what they are told is to provide them with an insight into the knowledge, techniques, and way of life and thinking which these experts possess, and from this to learn about the importance of maintaining a connection with nature and other people. It is important for all of us in the modern world to learn from those who carry on traditions that teach us about how to live in harmony with nature and with others.

## (2) The Lessons of Past Natural Disasters

In addition to showing us how to sustainably enjoy the bounty of nature, the ancestral knowledge passed down in each region can also show us how to protect ourselves against its dangers. When we look at the positioning of shrines and temples bordering those areas that were flooded as a result of the tsunami created by the Great East Japan Earthquake, we see that a great many of them are positioned slightly higher than the boundary. The Sanriku region was one of the regions affected by this most recent disaster, but it has also been the victim of major tsunamis.

Photo: Shiiba Villege Tourist Association

several times in the past, such as the Jogan Sanriku Tsunami of 869 and the Keicho Sanriku Tsunami of 1611. It is believed that the reason why many of the shrines and temples escaped flooding during the most recent tsunami is that the ancestors who built them had learned from past experience which areas were most susceptible to flooding and chose sites outside of these areas.

In his work Tensai to Kokubo (Natural Disasters and National Defense), geophysicist Torahiko Terada (1878-1935) stated that old villages are located where they are as a result of natural selection, and with the explosion of urban development taking place in the modern era, we should take heed of this fact. He also pointed out that the damage sustained from natural disasters increases in intensity as civilization advances due to the fact that we overestimate civilization's might while underestimating nature's power. This is an observation that those of us in contemporary society should take to heart.

The Yoshino River has a watershed that spreads across all four prefectures in Shikoku, and it is known for its violent seasonal fluctuations in water level. Annual precipitation for the upstream reservoir reaches 3,000 millimeters, and when it rains, the plains of Shikoku can become flooded in an instant; in times of drought, however, the water can utterly disappear, to the point where the riverbed is visible. The plains of Tokushima are not suitable for rice cultivation, as they are prone to frequent flooding. However, they are suited to growing indigo plants, which thrive in the moist, fertile soil that flooding brings. This fact was not lost on the lords of the old Tokushima domain, and they encouraged indigo production as the signature agricultural product of the region. By 1790, in the middle of the Edo period, indigo cultivation spanned roughly 6,450 hectares. Not only was this the largest area of indigo production in Japan, it was

Figure 3-6-1 Tsunami Inundation Area in the Great East Japan Earthquake and Positions of Shinto Shrines and Buddhist Temples (Otsuchi Bay)

Materials: Created by the Ministry of the Environment, using data from the Geographical Survey Institute

also the highest quality. During this period, the various regions of Japan were proactive about building levees as a means of flood control; however, in the Tokushima domain, the people were anything but proactive about building levees, as they valued the rich soil that flooding deposited, which was indispensable to the production of the indigo that underpinned the domain's finances.

As this example shows, there are cases in which communities do not want to avoid some of the dangers of nature, and want to utilize these dangers as a benefit of nature. It is important to remember that advances in science and technology are not just for repressing the power of nature: with the knowledge passed down from our ancestors, we can even learn to exist in harmony with the dangers of nature.

## (3) Population Decline and Land Use

The above examples detailed how we can learn from our ancestors about how to sustainably use the benefits of nature and confront it dangers; however, the people who could become the future generations to receive this knowledge are disappearing from local communities. It is estimated that by 2050, twenty percent of the regions currently inhabited in Japan will become totally depopulated (Figure 3-6-2). Estimates of population decline are particularly high for hilly and mountainous areas. When the people who manage the natural environment of these regions are gone, it will become even harder to maintain the secondary nature of rural plains and mountains. This could actually mean that passing down knowledge like controlled field burning, which is tailored to a specific region and which shows how to sustainably utilize it, will come to an end.

Furthermore, land usage in Japan today has seen residential areas extend out further and further into regions which are vulnerable to natural disasters, and ensuring the safety of these areas through the construction of levees, landslide barriers, and other kinds of social infrastructure requires a significant cost to be paid. The future population estimates released in January 2012 predicted that Japan's population would decrease significantly nationwide, declining to 86,740,000 by 2060. In light of this, it is important to keep in mind that one option is to ensure that there is no increase in the population size of communities that incur a significant cost to secure the safety of their residents, such as communities prone to frequent natural disasters. Another point is to ensure that Japan's environment is utilized in an efficient way that does not greatly increase the per-capita cost of maintaining the country. In 2007, a report entitled Policies for the Creation of a Safe and Secure Society in Light of the Global Increase in Natural Disasters was compiled and released by the Science Council of Japan. It made the point that, "It will not be easy to avoid a significant population decrease over the next hundred years, and it is therefore essential that regional disaster prevention take depopulation scenarios into account." Also, long-term scenarios incorporating comprehensive decisions, such as how to promote natural succession and actively promote reclamation by natural forests, are needed for areas that will no longer be maintained and managed due to depopulation.

Figure 3-6-2 Rise and Fall in Population in 2050 Compared with 2005

Materials: Created by the Ministry of the Environment based on the values estimated by the Ministry of Land, Infrastructure, Transport and Tourism