were not included in the final result analysis. In addition, most of the questions were structured such that a ‘Yes’ response to a question indicated support for the social value variable being measured, while a ‘No’ response indicated a dissent. However, the questions rephrased to test the alertness of respondents were exempted from this rule, e.g., if the mangrove forest in your community was completely cleared, will that make your community look better? A ‘No’ response implies support for the social value variable being measured, while a ‘Yes’ response implies a dissent. Each variable was thereafter measured by aggregating the affirmative responses. Thereafter, the mean of the percentage distribution of the affirmative responses was estimated using Equation (1).

Table 1. List of questions used to measure the social value of mangroves.

Id	Social value variables and questions used to measure them	Yes	No	I don’t know
	Therapeutic value
H1	Does the mangrove provide medicinal resources for your community?
H2	Has the medicinal resources from the mangrove in your community reduced the number of patients in the community clinic?
H3	If you had no community clinic, can the resources from the mangroves cure the common sicknesses in your community?
H4	Does the health of your community dependent on the good health of the mangrove?
	Amenity value
H5	Does the mangrove add natural beauty to your community?
H6	Does the mangrove in your community provide space for community relaxation and enjoyment?
H7	Have you learnt anything about the mangrove that you would not have learnt if the mangroves were not in your community?
H8	If the mangrove forest in your community was completely cleared, will that make your community look better?
	Heritage value
H9	Is the mangrove a very important aspect of your community’s history?
H10	Does the mangrove play any important role in your culture and tradition?
H11	Does your community view the mangrove as heritage from your forefathers?
H12	Would you like the mangrove in your community to be in existence for the future generation of the community?
	Spiritual value
H13	Does the mangrove serve as the foundation for your community’s spiritual beliefs?
H14	Does your community use materials from the mangrove for spiritual worship?
H15	Does your community perform any spiritual worship in the mangrove?
H16	Does your community attach any myth to the mangrove?
	Existence value
H17	Do you think it is the duty of the community to protect the mangrove from destruction, regardless of the cost?
H18	Does the mangrove have a right to exist, even if you do not derive any benefit from the vegetation?
H19	If you have money, are you willing to pay to protect the mangrove from destruction?
H20	Do you think it is fair to destroy the mangrove?

(1)

where:

µ_kv = Mean percentage distribution of affirmative response for social value variable (k) in community (v).

P_ikv = Percentage distribution of affirmative response to each question used to measure variable (k) in community (v).

i = Question used to measure variable (k).

N = Total number of questions used to measure variable (k).

K = Variable used to measure social value (therapeutic, amenity, heritage, spiritual and existence).

v = Community where survey was conducted.

Household survey

The final phase of the primary data-gathering process involved the administration of the survey instrument developed from the focus group discussions. The sample size was estimated at the 90% confidence interval and 95% confidence level, resulting in a minimum of the following sample sizes: 87, 85 and 55 from a population size of 900, 700 and 128 households in Buguma, Burutu and Kuruama communities, respectively. However, to accommodate redundancy, the survey instrument was administered to 136, 155 and 60 households in Buguma, Burutu and Kuruama communities, respectively. Participants in the household survey were selected based on the quasi-systematic random sampling procedure. The sampling approach was implemented as follows: Four survey teams were deployed in each community with each team responsible for a quadrant of the village. The starting point for all the teams was always the village square at the geographic centre of each community. From the village square, each team moved into its assigned quadrant and visited the first household in the quadrant to begin the survey. After visiting the first household, every other household was then visited to administer the survey instrument. The sampling approach was adopted because of the lack of spatial information for the households in the study communities. Moreover, a detailed map of the communities was not available during the data-gathering process. Also, other methods such as the simple random sampling could not be adopted because it was a major challenge to reference all the households in the communities that were visited.

