Until approx. 1970, the relation between organisms and the environment had been examined extensively within a single ecosystem. However, Japan experienced the high economic growth period in the 1960s to 1970s, and interacting ecosystems were uncoupled due to various development actions, such as deforestation, agriculture land development, and the opening of roads.

This led to the local extinction of numerous species, and the consequences tell us that most ecosystems we see are connected with surrounding ecosystems through the material transfer mediated by plants and animals, rather than individual ecosystems being maintained independently.

It has been learned that one ecosystem is nourished by the connection with surrounding ecosystems. Inversely, the destruction of one ecosystem can have repercussions on surrounding ecosystems.
 

Such gathering of various ecosystems is called a landscape. Many organism species use different habitats (ecosystems) in each phase of their life history, and grow and live with the benefit of other ecosystems. It is therefore important to conserve the entire structure and dynamic state of a landscape.
For instance, there is a plant species called Salix arbutifolia. This species grows in an alluvial fan and in an area with an expanded valley floor along rivers that are frequently disturbed by floods, etc. It is important for this species that the water flow migrates frequently. Gravel bars are suitable for Salix arbutifolia to germinate, and such locations are always disturbed by the water from mountain streams. It can grow to the size of a mother tree after an uncommon stable geographic surface has been created accidentally with the abrupt relocation of the water flow. That is, it is plausible to say that the dynamism of a repeatedly migrating river comprehensively provides the necessary growth environment in each growing stage of Salix arbutifolia. In addition to Salix arbutifolia, the many tree species that comprise a riparian forest also require different growth environments between the mother and juvenile tree. Therefore, the growth environments that various tree species require throughout their life cycle can only be maintained by the dynamic movement of the river flow.

The same goes for animals. In spring, when snowmelt water begins to subside, the parent cherry salmon running a river from the sea heads upstream and in early fall lays eggs on a gravel bed in the middle of a riffle and stream pool. The juvenile, hatched in winter, begins to drift downstream on melting snow swelling, and comes to be distributed throughout a river, traveling in a slow-moving portion on the edge of shore. The riparian forest covering the surface of a river reduces the sunlight energy, keeps the water temperature low, and creates an environment in which the cherry salmon, preferring cold water, can make their habitat. Leaves and terrestrial insects also fall from overhanging branches above the water in fall, and the fallen leaves feed benthic animals, and benthic animals and fallen insects feed fishes. In addition, insects emerging from a river and fruits in a forest become valuable food for flying mammals, such as birds, bats, flying squirrels, etc., and a broad riparian forest connected as a corridor is needed for them to travel.
 

On the other hand, forest, river, and wetland ecosystems have changed dramatically at the time of immigration, the postwar period, as well as the high economic growth period. It is imperative to understand the history of such changes in ecosystems. The history of changes in ecosystems is shown in the tree-ring in a forest, and can be learned from pollen and radio isotopes that exist in the sediment in a wetland and at the bottom of a lake. Knowing the state of natural ecosystems prior to land utilization by human beings shows us a leading indicator as to how we should manage ecosystems now and for the future, and provides us with baseline data to conduct nature restoration projects.  
 

Within a forest ecosystem, natural forests were cut down during the extended reforestation after the war, and were replaced by artificial forests, such as the Sakhalin fir and Japanese larch. Those artificial forests are now in the cutting cycle, but Japan’s self-sufficiency in wood is still about 20%. It is possible that wood resources will be depleted along with petroleum oil, as the use of natural resources has increased in emerging countries such as China and India. With respect to natural forests, as well as artificial forests, it is a critical issue to find out how to ensure resources while maintaining the structure and function of an ecosystem. In addition, organism species are drastically decreasing, because river and wetland ecosystems have changed with channelization and sediment- and nutrient-load from the catchment. It is becoming a major social issue to figure out how to rebuild and restore such deteriorated ecosystems.

From the above standpoint, our group conducts a variety of basic and applied research efforts on conserving and utilizing integrated ecosystems in a rational and systematic way from the perspective of a landscape, as well as a forest stand.