What are you aiming to achieve?

We understand that forest and river ecosystems that were previously considered separately, are in fact linked in multiple ways. I would like to clarify those connections. If a forest surrounding the river, for example, covers the surface of a mountain stream, it shuts out the sunlight, and the surface of the stream will be dark, with only dappled sunlight reaching it (Fig. 1). The crown of the forest shuts out sunlight, with the result that the temperature of the water in upstream areas remains low, maintaining an environment in which salmonidae fish such as oncorhynchus masou can live. If light is unable to reach the surface of the water, photosynthesis by aqueous plants such as periphyton is reduced, and in order to survive, organisms within the river must rely on the organic matter produced outside of the stream for most of their energy. Most of this organic matter is in the form of fallen leaves supplied by the forest in autumn. The branches stretching over the water not only supply leaves, but also terrestrial insects, which fall into the stream. Dead trees also fall into the river, and driftwood also plays an important role in the formation of the living environment for fish. In general, when the quantity of driftwood increases, the number and variety of fish in a river also increase (Fig. 2).

Fig. 1 Connections between the river and the forest Fig. 2 Experimenting with the insertion of large wood

 

Most matter flows from the mountains to the sea under the control of gravity. The intervention of living creatures, however, creates a flow from the sea and rivers towards the mountains. In Shiretoko, Hokkaido, the role of the salmonidae, which carry nutrition obtained in the sea upstream, is particularly noteworthy as a mechanism for ecosystem maintenance. Salmonidae swim upstream in order to spawn, and are eaten by bears, raccoons, foxes, eagles and other terrestrial animals; once they have spawned their carcasses are also broken down by other living creatures. Aquatic insects, which are hatched in the rivers, are important sources of food for birds. In this way, all matter from mountain to ocean, and the creatures that live there, are part of this system of recycling.

 

What sort of equipment are you using to do what type of research?

In principle, we use boots, binoculars and a field notebook. When I started at university, I used to wish I could wear a white coat and use a microscope, but I think that boots suit me better. The most important thing in field science is an instinct for nature. The importance of instinct is true in any research field, but nature is difficult to manipulate, so your five senses are necessary in order to glean something general out of a complex mix of phenomena. In order to stimulate the instinct that comes from the five senses, furthermore, it is important to look at a variety of phenomena that actually take place outdoors. When you begin to research connections between ecosystems, you are working with large-scale space. For this reason, it is not always possible to do everything you need to outdoors in a pair of boots, and at times like this we use satellite images and other remote sensing techniques. In order to perform spatial analysis of the images, we also use geographic information systems (GIS).

 

What are you aiming to do next?

Ecosystems are complex networks, typified by food chains, for example, and I would like to be able to explain even one new connection. I am also very motivated by the idea of recreating connections between ecosystems that have been lost as a result of human development. In the Kushiro Wetlands, we are implementing a project attempting to return a river that was straightened back to its original meandering shape (Fig. 3). If we can do this, we will recreate the connection between the river and the wetlands. Furthermore, in the Shiretoko World Natural Heritage Site area, we are improving dams to allow salmonidae to swim upstream, and aiming to recreate the connections between forests, rivers and the ocean (Fig. 4). I believe that this proactive involvement in nature-restoration projects is an important part of my work as a researcher.

Fig. 3 Restoring a meandering river in Kushiro Fig. 4 Improving dams in Shiretoko (above: prior to implementation, below: after implementation)

 

References

(1) Nakamura, F., Koike, Takayoshi (eds.) Forest Science ? An Introduction to Forest Ecosystem Science, Asakura Shoten (2005)
(2) Nakamura, F. et al. (supervisors), Thinking about the Environmental Purpose of Rivers ? Health Checks for Rivers, Gihodo Shuppan (2008)

Fig. 4 Improving dams in Shiretoko

(above: prior to implementation, below: after implementation)