Local Ecological Knowledge Reveals Change in Seagrass Social–Ecological Systems

Abstract

It is widely recognized that humanity is currently facing multiple planetary crises, including the widespread loss of biodiversity and a rapidly changing climate. The impacts of these crises are often far reaching and threaten food security (SDG goal two: zero hunger). Small-scale fisheries are estimated to provide livelihoods for over one hundred million people and sustenance for approximately one billion people but face a plethora of threats and challenges linked to planetary crises. In this multi-country assessment (150 coastal villages across five countries within the Indo-Pacific), household interviews revealed how seagrass meadows are important to small-scale fisheries, particularly as a place to find and collect a reliable source of food. Interviews also revealed that habitat loss and the over-exploitation of these resources are placing people and their food security at risk. This study exposed how dynamic local ecological knowledge can be, uncovering personal opinions and responsibilities that result in the hybridization of knowledge. Here, we demonstrate the importance of using local ecological knowledge to incorporate shared values into management but also highlight that an integrated approach, pairing local and conventional scientific knowledge, is needed urgently if we are to meet the needs of people while simultaneously conserving biodiversity.

1. Introduction

Food insecurity and biodiversity loss are key challenges facing humanity [1], which the United Nations Sustainable Development Goals seek to address [2]. Stable and resilient coastal and marine environments are critical to addressing both, yet these environments are subjected to an increasing number and intensity of human pressures [3]. The levels of anthropogenic disturbance are disproportionally higher in coastal environments [4], where human populations are large and increasing. Tropical coastal ecosystems in particular are experiencing rapidly increasing pressures [4]. These systems support diverse, productive ecosystems that encompass multiple habitats, from coral reefs, mangroves, and seagrass meadows to sandy marine and estuarine environments [5].

Tropical coastal ecosystems are threatened by a myriad of anthropogenic factors including overexploitation, direct physical impacts, nutrient pollution, and climate change [3]. These impacts undermine and impair ecosystem function, lessening their ability to provide critical ecosystem services including biodiversity support [6]. The loss of this biodiversity support function subsequently impacts the provision of fisheries, water purification, and coastal protection services [7]. Seagrass meadows are an important coastal habitat that provides numerous ecosystem services [8,9,10], not least in the tropical Indo-Pacific region, which boasts the highest seagrass diversity [11], despite a trending decline in extent [12]. In this region, seagrass meadows are threatened by local stressors including, but not limited to, overfishing, seaweed farming, gleaning, and coastal development [13,14,15,16,17,18,19].

Seagrass meadows within the tropical Indo-Pacific bioregion have typically provided rich fisheries, e.g., [20,21,22], which are supported by the complex habitat that seagrass meadows provide [23]. Recent research has highlighted how socioeconomic factors are key in determining how and why seagrass meadows are used by people [24]. However, understanding the changing complexity of these fisheries in terms of their economic, cultural, institutional, and social values, and the diverse peoples that utilise them, against a backdrop of habitat decline is a key challenge. To support sustainable seagrass systems, there is a need to better manage them as a coupled social–ecological system of which people are an important part [25], not least to avoid unintended consequences and failure [26]. Tropical Indo-Pacific fisheries are largely data deficient, and the use of local ecological knowledge (LEK) has been highlighted as a tool to obtain information where conventional scientific data are lacking [27,28]. Individuals that are reliant on marine resources generally have higher levels of accumulated knowledge [29], which tends to be lost with increasing market integration and wealth [30]. Integrating LEK and conventional scientific knowledge to co-develop management strategies that fit coastal resource users’ needs remains a challenge but is essential to better transfer planning into action [31,32].

Rising to the challenge of biodiversity loss while meeting the needs of people requires us to think holistically about how we conduct conservation, not least by advancing social equity and including local perspectives and needs [33]. Viewing seagrass meadows as coupled social–ecological systems and incorporating LEK is instrumental; harnessing it remains a global challenge for seagrass conservation [25]. The present study aimed to investigate how individuals perceive and value seagrass meadows within the Indo-Pacific bioregion. We elicited LEK from five countries within the Indo-Pacific bioregion to understand the value that individuals place on seagrass habitats. Hence, we aimed to evaluate information on the loss of biodiversity, causes of decline, and how such losses are expected to impact people into the future in order to improve and strengthen the narrative.

