Course:FRST370/The Mangrove Ecosystem, Ucides cordatus, and the Local Economy in the Caeté Estuary, Northern Brazil

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This study investigates the mangrove ecosystem of the Caeté Estuary in Northern Brazil. It explores the complexity of the ecosystem, the local populations' primary food resource – the mangrove crab (Ucides cordatus), and economic issues arising from environmental degradation. Analysis of stakeholders and joint efforts to curtail the damaging processes, or lack of, are also examined The crab inhabits the high intertidal mangrove forest, which is composed of four mangrove species, with Rhizophora mangle being the dominant. Forest management of the estuary is a prevailing driver for the sustainability of the crab population; however, that crab population has become increasingly susceptible to over fishing and wastewater discharge from nearby communities.

Description of the Case Study

R. mangle forest in the estuary

Location and Size

The case study is set in the mangrove ecosystem of the Caeté estuary in Northeast Brazil. The estuary spans ~100 km along the northeast coast of Pará state and is located at the mouth of the Caeté River, a tributary of the Amazon River (Lima et al., 2019, pp. 2[1]). The Caeté estuary is part of a joint estuary marine conservation unit, forming the southeast portion of the mangrove Bragança peninsula, with the Taperçu estuary forming the Northwest portion (Lima et al., 2019, pp. 2[1]). Together, they share an area of 41,807 ha (Unidades de Conservação, n.d.[2]), with the Caeté estuary constituting ~32,000 ha (Lima et al., 2019, pp. 2[1]), with the estuary land base occupied by mangrove forests spanning ~20,000 ha (Diele et al., 2010, pp. 2[3]). The two nearest municipalities are Augusto Corrêa and Bragança, with the former being ~10 km southeast of the estuary and the latter located ~20 km southwest of the estuary. The communities are inhabited by 40,497 and 113,227 people, respectively, and combine for ~153,724 as of 2010 (City Population, 2019[4]).

History, Ecosystem, and Importance

A typical U. cordatus crab

Caeté estuary is home to ~3000 people and was formed in 2005 under federal jurisdiction for the sustainability and conservation purposes in light of its ecological biodiversity and economic reliance by local communities (Unidades de Conservação, n.d.[2]). The estuary belongs to the world’s second largest mangrove belt and supports a complex ecosystem of monkeys, hawks, raccoons, shrimps, 4 mangrove trees species, and 29 terrestrial and aquatic crab species (Berger et al., 1999, pp. 125[5]; Diele et al., 2010, pp. 252[3]; Koch & Wolf, 2002, pp. 127[6]). Among the biodiversity, Rhizophora mangle is the dominant mangrove species and the most exploited crab is Ucides cordatus (Diele et al., 2010, pp. 6[3]). R. mangle leaves have high carbon and nitrogen ratios and high tannin and lignin concentrations, offering minimal nutrition and rendering them relatively hard to digest. However, the leaves make the ideal food source for the U. cordatus because of their low metabolism rate (Koch & Wolf, 2002, pp. 127[6]). Due to the low presence of consumers capable of digesting the leaves, it would be common for the mangrove leaves to be transported out of the ecosystem via ocean tides. However, the ability of U. cordatus to digest the leaves prevents the nutrients and energy from escaping the ecosystem by increases the detritus material available for microbes to decompose and return to the soil (Koch & Wolf, 2002, pp. 127[6]). In return, R. mangle roots provide the ideal shelter from predators, including humans. With the addition of decomposers, the three groups (mangroves, crabs, and bacteria) establish a positive feedback loop within the ecosystem, where the benefit to one group positively influences the others (Koch & Wolf, 2002, pp. 127[6]).

U. cordatus is the most abundant and edible food source in the area, constituting up to ~1500 tonnes/year (Koch & Wolf, 2002, pp. 127[6]). With the exception of humans, the abundance of U. cordatus is attributed to the low presence of predators (raccoons, monkeys, hawks, etc.), enabling the species to thrive (Koch & Wolf, 2002, pp. 127[6]). The species is heavily depended upon, with 42% of local households collecting and selling the crap and generating 38% of household income (Koch & Wolf, 2002, pp. 120[6]). Although currently tolerable, increasing trends in agriculture, overfishing, tourism, urbanization, and wastewater discharge, and illegal deforestation are leading factors in habitat and environmental degradation (Berger et al., 1999[5], pp. 131; Koch & Wolf, 2002, pp. 120[6]). This has led to friction between communities and corporations. This case study will investigate any tenure and administrative agreements, analyse any stakeholders and joint efforts to curtail the damaging processes or lack of, assess its governance, and explore recommendations.

