Land crabs Gecarcoidea lalandii is considered a tropic factor sustaining the food web in marine-mountain ecosystem and a valuable source for tourism and livelihood development. Land crab life’s cycle depends on both forest and tidal so their natural populations are used as indicators for the linkage between forest and marine ecosystems health.
Based on local ecological knowledge from the Cu Lao Cham residents, G. Lalandii is a nocturnal species. Their habitat perimeter extends between 1 to 12 meters around their cave with density of several hundred crabs per cave . Land crab population size on Cham islands varies between 30,000 and 35,000 individuals , , , , . Their main food sources consist of vegetables, forest leaves, worms, and dead animals. The breeding season of G. Lalandii occurs between June and September   . Measurement data gathered by community shows that land crabs carrying eggs have a size varying between 40 to 78 mm, with the highest frequency around 60mm , . The breeding process entails the nocturnal migration of female crabs from their caves to tidal areas. Female crabs use their pincers to remove the eggs and release them in the sea. This process is very fast, varying from 5 to 10 mins, after which they quickly return to their forest caves . The larvae spend an average of 7 to 10 days developing into juvenile during which they change their shell several times. Juveniles crawl to the shore and live near the water’s edge until they have relatively grown up and migrate into the forest where they live until maturity and only return to sea for spawning by which they complete their lifecycle.
Attempt for solutions have been offered and implemented by government, scientist, private sector and local communities. As a result of this cooperation, a local team was formed to implement this special model. The stakeholders have been created the criteria, indicators and parameter in operation of this model. These include areas, seasonality, individual size, reproduction patterns, and eco-labeling.
Ecological significance of land crab population on Cham Islands
Land crabs are extremely important for the ecosystem in general and in particular for forest ecosystems. They help transfer the energy flow from land into the sea and back, promote the biogeochemical cycle by consuming falling objects in the forest litter, reduce erosion, activate the soil structure and improve groundwater resources. In addition, land crabs have a positive role in seed dispersal and enhancing flora biodiversity of the rainforest  Thus, the evolution of land crab population will reflect the situation and health of forest ecosystems on Cham Islands.
Community understanding of biological and ecological characteristics of the land crab
From different thinking and understanding of land crab life, researches on Cham Islands have added scientific information for local people for understanding on: where land crabs live, what their ecological environment is, what their food source is, what its life cycle is, how to protect the land crab population in the wild. These issues are used as a basis to attract local people to become involved in land crab conservation and sustainable development processes focusing on their sustainable livelihoods.
Land crab resources situation, management, exploitation and conservation
Analysis shows that in 2000 land crabs were caught on the islands only accidently and were limitedly used for consumption or as gifts for relationships on the mainland. In 2006, the MPA was established and visitors began to come to the islands. As results land crab consumption and associated land crab cultivation jobs were created. In 2009, Cham Island became the core zone of the Cu Lao Cham – Hoi An Biosphere Reserve, the number of tourists increased quickly thereby increasing the land crab use demand. Subsequently, the amount of people exploiting land crabs, mining time, frequency, crab size decreased, and exploitation area increased, crab size decreased. Development on Cham Island resulted in the construction of a road circling Hon Lao Island. Both the construction process and the road itself are perceived to impact the ecosystems health in general and in specific fauna and flora species; limiting the availability of food for the land crab population on Cham Island.
Exploitation and consumption activities of land crabs on Cham Island were limited in 2009 by Directive No. 04/2009-CT on September 20 by the Hoi An People’s Committee. Analysis shows that this prohibition was not a perfect solution to protect the land crab. As tourism demands continued to rise, people continued to illegally exploit land crabs. Enforcement of this Directive was problematic and ineffective. This resulted in conflicts between community members, tourists, the government and continued until a harmonious balance between exploitation and conservation was suggested by the project “Community participation in natural recovery and conservation of land crab on Cham Islands” by Global Environment Facility (GEF). This project received agreement from the Government and has been implemented as a pilot since 2011.
The management process based on size, time, status, eggs carrying, eco-labeling does not only allow exploitation and local livelihood development; it also supports a natural conservation mission.