2. Materials and Methods

2.1. Study Locations

The Indo-Pacific seagrass bioregion is the most diverse and abundant in terms of flora [11]. Seagrass meadows across the region are often the preferred habitat for fishing, with fishers targeting both finfish and invertebrates [10,24]. Between 2012 and 2017, we conducted household interviews within 150 coastal villages in areas across five countries (Cambodia, Indonesia, the Philippines, Sri Lanka, and Tanzania; Figure 1) within the Indo-Pacific seagrass bioregion where large proportions of society depend on marine resources for food security and livelihoods [20,24,34,35,36,37]. In our study, we considered a village as any human settlement or community unified by authority or local custom. To elicit local ecological knowledge, we employed a non-probability, convenience sampling design [38] whereby we selected villages in coastal areas where the use of marine resources for food security and livelihoods is high. We conducted interviews in the Kampot and Preah Sihanouk provinces of Cambodia, the Selayar and Wakatobi regencies of Indonesia, Puttalam Lagoon in Sri Lanka, the Western Visayas region of the Philippines, and the Mjini Magharibi and Unguja North regions of Tanzania. We selected areas within these countries that were in close proximity to seagrass meadows and other coastal habitats (coral reefs, mangroves, muddy substrates), and conducted interviews in a range of villages within these areas.

2.2. Household Survey

To understand how households perceive and value seagrass meadows within the Indo-Pacific bioregion, we used household surveys that were previously developed to understand coastal resource use patterns in the coral triangle [39]. These surveys made use of semi-structured interviews. Interviews were conducted in the local language via a trained interviewer and subsequently translated to English. We randomly selected households, largely from fishing villages, and interviews were conducted with household heads. We consider a household as a dwelling where one or more individuals live and share meals and a household head to be the individual who makes financial decisions. Firstly, the aims and objectives of the study were explained to respondents, before being asked if they would like to participate. All respondents provided verbal informed consent; written consent was not obtained because a verbal questionnaire was used. Moreover, large proportions of society in the study regions cannot read or write.

We utilised semi-structured interviews (Supplementary Materials) that lasted between 20 and 45 min, first collected information on demographics, e.g., [20], and followed with questions covering household socioeconomics and marine and coastal resource use (these data were not used within this study). Further questions were structured to elicit LEK on seagrass importance for food and fisheries, local changes to faunal communities and marine resource use patterns. We provided respondents with a number of statements, for which they could either agree, disagree, or state that they did not know. In Cambodia, households were only presented with two statements, and only households in Indonesia and Tanzania were asked about sea cucumbers. Ethical approval for working with human participants was obtained from Swansea University (SU-Ethics-Staff-250319/134).

3. Results

3.1. Demographics

In total, we interviewed the heads, or equivalent representatives, of 1327 households. Of these heads, 71% were male and 28% were female (gender was not recorded for 1%). Respondents ranged in age from 18 to over 71 years. Overall, 73% of respondents were between the ages of 30 and 60, followed by 16% between the ages of 18–30, and 11% above the age of 60. In total, 76% of respondents had lived in their village for more than 25 years or since birth, followed by a further 8% whom had lived there for 21–25 years.

3.2. LEK: Seagrass Importance for Food and Fisheries

Seagrass meadows were highlighted across all countries as an important place to find and collect food (86%, n = 1174) and only a small proportion of respondents disagreed (7%) or did not know (8%; Figure 2A), primarily driven by respondents in Sri Lanka (Figure 2B). Most respondents agreed that seagrass is very important to people (84%, n = 1171) and that seagrass meadows are an important habitat for the fish that they collected (89%, n = 1172). The vast majority of respondents (93%, n = 1253) agreed that damage to the marine ecosystems would make their lives more difficult in the future, and few respondents disagreed (3%) or were unsure (4%; Figure 2A). When compared with respondents in Indonesia, the Philippines, and Tanzania, Sri Lanka had a larger proportion of respondents that did not have knowledge of seagrass meadows (Figure 2B).

3.3. LEK: Changes to Faunal Communities

Most respondents perceived that there were fewer and smaller fish and invertebrates than there were five years ago (Figure 3). Overall, 79% of respondents stated that there was less fish and marine life than there was five years ago (n = 1226; Figure 3A); however 12% disagreed, primarily driven by respondents in Indonesia (15%) and the Philippines (12%; Figure 3B). In addition, 10% of respondents did not know if there were differences in the abundance of fish and marine life over a five-year period, primarily driven by respondents in Sri Lanka (35%). While there was a collective perception that fish were smaller than they were five years ago (71%, n = 1234), a number of respondents disagreed with this (18%) or did not know (12%). We found that responses were similar for shells (gastropods), where 62% agreed that they were smaller, 16% disagreed, and 21% did not know (n = 1031), as well as sea cucumbers, where 81% believed they were smaller (n = 791), 10% disagreed, and 9% did not know. We found that respondents in Sri Lanka were the most unsure about the size changes of fauna; 48% did not know if fish were smaller and 84% did not know if shells were smaller than they were five years ago.