Tenure Arrangements

Up until 2005, the local people possessed only customary rights to the land, and the land was de facto open-access (Glaser, 2003, pp. 268[7]; Diele, Koch, & Saint-Paul, 2005, pp. 169[8]). However, a proposed co-management plan for the Caeté estuary changed the area from de facto open-access to common property management (Diele, Koch, & Saint-Paul, 2005, pp. 176[8]). The extractive reserve (RESEX) program was introduced in order to give local people the right to exclude outsiders from the extraction of mangrove products and implement harvesting rules (Glaser & Oliveira, 2004, pp. 224[9]). However, some of the rights of the local people are in conflict with environmental legislation in place (Glaser & Oliveira, 2004, pp. 224[9]).

Administrative Arrangements

Many people currently living in the communities originated elsewhere, indicating heavy immigration pressures (Diele, Koch, & Saint-Paul, 2005, pp. 170[8]). This has been the root of resource conflicts in the Caeté estuary, as the local people hold customary rights to the land, but the territories are not enforced by law and local people have no means to enforce it themselves (Glaser, 2003, pp. 268[7]). This has essentially led to de facto open-access exploitation of the mangrove system (Diele, Koch, & Saint-Paul, 2005, pp. 169[8]). While the government has no authority or enforcement presence in the estuary, it has implemented harvesting rules for the U. cordatus. These laws ban the capture of female crabs from December to May, while male capture is banned for several days during mass-mating events; they also ban the capture of crabs with a carapace size under 6 cm (Diele, Koch, & Saint-Paul, 2005, pp. 170[8]). Despite the regulations restricting crab harvest, the crab fishermen are often unaware of the laws and harvest anyway; demonstrating the absence of government influence (Diele, Koch, & Saint-Paul, 2005, pp. 176). Although the crab fishermen are unaware of government laws, they do follow their own unwritten harvesting rules that have come from both market-pressures and tradition. Crab harvesters do not capture females out of fear of population extinction (Diele, Koch, & Saint-Paul, 2005, pp. 176[8]). Furthermore, there is local opposition to diminish mesh net sizes and several fishing practices that are considered predatory (Glaser, 2003, pp. 268[7]). This shows that even in the absence of government-enforced harvest laws, local crab harvesters are capable of creating their own through the traditional knowledge of sustaining crab supply for the benefit of all livelihoods and avoiding the all-too-familiar sustainability problem - the tragedy of the commons (Hardin, 1968, pp. 1245[10]).

Social Actors

Affected Stakeholders

The local communities who live in the Caeté estuary both require the estuary for subsistence and their livelihoods (Glaser, 2003, pp. 266[7]). Surveys revealed that 80% of local people live on mangrove products, while 68% obtain income from the mangrove estuary (Berger et al., 1999, pp. 125[5]). The poorer community households rely heavily on collecting firewood and food from the mangrove forest; they are dependent on collecting these products for subsistence instead of supporting their livelihood, seen through the low market value of the products collected (Glaser, 2003, pp. 267[7]). However, most community households in the Caeté estuary support their livelihoods through mangrove products, with the most lucratively harvested being the Ucides cordatus. Most locals within the communities hold customary rights; however, the diminishing catch sizes have led to user conflicts and territorial disputes as collector groups have started to impede on other’s customary territories (Glaser, 2003, pp. 268[7]). Due to there being no present governing power over the territorial claims, there are no laws protecting local communities' customary lands. While local men dominate crab harvesting, the women mostly process crab meat and poorer household women collect subsistence materials (Glaser, 2003, pp. 267[7]). The whole household is usually involved in some form of crab harvesting and processing endeavors.