Results and discussion

Socio-economic characteristics of respondents

Although the survey instrument was administered to 136, 155 and 60 households, only 126, 150 and 60 questionnaires were validated in Buguma, Burutu and Kuruama, respectively. As a result, 10 questionnaires were voided in Buguma while 5 were voided in Burutu due to incompleteness. A summary of results for the socio-economic characteristics of respondents is presented in Table 2. The majority of household respondents that participated in this survey were male household heads. They accounted for 60% of respondents while female household heads constituted 40%. Most of the household heads sampled were within the age bracket of 41 years and above; they constituted 59% of the respondents. On average, the respondents had lived in their community for 29 years. With reference to the educational background of the respondents, 37% had completed their secondary education, while 33% had primary level education. This is not surprising because the majority of those with higher educational background are more likely to migrate to the cities for better opportunities. The majority of those sampled (67%) reported the extraction of mangrove resources as their full-time occupation. The extraction of these resources is at the subsistence level. Nine out of every 10 household respondents extract fishery resources within the adjoining community rivers and creeks. The reported average monthly income of respondents was N18,694 ($130).

Table 2. Summary of the socio-economic background of survey respondents.

Variable	Buguma community	Burutu community	Kuruama community	Mean
Gender
Male (%)	67	62	51	60
Female (%)	33	38	49	40
Age group
40 years and below (%)	31	42	49	41
41 years and above (%)	69	58	51	59
Respondents average years of residence in the community (years)	35	25	26	29
Education
Primary education (%)	30	36	34	33
Secondary education (%)	47	30	34	37
Others (%)	23	34	32	30
Occupation (Extraction of mangrove resources) (%)	72	64	64	67
Average monthly income (US$)	186	117	88	130

Social value variables

Summary of results showing the percentage distribution of the respondents with affirmative responses to survey questions, as well as the mean of the percentages, are presented in Tables 3–7, corresponding to the following social valuation variables: therapeutic, amenity, heritage, spiritual and existence values, respectively.

Table 3. Results from affirmative response to questions for measuring therapeutic value.

Id	Survey questions used to measure therapeutic value	Buguma community (%) (n = 126)	Burutu community (%) (n = 150)	Kuruama community (%) (n = 60)
F1	Have you ever been treated with medicinal herbs from the mangroves in your community?	89	85	16
F2	Has the medicinal resources from the mangrove in your community reduced the number of patients in the community clinic?	65	67	6
F3	If you had no community clinic, can the resources from the mangroves cure the common sicknesses in your community?	71	67	6
F4	Does the health of members of your community depend on the proper functioning of the mangrove?	57	54	28
	Mean	71	68	14

Therapeutic value

Results from the household survey presented in Table 3 revealed variation in the therapeutic value ascribed to mangrove by the three communities that participated in this study. While 85% of households claim they have been treated with medicinal herbs from mangroves in Burutu community, 89% of households made the same claim in Buguma community. In fact, the percentage of households that derived medicinal resources from mangroves plummeted to 16% in Kuruama community. This is not surprising because findings from the focus group discussions conducted in this study revealed that mangrove vegetation is extensively used in Burutu and Buguma communities for curing health-related problems. Some examples include the liquid extract from the leaves of the Rhizophora species is used to cure open sores; the same leaves are used to cure skin rashes in infants, stomach ache and diarrhoea. Women also use the leaves to reduce belly fat after baby delivery. In addition, the chewing of Rhizophora propagule prevents novice sailors from experiencing sea sickness during their first couple of trips into the open ocean. In contrast, most members of Kuruama community interviewed claimed to be unaware of such usage of the mangroves. Focus group discussions in the community revealed that the community has access to medical facilities in Bonny Island which is about 20 min by boat ride. Bonny Island is home to the multibillion-dollar Nigerian Liquefied Natural Gas project. This accounts for the low (14%) aggregate positive response to the therapeutic value in Kuruama community as shown in Table 3.

Table 4. Results from affirmative response to questions for measuring amenity value.

