Safeguarding the Underwater Cultural Heritage of Stone Tidal Weirs on the Earth

A. Iwabuchi
Published: 22 September 2021
Last edited: 22 September 2021
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Stone tidal weirs are a type of fish barrier operated by tidal amplitude.  These structures are made of large rocks, extending along the shoreline on a colossal scale in semicircular, arrow-like, or almost linear shape. These weirs are completely submerged during high tide, and they emerge into full view at low tide, allowing people collect fish.

They are located within seascapes created and maintained by the harmonious interactions between humans and marine ecosystems.  Although they are on the verge of disappearance because of costal developments and global climate change, their role as eco-friendly fishing gear, womb for sustaining marine biodiversity, and tourist attraction has started attracting international attention.

This solution focuses on the cooperation established by universities and coastal communities to raise awareness on the role of stone tidal weirs and the connected traditional ecological knowledge of coastal communities as the cultural heritage.


East Asia
East and South Africa
North America
Southeast Asia
West Asia, Middle East
West and South Europe
Scale of implementation
Coral reef
Marine and coastal ecosystems
Rocky reef / Rocky shore
Biodiversity mainstreaming
Coastal and marine spatial management
Fisheries and aquaculture
Health and human wellbeing
Indigenous people
Legal & policy frameworks
Local actors
Science and research
Traditional knowledge
Loss of Biodiversity
Ocean warming and acidification
Sea level rise
Tropical cyclones / Typhoons
Tsunami/tidal wave
Ecosystem loss
Pollution (incl. eutrophication and litter)
Unsustainable harvesting incl. Overfishing
Changes in socio-cultural context
Lack of public and decision maker’s awareness
Sustainable development goals
SDG 3 – Good health and well-being
SDG 11 – Sustainable cities and communities
SDG 13 – Climate action
SDG 14 – Life below water
Aichi targets
Target 1: Awareness of biodiversity increased
Target 2: Biodiversity values integrated
Target 6: Sustainable management of aquatic living resources
Target 7: Sustainable agriculture, aquaculture and forestry
Target 8: Pollution reduced
Target 10: Ecosystems vulnerable to climate change
Target 15: Ecosystem restoration and resilience
Target 18: Traditional knowledge
Business engagement approach
Indirect through government


South Korea
People's Republic of China
East Timor
Federated States of Micronesia
Tahiti, French Polynesia
Solomon Islands
Papua New Guinea
United States
South Africa
United Kingdom


  • Environmental challenges: need to assess the impact of ocean climate change on stone tidal weirs, and their connected marine ecosystems. Today, some weirs only catch plastic debris from nearby towns.
  • Cultural and social challenges: stone tidal weirs should be designated by local and national governments and recognize in policy as underwater cultural heritage.
  • Economic challenges: need to balance stone tidal weirs and modern coastal developments. Stone tidal weirs have the potential to support healthy coastal communities and marine environments.


The main beneficiaries of this solution are coastal communities including local NGOs and NPOs, local and national governments, maritime anthropologists and archaeologists, as well as international organizations such as the UN, UNESCO, or ICOMOS.


How do the building blocks interact?

Under the framework of the UNESCO Convention on the Protection of the Underwater Cultural Heritage, international organizations such as UNESCO, the UNESCO UNITWIN Network for Underwater Archaeology, and ICOMOS-ICUCH have to raise awareness of stone tidal weirs as underwater cultural heritage and in supporting marine biodiversity.  This also includes raising the awareness of policy makers in countries that have not ratified the Convention, as well as continuing to provide high-level academic research upon stone tidal weirs on the basis of the international network. 

The solution focuses on fostering the traditional ecological knowledge of coastal communities, including the contribution of such knowledge and stone tidal weirs in biodiversity conservation, and on assessing the impact of the global climate change.  At local level, stone tidal weirs are abandoned when indigenous communities or community-based movements lose their interests in the heritage.  In many places, therefore, NGOs or NPOs organized by local communities and stakeholders are active for safeguarding or reviving stone tidal weirs; academics could mediate between international organizations and them.


This solution focuses on the work done in fostering the inclusion of coastal communities, as well as local and national governments, in the safeguarding and conservation of stone tidal weirs. 

  • Environmental: the management and protection of the underwater cultural heritage of stone tidal weirs are directly interconnected with the traditional ecological knowledge and customs of coastal communities. In addition, this cultural heritage along the shore is more vulnerable against climate changes such as sea level rise or destructive storms.
  • Cultural and social: in several places, community-based movements of restoring or rebuilding stone tidal weirs have already begun.  Researchers, anthropologists and archaeologists, are working together with the coastal communities that use the stone tidal weir as a site of research and environmental education for younger generations.
  • Health: fresh and free catches from stone tidal weirs have improved community health, since higher-nutrient fish has contributed to the well-being of people, including lower child mortality, improved cognitive performance, and strengthened immune function.
  • Economic: tourism around stone tidal weirs could play in raising awareness with the wider public.


Shiraho Conservation Council for Bountiful Seas

Shiraho hamlet on Ishigaki island (Ryukyu archipelago, Japan) used to have more than 10 stone tidal weirs, but by the end of the 1960s the last one was abandoned, simply because it did not manage to catch fish as much as in older times, being easily broken by typhoons or heavy waves.

In 2005, the NGO organization Shiraho Conservation Council for Bountiful Seas (SCCBS) was established to foster community-based coral reef conservation. The council spent 2006 reconstructing a stone tidal weir, mainly for the purpose of stopping soil from agricultural lands flowing off and destroying local coral gardens. This also supported local communities settled in these areas to have interest again in healthy and resilient inshore areas.

In addition to members of the NGO organization, local school pupils and their PTA groups participated in the reconstructing activities.

As a proper understanding of the stone tidal weir and its ecological function have expanded among all generations in Ishigaki island and eco-tourists to the island, the council succeeded in holding the 3rd Summit Conference on Stone Tidal Weirs at Shiraho hamlet in 2010.


M. Kamimura, 2017, Shiraho Hamlet and the Summit Conferences on Stone Tidal Weirs in Japan, in M. Tawa, ed., Landscapes Having Stone Tidal Weirs, Nishinomiya: Kwansai Gakuin University Press, pp. 21-33.

Contributed by

iwabuchi_40089's picture

Akifumi Iwabuchi Tokyo University of Marine Science and Technology, International Council on Monuments and Sites (ICOMOS)

Other contributors

University of Guam
University of Warsaw
Chikushi Jogakuen University
Mokpo National University
University of the Philippines
University of Dublin
Nelson Mandela University