Other affected stakeholders are trade intermediaries of the U. cordatus market chains. The crabs are sold live or processed at markets; these market chains often contain intermediaries (Nascimento et al., 2017, pp. 44[11]). While the intermediaries do not rely on the mangrove system for subsistence, they do rely on the mangroves through the crab harvesters for their livelihoods. The intermediaries’ jobs are often based on reciprocity and verbal agreements with the fishermen; the intermediaries are often not held to the same restrictions as the fishermen because the government harvesting restrictions do not apply (Nascimento et al., 2017, pp. 44[11]). There is a mutually beneficial relationship between crab harvesters and trade intermediaries. The intermediaries rely on the crab harvesters for their supply and livelihoods, while the crab harvesters rely on intermediaries to provide the secure sale of the crabs, allowing them to focus on harvesting; intermediaries also buffer fishermen from the variability of the production volumes of crabs (Nascimento et al., 2017, pp. 45[11]). However, there is an imbalance of power due to the low socio-economic standing of the crab harvesters; the fishermen are often dependent on intermediaries for monetary loans, which leads to an increase in loyalty and a constant influx of crabs for the intermediaries (Nascimento et al., 2017, pp. 48[11]). The loans have no grace period or interest and are based purely on mutual confidence (Nascimento et al., 2017, pp. 49[11]). While there is a power imbalance in the relationship between intermediaries and harvesters, they are often both still reliant on each other for their livelihoods.

Interested Outside Stakeholders

One of the interested stakeholders of the Caeté estuary is the government. In an attempt to preserve the ecology of the mangrove system, the government imposed harvesting rules for the local communities. However, their relative power over the Caeté estuary is quite minimal; due to the scarce human and financial resources of government officials, their ability to enforce regulatory measures is limited (Glaser, 2003, pp. 265[7]). This lack of presence has led to communities being uninformed, alienated, and uninvolved with government officials and their attempts to manage natural resources (Glaser, 2003, pp. 265[7]). The government’s main objective with regard to the Caeté estuary is to protect its ecology; however, their power is relatively low in the area.

Other interested stakeholders are the markets and buyers of U. cordatus. The markets and buyers are not dependent on U. cordatus for their livelihood or subsistence; however, they do play a key role in the drive for harvest. The markets and buyers not only push the economic incentive to harvest crabs, but also drive the size of crab captured (Diele, Koch, & Saint-Paul, 2005, pp. 176[8]; Glaser, 2003, pp. 268[7]). The selective pressure of fisheries for large males has both a commercial and traditional background; due to intense market-control, the Caeté estuary fishermen and consumers consider larger than legal size crabs to be the market size (Diele, Koch, & Saint-Paul, 2005, pp. 176[8]). The mean catch of crabs is 7.4 cm for the carapace, while the legal minimum requirement is 6 cm (Diele, Koch, & Saint-Paul, 2005, pp. 176[8]). Even though the catch per unit of effort (CPUE) increased 15% from 1997-2003, the crab harvesters have not counteracted this through harvesting smaller crabs; this is evidence of the power the market has over the harvest (Diele, Koch, & Saint-Paul, 2005, pp. 177[8]).


There are plans to implement a co-management agreement in the Caeté estuary that would establish the area for common property management (Diele, Koch, & Saint-Paul, 2005, pp. 177[8]). While the RESEX program was started in 2005, our assessment outlines the improvements social actors should apply to succeed within their co-management practice (Dartmouth, 2019[12]).

Government Influence

As Glaser (2003) explained, there are several reasons why natural resource management implementation has failed. First, government officials have a limited ability to enforce regulatory measures due to sparse human and financial capital; this leads to communities being uninformed, alienated, and uninvolved with the government’s attempts to manage natural resources in the area (Glaser, 2003, pp. 265[7]). Second, until the 1990s, management practices neglected the role local people took in the management of resources; this neglect led to resistance by local stakeholders to implement plans (Glaser, 2003, pp. 266[7]). Third, the attempts of resource management implementation lacked stakeholder analysis and participatory rural appraisal (Glaser, 2003, pp. 266[7]). Finally, there is a lack of attention to local social sustainable priorities (Glaser, 2003, pp. 266[7]).

Social Welfare

A major issue in the communities is the lack of social infrastructure and the low socio-economic standing of the community members. Mangrove crab harvesters are often socio-economically marginalized, live in poor infrastructure houses with little hygiene, and are illiterate or functionally-illiterate (Nascimento et al., 2017, pp. 45[11]). The people are not living in great conditions with a lack of a basic drainage system and often have harmful bacteria, such as fecal coliform, present in their water supply; furthermore, commercial, domestic, and medical waste are often discharged in larger towns upriver (Guimarães et al., 2009, pp. 1220[13]). Moreover, roughly half of the villages in the Caeté estuary have electricity and medical care, and only a few villages have piped water (Glaser, 2003, pp. 269[7]). One can see how the lack of social infrastructure can often take priority over sustainable natural resource management practices.