Establishment and implementation of the land crab exploitation and protection team
The exploitation and protection land crab team was established in 2012 and consisted of 18 members who are professional exploiters. The membership was expanded to 33 members in 2016 and now has more than 40 members. The team installed regulations, monthly-yearly quota and the price of land crab. Indicators for land crabs are developed and include size, male/female rate, carrying eggs status, and eco-labeling.
These indicators and the enforcement are the result of cooperation between the farmers union, the Hoi An city government and local people. Furthermore, members also coordinate with the relevant authorities concerning the protection and development of the land crab population in nature.
Creating the land crab catch management indicators 
The criteria developed and applied for land crab exploitation on Cham islands are:
(i) Catch, sale, use time allowed: 01st of March to 31st of July.
(ii) The land crab catch quota: based on the current situation of land crab population from scientific information, local people and government agencies discuss and set the land crab catch monthly and yearly quota. The quota is around 10,000 crabs per year since 2012.
(iii) Land crab catch size allowed: Larger than 7 cm of carapace.
(iv) Carrying eggs status: it is not allowed to catch female crabs carrying eggs.
(v) Price: Fixed price is valid for one year.
(vi) Eco-labeling: All legally exploited land crabs are eco-labeled before sale.
Promoting the four forces combination in land crab catching management process
Although land crab exploitation management processes have been applied, many difficulties and conflicts remain. Enforcement of regulations and controlling exploiters has been shown very difficult to manage. People who are not members of the land crab exploitation team continue to illegally exploit.
Analysis shows that this prohibition was not a perfect solution to protect the land crab on Cham Islands . After 3 years, it has operated quite effectively, the exploitation, sale and use of land crab at Cham Islands has come into shape; the management is based on scientific information and participation, and ownership is given to the societal partners but challenges and conflicts have also arisen. Members have been reported to transfer eco-labels without the authorities’s approval. The activities of the interdisciplinary inspection team are difficult and have been considered inefficient .
To resolve these issues the four forces cooperation mechanism for land crab management processes is proposed. This mechanism comprises the following targets; stakeholder participation, creating coherence and close coordination between stakeholders, creating mutual control between parties, reducing management burdens for authorities, promoting internal resources and strengths of the parties and creating mechanisms to divide responsibilities in managing and reducing risks for resource conservation. In addition to the benefits mentioned above, a cost-benefit comparison has been calculated as follows:The funding to conserve land crab on the islands amounts to around 1.367 billion Vietnam Dong (VND). This amount is used as a baseline to compare the cost benefit and profit ratio between the traditional and the 4 forces combination model in land crab management process.
The application of the 4 forces combination in land crab management and development has showed a higher significance in biosphere reserve.
Land crabs play a very important role in people’s lives on Cham Islands. They are stimulating for tourism development and as biological indicators to monitor the forest ecosystems health. Population size and distribution of land crabs depend on coverage and forest vegetation quality. In the life cycle, land crabs need forests for habitat and food, and tidal areas to spawn.
Increasing construction on the islands is impacting the life cycle; making the living space segmented, reducing water resources, decreasing food sources, increasing barriers on the spawning migration path.
To ensure economic development and national security the migration path, eco-region and food resources should be maintained and protected. These issues require the participation of stakeholders to discuss and solve issues in scientific and local practical conditions to improve the land crab population viability. The analysis yielded results on 5 levels: (1) awareness raising, (2) habitat and nutrition preservation, (3) migration path protection, (4) spawning ground protection, (5) human-nature conflict reduction and the four forces combination effectiveness enhancement.
This model highlights that the need to conserve the land crab in conjunction with sustaining local livelihood. A set of criteria/indicators for exploiting and controlling the crab and monitoring team have been set up by agreed stakeholders under the regulation of local authority. In order to implement effectively the initiative, we argue that the process should be participated by four forces including local government, scientists, entrepreneurs and farmers. Obviously the tourism would be benefits from UNESCO biosphere reserves, but consumption demand from tourists should be responded positively from local governance to meet the harmonizing three functions of biosphere reserves, i.e. conservation, development and logistic support.
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