Fossils typically found in limestone in the Ryukyu Archipelago. Top left: corals, top right: rhodoliths (algal balls), lower left: large foraminifers (red arrows), lower right: a large living foraminifer. 

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... rubropunctata, a herb in the mint family, is endemic to the Ryukyu Archipelago (Fig. 7). This beautiful species is not especially rare. Indeed, it is common in a variety of locations, including the northern part of Okinawa-jima Island. Although the species also grows in the southern part of Okinawa-jima Island, its numbers have declined over the past decade. Some populations have entirely disappeared because of en- vironmental degradation caused by human ...

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... crystal growth is an inorganic process, such a speleothem resembles a strange organism. In fact, some coral skeletons in the sea (Fig. 7, circle) appear to be similar in ...

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... large amounts of organic matter transported seaward by the flow of rivers accumulate on tidal flats or in the mangrove forests, the microbes get to work, releasing a pervasive stench of hydrogen sulfide, which is an indicator of dead zone formation. However, when benthic animals are abundant, they will reduce the content of organic matter through their feeding behavior. Several groups of benthic animals, such as depos- it feeders (which eat fine sediments deposited on the tidal flat surface; Fig. 6 left) and suspension feeders (which filter suspended matter and plankton from water column; Fig. 6 right, Fig. 7), co-occur on tidal flats, where they collectively regulate the physicochemical environment. The feeding behavior of the benthos ensures the health of the tidal ...

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... the northern part of Okinawa-jima Island ('Yanbaru'), understory thinning has been performed from the 1970s to the present. Scientific validity of such a management method based on empiricism can be as- sessed based on simulation analyses, as mentioned above. Figure 6 demonstrates an assessment of whether forest growth managed by understory thinning was enhanced. We can see there are few differences in the recovery of forest biomass between managed and intact forests. More importantly, Figure 7 indicates that the number of tree species (surrogating as biodiversity) is significantly reduced by understory ...

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... issued by The Japan Ministry of the Environment lists the Asahina's skipper* and the dark grass blue (Zizeeria karsandra) as "vulnerable"; and the great Nawab (Polyura eudamippus weismanni) (Fig. 7), the orange oakleaf (Kallima inachus eucerca), the bamboo tree brown (Lethe Europa pavida), the Masaki's three-ring*, the Ryukyu three-ring*, the Yaeyama four-ring*, the green flash (Artipe eryx okinawana), and the forest quaker (Pithecops corvus ryukyuensis) (Fig. 8) as "near ...

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... type of stalactite formation, called a "helictite", grows in yet another direction. It has branches in the longitudinal and horizontal directions, as if it had grown in the absence of gravity (Fig. 6). In addition, there is a unique stalagmite formation, the surface of which is covered with numerous small balls (Fig. ...

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... observe the rocks and cliffs along the coasts. Although the surfaces of the rocks are dissolved and have many holes and depressions, you may be able to find fossils of coral (Fig. 7). You may also find white balls. These are also fossils called rhodoliths (algal balls), which consist of many concentric layers. The con- centric layers form as a gravel-sized core is covered many times by calcareous algae and encrusting organ- isms. You may also see large flat fossils that look like "potato chips." These are a type of Foraminifera, as is the star sand. The largest of these attain diameters of 5 cm, making it one of the largest unicellular organisms in the world. The rhodoliths and large foraminifers live in water up to 100 m deep around coral reefs. The presence of these fossils means that the rocks and cliffs were formed from skeletons and shells of calcareous organisms that once lived in coral reefs in shallow water. These rocks formed of calcareous fossils are called limestone. Limestone is found in most of the islands of the Ryukyu Archipelago (Fig. 8). In particular, most parts of Miyako-jima Island are covered with limestone (see section 3-1). ...

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... annual rainfall distribution in the Okinawa Islands. The amount of rainfall in Yanbaru, the northern part of Okinawa-jima Island, is about 1000 mm greater than that in the southern part of the island. Such contrast of rainfall according to topography is usually obvious on a tropical island. According to a scientific report of the University of Guam, rainfall on Pohnpei Island in Micronesia is distributed with huge variation of up to 4000 mm observed. On Okinawa, the water supply system is built to use rainwater from Yanbaru (Fig. 7, right panel). Many dams are located in the northern part of the island, and major aqueducts and water tunnels transport the water to purification plants in the southern part of the island, where the human population is concentrated. It is certain that rainfall induced by sea-breeze circulation in summer contributes to continued water supply, which benefits the population of the ...

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... occurrence of rainfall due to sea-breeze circulation implies that this circulation acts as a water pump, lifting water evaporating from the sea surface to an island. The left panel of Fig. 7 shows the topography ...