Id	Survey questions used to measure amenity value	Buguma community (%) (n = 126)	Burutu community (%) (n = 150)	Kuruama community (%) (n = 60)
F5	Does the mangrove add natural beauty to your community?	71	71	78
F6	Does the mangrove in your community provide space for community relaxation and enjoyment?	72	55	60
F7	Have you learnt anything about the mangrove that you would not have learnt if the mangroves were not in your community?	70	64	62
F8	**If the mangrove forest in your community was completely cleared, will that make your community look better?	71	70	92
	Mean	71	65	73

Note: **denotes test question for alertness.

Table 5. Results from affirmative response to questions for measuring heritage value.

Id	Survey questions used to measure heritage value	Buguma community (%) (n = 126)	Burutu community (%) (n = 150)	Kuruama community (%) (n = 60)
F9	Is the mangrove a very important aspect of your community’s history?	96	91	75
F10	Does the mangrove play any important role in your culture and tradition?	98	86	75
F11	Does your community view the mangrove as heritage from your forefathers?	87	80	71
F12	Is there any historic site inside your mangrove forests?	88	89	60
	Mean	92	87	70

Amenity value

There is a general consensus among respondents from the three communities sampled that the mangroves provide space for relaxation. This is particularly a vital function for fishermen and those who collect fishery resources; they seek shelter under mangrove shades when it is raining or when the heat intensity of the sun is very high. They also prefer to enjoy the evening breeze under mangrove shades while they wait for the tides to subside for optimal fish harvest. This is indicated in Table 4, where on average 71% of households sampled in Buguma acknowledge the amenity function of the mangrove, while 65% and 73% made the same claim in Burutu and Kuruama communities, respectively.

Heritage value

The mangroves constitute a major heritage for the respondents who participated in this study. This is corroborated by the high percentage distribution (Buguma – 92%, Burutu – 87% and Kuruama – 70%) of affirmative response to the questions used to measure the heritage social value shown in Table 5. Findings from focus group discussions in Buguma community revealed that the annual masquerade festival in Buguma community commences in the mangrove forest. The Masqueraders dress up in the mangroves and perform certain rites before entering the community. Also, it is the culture of Buguma community to bury some of their dead in the mangroves forest, including children who die at a tender age (less than 10 years old); community members who drown in a river; anyone with an open sore at the time of death; and pregnant women who die before giving birth. Moreover, the trunk of the Rhizophora mangrove species (called Kokari in the native dialect) is used to settle disputes between aggrieved parties in the community. The practice is to make the warring party swear using the trunk of the Rhizophora racemosa mangrove vegetation. Similarly, focus group sessions in Burutu community revealed that the community use the ash residual from burnt mangroves for painting the bodies of their young women during traditional dancing festivals. In addition, some sections of the mangroves in the community are considered evil forests, and visits to such forest are prohibited. These cultural practices that are tied to the mangroves clearly demonstrate the role of mangroves in the culture and tradition of the sampled communities. Furthermore, when respondents were asked, ‘Does the mangrove play any important role in your culture and tradition?’ 98% responded ‘Yes’ in Buguma community; likewise, 86% responded ‘Yes’ in Burutu community, while 75% responded in the affirmative in Kuruama community.

Spiritual value

To a large extent, the advent of Christianity in the three communities visited has gradually reduced community participation in the traditional religious activities that involve the use of mangrove materials. Nevertheless, some religious rites are still being practiced using materials from mangrove forests. The roots of Rhizophora mangrove species are used to beat drums during the annual Masquerade festival in Buguma community. When survey participants were asked whether they use materials from the mangrove for spiritual worship, 78% of them responded ‘Yes’ in Buguma community; while 69% and 35% responded ‘Yes’ in Burutu and Kuruama communities, respectively. This pattern was also indicated in Table 6 were the aggregate responses in support of the spiritual value of mangrove was 76% in Buguma, 68% in Burutu and 44% in Kuruama communities.

Table 6. Results from affirmative response to questions for measuring spiritual value.