Another issue facing the communities of the Caeté estuary is the lack of occupational options for both men and women. There is a low quality of education and schools past primary school are often hard to reach in these rural areas; children often do not learn to read or write (Glaser, 2003, pp. 270[7]). This often limits the options available to the people living in the Caeté estuary, offering few opportunities to do something other than crab harvesting. Out of 80 interviewees that Glaser conducted in the Caeté estuary, none of the crab collectors wanted to pass down their jobs to their sons, despite most of the sons joining the occupation (Glaser, 2003, pp. 270[7]). Additionally, women often do not have occupational options, other than crab processing and collection of subsistence products (Glaser, 2003, pp. 270[7]). This coupled with the immigration pressures could lead to more pressures on the collection of marketable U. cordatus.

Immigrant Influx

Immigration is a large issue in the Caeté estuary region. More people living in an infrastructural-deficit region has led to more issues. In the Caeté estuary region, 44% were born outside their rural communities, which indicates immigration pressures (Glaser, 2003, pp. 267[7]). From 1996 to 1998, the crab collectors increased by 20%; this expansion of collectors in combination with de-facto open access has resulted in the development of more aggressive fishery methods (Glaser, 2003, pp. 268[7]). Contemporary crab harvest has expanded to the entire estuary and is done by employee groups with powered boats; these methods contradict the more selective, traditional methods and could explain why the male crab size is decreasing (Diele, 2000, pp. 54[14]; Diele, Koch, & Saint-Paul, 2005, pp. 176[8]). The diminishing catch size has resulted in user conflicts and territorial disputes as collector groups start to impede on other’s customary territories (Glaser, 2003, pp. 268[7]). While the male capture size decrease has not affected its biological viability, it has affected its commercial viability due to it being below the size of commercial interest (Glaser, 2003, pp. 268[7]; Diele, Koch, & Saint-Paul, 2005, pp. 176[8]).


It can be deduced that the trade intermediaries have the power over the crab harvesters, while the market has the most power over the actions of the affected stakeholders. As noted above, the crab harvester’s loyalty is held to the intermediaries through verbal agreements, reciprocity, and financial loans (Nascimento et al., 2017, pp. 49[11]). These loans often take away the crab harvester’s freedom to sell their crabs to anyone else and this exacerbates the inequality of power. Nonetheless, the market has the greatest power of them all. It drives the minimum size of crabs caught above the governmental limits (Diele, Koch, & Saint-Paul, 2005, pp. 176[8]). On the other hand, the government does not have much power due to them lacking financial and human capital to enforce regulations (Glaser, 2003, pp. 265[7]).


The extractive reserve (RESEX) program was implemented in the Caeté estuary in 2005 for the conservation of natural resources traditionally used by local communities (Dartmouth, 2019[12]). However, the influx of immigrants due to Amazonian deforestation and the absence of government enforcement has had minor sustainable success over the past 20 years (Dartmouth, 2019[12]). There are a number of recommendations for moving towards more sustainable conservation that will ensure the continuation of its resources while improving local livelihoods. One recommendation is for local communities to appeal to the Brazilian government for the recognition of legal customary rights to the land, enabling the communities to have legal authority over the land and its natural resources. The legal enforcement of communal roles could pave the way for better joint management between small local harvesters and large scale group harvesters (Nascimento et al., 2017, pp. 50[11]). Furthermore, crab harvesters should include intermediaries in the decision-making process for sustainable management strategies (Nascimento et al., 2017, pp. 50[11]). Similar to the case study of Naidu villagers in China (Menzies, 2007, pp. 21[15]), the Caeté estuary villagers and surrounding communities could benefit from organizing into groups and implementing communal harvesting rules in an effort to strengthen social interactions (Nascimento et al., 2017, pp. 50[11]). The restructuring of the existing management framework between intermediaries and crab harvesters could establish a more systematic operation, with crab harvesters driving for social and ecological function, and intermediaries assuming a sales representative role and driving for economic function (Nascimento et al., 2017, pp. 50[11]). Furthermore, the intermediaries could network with research groups, NGOs, universities, and environmental groups, potentially unlocking funding opportunities, stewardship and enforcement through educational means, storage and transportation options, etc (Nascimento et al., 2017, pp. 50[11]).


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This conservation resource was created by Rebecca Brooks and JP Deland. It is shared under a CC-BY 4.0 International License.