3.4. LEK: Effects of Coastal Resource Use

An average of 77% percent of respondents (n = 1035) agreed that overfishing was a problem in their geographical setting (Figure 4A); however, this response varied by country (Figure 4B); in the Philippines, the majority of respondents disagreed (66%), whereas in Indonesia, the vast majority agreed (88%). When asked about gleaning, most respondents disagreed (54%, n = 1152) that gleaning was a threat to marine biodiversity (both seagrass flora and fauna). While 44% (n = 887) of respondents disagreed that seaweed farming impacted seagrass (Figure 4A), results were mixed at the county level (Figure 3B); respondents in Indonesia (63%) and the Philippines (61%) generally disagreed, but in Tanzania, respondents agreed (70%) that seaweed farming impacted seagrass. Respondents in Sri Lanka were unsure about both gleaning (66%) and seaweed farming (84%). While just over half of respondents seemed to agree that seagrass was being damaged (51%, n = 1177), the majority believed that seagrass would persist forever (71%, n = 1174).

4. Discussion

By engaging with local stakeholders from five countries across the Indo-Pacific region, local ecological knowledge (LEK) provided a narrative of the importance of seagrass meadows to people, particularly as a place to find and collect food. This study only focused on the provision of food security and livelihoods, but seagrass meadows are important for many other ecosystem services vital to humanity [40], such as their role as blue carbon habitats. While policies are advancing that recognise seagrass meadows as blue carbon habitats, the provisioning services that seagrass meadows provide are of primary importance at the household level [41].

In the present study, we report ecological changes that were perceived locally over a five-year period. Declines in the number and size of both fish and invertebrates were reported in all areas, all of which are locations with little to no formal fisheries landings data (particularly for invertebrates), an issue across much of the Indo-Pacific region [42]. LEK from the region demonstrated an acute awareness of how damage to marine ecosystems is impacting people now and in the future. However, our study exposed the dynamic nature of LEK, revealing how external forces and behaviours (e.g., personal opinions and responsibilities) may result in cognitive dissonance, and the motivated reasoning that hybridises LEK. We showed that despite acknowledging that seagrass was threatened, and that local biodiversity had declined in number and size, respondents perceived that activities they conducted, gleaning for example, were not a threat and that seagrass would persist into the future—statements not supported by conventional scientific knowledge (CSK). It is therefore critical to integrate data from different knowledge bases when communicating and engaging with stakeholders to manage resources sustainably.

Our study builds on previous work in the region showcasing the value of seagrass to people, notably as a place to find and collect food [10,20,21,43,44,45,46], and an often-overlooked contribution to household food security that households are willing to pay to protect [47]. We found that the vast majority of respondents were aware of the important habitat role that seagrass meadows play for fish—knowledge likely driven by their dependence on the habitats for fishing, e.g., [27,48].

Across countries, respondents indicated that fauna had reduced in both number and size over a five-year period. Size-based indicators of faunal communities are useful as they represent the distribution and flow of energy within ecosystems [49,50] and the changes we report here could indicate two things. Firstly, these changes (fish size decline) are mirrored in other habitats, where studies reveal that fishing can directly change the size distribution of fish communities through the over-harvesting of large individuals, which indirectly increases the abundance of small individuals due to a lack of predation [51,52]. However, changes to fish size could also be an artefact of changes to the fishing habitat and could suggest that seagrass fisheries, where juvenile fish are much more common, play an increasingly important role, e.g., [15]. Organisms harvested through gleaning (gastropods and sea cucumbers) were reported to demonstrate similar declines in size. This conforms with previous studies from the region [53], where changes were attributed to the increasing number of harvesters and a change in personal behaviour; where once gleaners would look for large individuals (and leave younger individuals to mature), changes in local abundance resulted in gleaners collecting everything that they found to ensure a worthwhile catch. Respondents in Sri Lanka had much less knowledge of changes to the size distribution of gastropods than other countries, suggesting that gleaning may not be an important activity in the region the study was conducted in (Puttalam Lagoon, Sri Lanka).

While the majority of respondents were acutely aware that overfishing was a problem, and likely associated this with the decline in the number and size of fish, when it came to gleaning activities, most households disagreed. This could be explained using Attribution theory [54], which incorporates cognitive dissonance and motivated reasoning to understand how perceptions influence the attribution of causes to occurrences [55]. Cognitive dissonance is a psychological trait where contradicting cognitions (previous knowledge or thoughts) provide a basis to acquire or invent new beliefs that reduce the amount of cognitive dissonance (internal mental conflict) between cognitions [56,57]. Since the creation of LEK can be a cognitive process, individuals may use past experiences and events to inform current beliefs. CSK has identified that unregulated gleaning can significantly impact the abundance and size of invertebrates, e.g., [53,58,59], but it may be that previous experience (i.e., the community have always gleaned like this) potentially causes individuals to believe that their actions cannot be the cause of decline (i.e., it must be something or someone else).