Id	Survey questions used to measure spiritual value	Buguma community (%) (n= 126)	Burutu community (%) (n= 150)	Kuruama community (%) (n= 60)
F13	Does the mangrove serve as the foundation for your community’s spiritual beliefs?	78	60	43
F14	Does your community use materials from the mangrove for spiritual worship?	78	69	35
F15	Does your community perform any spiritual worship in the mangrove?	82	73	60
F16	Does your community attach any myth to the mangrove?	66	70	39
	Mean	76	68	44

Existence value

Most of the respondents in the survey pledged their support for the continuous existence of mangrove vegetation since their survival depends on the environmental resource. Moreover, they are keen at transferring the vegetation to the next generation, just as it was transferred to them. One of the respondents put it plainly when he said, ‘Burutu community is mangroves and mangroves is Burutu community. The historical account of the community is not complete without the role of mangroves in the community’. The respondents stressed the notion that they all grew up to know the mangroves and they will hopefully pass the vegetation on to their children, just as it was passed on to them by their parents. A participant in the focus group session conducted in Kuruama community also noted that the vegetation was transferred to them by their grandparents and they feel it is their duty to transfer the vegetation to their children. This notion was further buttress when survey participants were asked if the mangrove has a right to exist, even if they did not derive any benefit from the vegetation. In Buguma community, 91% of respondents answered ‘Yes’, while 89% agreed that the vegetation has a right to exist in Burutu community. Similarly, in Kuruama community, 68% of respondents agreed that the vegetation has a right to exist. This is presented in Table 7.

Table 7. Results from affirmative response to questions for measuring existence value.

ID	Survey questions used to measure existence value	Buguma community (%) (n = 126)	Burutu community (%) (n = 150)	Kuruama community (%) (n = 60)
F17	Do you think it is the duty of the community to protect the mangrove from destruction regardless of the cost?	92	91	97
F18	Does the mangrove have a right to exist, even if you do not derive any benefit from the vegetation?	91	89	68
F19	If you have money, are you willing to pay to protect the mangrove from destruction?	95	88	98
F20	**Do you think it is fair to destroy the mangrove?	85	91	93
	Mean	91	90	89

Note: **denotes test question for alertness.

Conclusion

Human society has and will always be faced with the decision of how to manage ecosystems for sustainability. This is also true for the mangrove ecosystem that has often been converted to alternate use, based on only economic consideration by policymakers. As a result, findings from this study are significant for many reasons. First, the mangrove ecosystem in the Niger Delta provides natural functions as well as services which influence people’s SWB through social structures, health and culture, both at the individual and the community levels. As a result, it is essential to assess the social value of mangrove and communicate such to policymakers for them to consider the social–cultural consequences of the conversion of mangrove vegetation to alternative usage. Second, this study revealed the existence of social value ascribed to mangroves by the Niger Delta communities that participated in this study. Across the mangrove ecological zone of the Niger Delta, communities ascribed preferences for the following social values of mangroves: therapeutic value, amenity value, heritage value, spiritual value and existence value. Third, the decision to conserve or change mangrove vegetation to alternative usage in the Niger Delta should be determined within economic as well as social value frameworks. The results from economic valuation are subjective, and so should be complemented with additional qualitative information from the social value of mangroves. Fourth, finding from this study has shown the dynamic nature of tastes and preferences, most especially in the long run. Although the preference for the social value of mangroves is significant in Buguma and Burutu communities when compared with Kuruama community, however, the negative influence of external factors on these social value variables may in the long run erode the significance of the social value of mangroves in the Niger Delta. For example, the advent of Christianity in the region has gradually diminished the role of mangroves in spiritual worship. Similarly, the influence of Bonny Island (an urban area) on Kuruama mangrove community was revealed in their low preference for the therapeutic, as well as spiritual value of mangroves in the community. Finally, a major policy implication of this study indicates that the decision to convert mangrove vegetation in the Niger Delta to alternative use should be based on the consideration of the pluralism nature of the value of mangrove vegetation that includes economic value as well as social value.

Notes

^1. According to Diener et al. (1999), SWB is ‘a broad category of phenomena that includes people’s emotional responses, domain satisfactions, and global judgments of life satisfaction.’ Within the framework of SWB, the social value of wetlands is centred on the notion of human happiness and satisfaction from the non-monetary benefits derived from wetlands.