Focusing on coral reef island systems located in the Ryukyu Arc as well as in the tropical and subtropical western Pacific, we are elucidating the connections between land and sea through the water cycle, the biocultural diversity and community capability, and the evolution and structure of organizations and institutions that govern the use and management of multiple resources. By integrating and visualizing the above interconnected components, we aim to shed light on adaptive governance of multiple resources based on the water cycle.

People living in tropical and subtropical islands where coral reefs develop utilize the blessings of limited water resources such as groundwater and spring water, as well as marine and forest resources.

Water circulates between the land and the sea while changing its shape, connecting the coral reef ecosystem and the land, and nurturing the biodiversity and culture unique to the region.

However, recent land use and socioeconomic changes have led to the depletion of water resources and deterioration of water quality, as well as changes in precipitation patterns due to climate change, rising sea temperatures and sea levels due to global warming, and ocean acidification. Due to changes in the marine environment, the deterioration of coral reef ecosystems is progressing, making it difficult for people to use natural resources such as water resources, fisheries resources, and forest resources, that is, multiple resources.

Therefore, we are conducting research to strengthen “adaptive governance,” in which social mechanisms and institutions for environmental conservation and natural resource management are adjusted to the situation together with local people, so that people living on coral reef islands can continue to use multiple resources.

To this end, in this project, we will first clarify the actual state of the water cycle and multiple resources by analyzing groundwater and coral reef ecosystems, and understand and predict the responses of multiple resources to socio-economic changes and climate change. In addition, using a historical ecological approach, we will elucidate the connections and diversity between organisms and cultures in the lives of island people, and elucidate the mechanisms that sustain the foundations of survival in island communities.

On the other hand, through behavioral science and institutional analysis, we will clarify the transition and multilayered nature of the system, organization, and awareness of adaptive governance. In addition, we will act as a bridge to create new value by visualizing and integrating the relationships between scientific knowledge, indigenous knowledge, policy knowledge, and other knowledge necessary for adaptive governance.

Through these results, we hope to shed light on the connections between land and sea through water cycle as well as on the adaptive governance of multiple resources, in order to contribute to the realization of a resilient nature-symbiotic society in coral reef island systems.

What we know so far

In the southern part of Okinawa Island, nitrate nitrogen contamination in groundwater has become a problem in some areas. We have developed an accurate evaluation method for nitrogen sources (chemical fertilizers, livestock manures, etc.) using several stable isotopes to lead to effective pollution control measures.

In the Sekisei Lagoon, located between Ishigaki Island and Iriomote Island, a field survey revealed that the coral density becomes almost zero when the concentration (threshold) of phosphate (accumulated phosphorus) adsorbed in the calcareous sediment exceeds a certain level. By setting this threshold as a target, it becomes possible to determine and implement an acceptable land-derived load, and it is expected that coral coverage will recover in the future.

From the perspective of behavioral science, we conducted an awareness survey on the compatibility of human movement and infection control during the corona crisis on an island with limited resources. It has become clear that negative reactions to the movement of people are mitigated by the acquisition of health certificates and the effects of infection control certification by local governments.

Noteworthy items

We built a 3D water circulation simulation model for the southern part of Okinawa Island. We created a projection mapping model (P+MM) that can visualize various types of information, such as groundwater flow and changes in land use, and used it in the Yaese town hall and regional roundtable meetings (Photo 1).

In addition, children also participated in coral-coring survey at Yoron Island (Photo 2). By analyzing coral growth rings from ~200 years ago to the present, we will elucidate how the coral reef system of Yoron has changed due to human activities.