In a similar vein, motivated reasoning [60] provides insight into how motivation influences beliefs. Here, the belief that gleaning and seaweed farming are not a threat, and that seagrass will persist forever are potentially motivated by the values that the activities and habitat provide (e.g., food and income). Motivated reasoning posits that individuals are motivated to selectively use prior knowledge, in this case the value of seagrass as a place to collect and find food, or a substrate for seaweed farming, to support the pre-desired conclusion that seagrass will be here forever. Despite the observed seagrass decline across the region, e.g., [12], and CSK identifying gleaning and seaweed farming as threats [16], individuals are potentially motivated to believe that seagrass will exist forever because they depend on it so greatly. These findings somewhat contrast with other studies from the region; studies from Kenya and Indonesia reveal gleaners’ knowledge of seagrass decline and how this decline is linked to invertebrate catches [43,61]. However, when it came to seaweed farming, we found a mismatch between countries; respondents in Indonesia and the Philippines disagreed that seaweed farming was a threat to seagrass, whereas those in Tanzania agreed. Other studies from Tanzania reveal that seaweed farmers were acutely aware that their activity threatens seagrass [62,63], but in Indonesia, seaweed farmers perceive there to be no link between environmental quality and seaweed farming [64]. This potentially suggests that there are more complex issues at play. While our findings establish a narrative of biodiversity loss, they reveal the variability in human perceptions of the environment and an individual’s responsibility in this which may link to shifting baseline syndrome [65]. The farming of seaweed began much more recently in Tanzania (1989 onwards) than it did in the Philippines (1969 onwards) [66]; and the loss of seagrass due to the practice may be in recent memory in Tanzania.

While CSK is useful for understanding the ecological or economic values of habitats such as seagrass, LEK reveals values that have been firmly established over time. Differences between LEK and CSK are not uncommon, even though there are synergies between the two [67]. In general, LEK is useful to record historical change and the factors that local communities attribute to change may overlooked by scientists [25]. The contrasting cognitions and motivated reasoning we discuss above suggest that the values associated to seagrass meadows (e.g., a place to find food, important for people and fish) are deep-rooted and have transcended generations. However, these psychological processes may weaken livelihood resilience in the future if they are not confronted, making individuals susceptible to socioeconomic and environmental changes that may force them to further degrade the environment on which they depend. Rising to the challenge of biodiversity loss requires holistic management solutions that marry LEK and CSK [67], and incorporating the two has been recommended in both terrestrial and marine systems [48,67,68]. This need is the greatest in cases where cognitive processes result in differences between LEK and CSK, since personality traits can alter the adoption of conservation or management innovations [69]. Ignoring LEK may therefore serve to place resources and resource-users at greater risk [70]. In Fiji, for example, an increasing number of gleaners led to smaller sized invertebrates being landed and a shifting baseline of population size that resulted in overfishing [71]. Moreover, the inclusion of LEK in management or development is fundamental to recognise the rights of local and indigenous people and to avoid environmental injustice [72].

We know that seagrass meadows are in decline across the entire Indo-Pacific seagrass bioregion [12], with changes associated to multiple factors including overfishing, coastal development, and eutrophication [18]. Rarely is LEK included in seagrass conservation, and while CSK is useful to inform policy, local communities are responsible for political influence. In light of this, we support recent policy recommendations made for seagrass ecosystems within Pacific Island countries and territories [73], which are applicable to the entire Indo-Pacific region. These recommendations broadly focus on increasing local stewardship through developing scientific literacy and awareness of threats, co-producing knowledge and management actions that integrate rights and local resource use, and supporting the valuation of seagrass ecosystems in terms of their socio-economic and cultural contributions to people.

5. Conclusions

Individuals use and value the marine environment for many different reasons. In conclusion, local ecological knowledge demonstrated the importance of seagrass meadows as a place to find and collect food—knowledge that was present across the entire Indo-Pacific region, revealing it to be widespread. We found that individuals were knowledgeable that seagrass was important for fish species and that damage to the marine environment would negatively affect them in the future. Local ecological knowledge from this study also established biodiversity declines in areas where we lack long-term monitoring data. This showcases the value of LEK for long-term monitoring for natural resource management. However, our study also demonstrated the complex nature of local ecological knowledge and how cognitive processes can influence past, current, and future knowledge. This study highlights the importance of using LEK so that shared values can be incorporated into management but also stresses the need to pair LEK with CSK for validation, especially in the case of contrasting cognitions.