Beautiful landscapes will not last forever
On hearing the word “mire,” you might imagine magnificent nature. Japan has several famous mires such as Ozegahara, and many people climb or hike to see the majestic scenery and rare flora and fauna when the season comes.
Unfortunately, however, beautiful landscapes will not last forever. The environment changes as time passes. It could change over tens of thousands of years, thousands of years, or even in a relatively short period such as several decades.
I am a geomorphologist, and my research focuses on wetlands, such as mires and lakes, which are located in mountainous areas at an altitude of more than 1,000 meters. I believe that organizing the location of wetlands and their process of formation, as well as clarifying the relationship between past climate change and the time of their formation will allow us to predict the impacts of future climate change on wetlands.
To begin with, the factors that form wetlands are very diverse, but water and a container to store it are basically required, and the balance between water input and output determines whether a wetland is formed. When looking at the actual distribution, you can see a lot of wetlands in areas with heavy snowfall.
So, how do wetlands change their landscape? One reason is change in the amount of water, and the other is change in the landform as a container such that water cannot be stored.
First, the amount of water is related to climate change. Global warming, for example, is expected to exert a large impact on mountain ecosystems. That is because it is not just an increase in temperature, but is related to changes in the water cycle, including mountain glaciers and snow cover.
In the case of Japan, we have two theories: one is that the amount of snowfall decreases (it rains instead) owing to the rise in winter temperatures, and the other is that the amount of snowfall increases owing to the increase in the amount of water vapor in the atmosphere. Regardless, it is expected that the snow-thawing season will come earlier in many mountainous areas in the future.
An earlier snow-thawing season would affect quite a few wetlands. For example, a typical wetlands in the mountain area is called snow patch grassland, where meltwater gradually supplied from accumulated snow brings a humid environment.
In snow patches where snow remains until early summer, the land continues to be wet, but if the snow melts too early, the surface will dry out for a longer period, which can result in disadvantages for maintaining a bog. In addition, the increased amount of evaporation due to the rise in temperature will accelerate the dryness.
Actually, I cannot confirm it at this moment because various other factors such as the amount of rainfall are related. However, our current research is gradually showing that the many mires maintained by a large amount of snow cover are likely to have reduced in area over the past several decades. We will continue our analysis.
On the other hand, wetlands formed in depressions, such as crater lakes where water accumulates in volcanic craters, can also be found in areas with little snow. That might make you think that it will not disappear because it is seldom affected by global warming. However, since mountains are gradually being eroded, they are hardly able to continue as a wetland once drainage channels are formed.
Elucidating wetland mechanisms to predict the future
The disappearance of wetlands affects their ecosystems. First, there is concern about the impact on plants and living things that inhabit wet places. From the viewpoint of protecting rare species, it is desirable to maintain the status quo as much as possible, and losing the beautiful natural landscape would devastate the tourism industry.
So, how can we maintain wetlands in response to such climate change? Actually, this is an extremely difficult issue. Other than human-induced impacts such as land development, it is quite difficult to stop changes in the natural environment over time.
However, I consider that a geomorphological approach to studying the mechanisms of wetland formation and its development process will allow us to predict how wetlands will respond to climate change and identify the wetlands that are relatively easy to preserve.
In the first place, mountain wetlands consist of a complex combination of topography, climate, hydrology, and vegetation conditions. The trigger for formation and the source of water recharge vary as well. For example, the nature of a wetland varies according to whether water accumulates in a crater, forms along a lava flow, or forms in a depression made by a landslide.
Therefore, in the climate change of global warming, even if each location is relatively close to another, some wetlands become dry easily owing to the impact of climate change such as snow patch grassland, whereas some will last for a relatively long time.
I have been conducting research mainly in the Ou Mountains in the Tohoku region, northeastern Japan. For example, superimposing the distribution of snow cover and that of the wetlands in Mt. Hachimantai, which lies astride Akita and Iwate, we can see that many wetlands are also formed in the saddle, where there is little snow. The saddle is a mountain ridge between two or more peaks, where water flowing in from the surrounding slopes, rather than remaining snow, is thought to be an important source of water recharge for wetlands.
In addition, wetlands formed in the depression of landslide areas are recharged by abundant groundwater that springs out owing to cutting off the underground water veins. Therefore, it can be considered that wetlands will be maintained for a very long time without being affected too much by climate change. However, these wetlands may also disappear if erosion progresses, or a landslide reoccurs to bury them.
The existence of wetlands with various formative factors, that is, wetlands with different responses to climate change, in the same region is very important for maintaining a highly diverse ecosystem against climate change.
Complexity of nature in wetland landscapes
I consider that the relationship between past climate change and the time of wetland formation allows us to work out how different types of mountain wetlands will respond to future climate change to some extent. Also, past conditions can be revealed by analyzing wetland sediments closely.
For example, in the heavy-snow regions of Japan, it has been pointed out that the time of formation of snow-related bogs is concentrated around 11,000 to 7,000 years ago, and the wetlands in the Ou Mountains that I have researched is consistent with this.
The period 11,000 years ago is called the Late Glacial Stage at the end of the Last Glacial Age, the coldest period in recent history, and 7,000 years ago was the Holocene climatic optimum (Hypsithermal), the warmest period. In other words, it is thought that the formation of wetlands is related to the fact that it snowed as heavily as the present climate during the transition from cold to warm.
And when looking closely at the sediments in mires, some of them have seen an increase or decrease in the amount of organic matter depending on the depth. Thus, it can be inferred that mires have repeatedly expanded and shrank in response to climate change over several 100 to several 1,000 years. In addition, there are major and minor changes in climate change. Thus, the fact that wetlands have been maintained over a long period of time means they are unlikely to be affected at the level of climate change that occurred during that time.
In addition to the Ou Mountains, our current research is expanding the target area to include Quaternary volcanoes throughout Japan. We are focusing on about 70 volcanoes and checking their aerial photographs and topographic data to find out the location of wetlands.
Our ultimate goal is to analyze the environment of mountain wetland formations using explanatory factors such as topography, temperature, snow cover, and precipitation, to typify mountain wetlands, and to further elucidate the responsiveness of wetland variability (appearance, disappearance, and shrinking) to climate at multiple spatiotemporal scales for each typified type.
Wetlands are formed based on a really complex natural balance. I have always loved mountains and so started researching wetlands related to volcanoes. If you find a wetland while hiking, I hope you will open your map or look at the surrounding landscape and ponder the mystery of how the wetland formed and what the future of the wetland will look like.
As for global warming, I believe it is more important to get in touch with nature directly and feel something from it rather than to simply input what is being reported in the daily news. I would be very happy if my research could inspire people to understand the complexity of nature.
* The information contained herein is current as of November 2023.
* The contents of articles on Meiji.net are based on the personal ideas and opinions of the author and do not indicate the official opinion of Meiji University.
* I work to achieve SDGs related to the educational and research themes that I am currently engaged in.
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