Initiative 
Living Things
Dedication 
Sanctuaries Measures Against Wildlife Damage
Protecting Plants From Deer
One of the biggest challenges for our Natural Water Sanctuaries comes from browsing pressure from deer. As shown in these photos, in many forests, all surface vegetation has been eaten by deer, leading to severe soil runoff in some places.
The deer begin by feeding on palatable grasses, but then proceed to eat even poisonous plants. As particular plants are devoured by deer, the corresponding insects, birds and animals that depend on them disappear. For example, when bamboo grass is depleted, Japanese Bush Warblers, Japanese Robins and Siberian Blue Robins vanish as well.
Bird names are listed in accordance with the Check-list of Japanese Birds, 8th Revised Edition.
To protect the plants from deer, we erect fences in select places prone to landslide hazards or where essential plants grow, thereby preserving the resources within for future use as a gene bank.
We also use fences as much as possible during tree planting and periodic forest thinning to avoid providing deer with an excess of food. Without fences, all plant life is at risk from overgrazing, leading to an explosion in the deer population. The ground outside these fences is covered with vegetation that deer tend to avoid, helping to prevent soil erosion and slope collapse.
To fundamentally resolve the issue, it is necessary to control the deer density to an appropriate level. However, since this is difficult for private companies to implement, there is growing expectation for government and municipal initiatives. The Ministry of the Environment has already shifted its policy from deer protection to population management, but full resolution of the issue will take time.
As shown in the photo below, in forests where the deer population density is capably managed, forest-floor* vegetation recovers both inside and outside the fencing.
The ground level of a forest
Experts involved in this Initiative
Tamotsu Hattori
Emeritus Professor, University of Hyogo
Hirao Toshihide
Lecturer, The University of Tokyo
Innovative Deer Fencing
Various unexpected incidents are faced in the process of installing deer fences, such as deer squeezing through ground-level gaps created by rain erosion, or deer using tree stumps outside the fence as stepping platforms to leap over. With each new challenge, we have continued to develop and implement more effective countermeasures. Here are some of our measures.
Raising fence height in areas where deer could jump over
Installing skirt netting to keep deer back from the potential jump zone
Cutting stumps flush with the ground to eliminate jumping platforms
Securing fences with metal stakes in sections where water runs under the fence so that deer cannot slip beneath
The Deer Problem (Japanese Only)
Release Date: March 2014
Learn about our activities related to implementation
Research Conducted with Experts
By combining field investigations with simulations, we ascertain the current health of the forest and forecast its future.
Planning Based on Forest Surveys
Vision Development
In our Natural Water Sanctuaries, conservation and restoration efforts are taken with a long-term perspective spanning 30 to 100 years. The foundation of this effort is the development of a vision.
Since forest conditions vary significantly from one location to another, thorough surveys are conducted to examine both past developments and the current situations. The surveys involve a wide range of tools and information, including topographic maps, aerial photographs, existing vegetation classifications, and the characteristics of individual plant communities*.
Based on the survey results, discussions are held with vegetation consultants, forestry experts, and other specialists to identify issues for each plant community. Subsequently, multiple solutions are proposed for each identified issue, and maintenance policies are determined accordingly. By updating each vision every 5 to 10 years, the Sanctuaries undergo continuous evaluation and improvement.
A community is a group of plants that inhabit the same location.
Experts involved in this Initiative
Regional Environmental Planning, Inc.
Institute of Rural and Urban Ecology Co., Ltd.
MORISHO LLC
AI-Shokubutsu Landscape Planning Office
Implementation of Forest Management Plans
We carry out restoration and maintenance activities in collaboration with professionals from various fields.
Improvement Through Ongoing Surveys
The plants and animals living in forests are constantly changing. In our Natural Water Sanctuaries, ongoing surveys are conducted to inform continuous improvements.
Examples of Our Activities
When working with nature, things don't always go as planned. That's why ongoing surveys after forest maintenance are crucial. Sometimes, results exceed expectations, while other times, efforts end in complete failure. Here are some examples of challenges and discoveries encountered during our activities.
These Deer Weren't Here Last Year
In our Natural Water Sanctuary Okudaisen, 2 to 3 meters of snow accumulates during winter. Because of this, deer had never been seen in the area until recently. However, signs of deer feeding on grass and shrubs started to appear. In response, cameras were immediately set up, revealing a significant presence of deer.
The original maintenance plan for our Natural Water Sanctuary Okudaisen was designed for a forest without deer. Until recently, this sanctuary stood out as an exceptional example where biodiversity thrived and maintenance results were highly effective.
Unfortunately, the unexpected arrival of deer meant the plan had to be completely revised. The first step was to fence off key areas. However, standard metal fences would be damaged as melting snowpacks move during the spring thaw. To address this, we are taking an emergency measure of installing a resin net immediately after the snow begins to melt, and then laying the net flat on the ground when the snow starts to accumulate.
A Mountain Made of Pumice?
When the agreement was signed to create our Natural Water Sanctuary Shizuoka Oyama, the most surprising aspect of the forest management challenge was the fragility of the mountainside. The majority of the existing logging roads had been severely eroded by heavy rains, leaving deep trenches throughout.
In fact, this mountain is composed of alternating layers of volcanic ash from past eruptions of Mount Fuji and small pumice stones called scoria. When roads or other clear-cuts expose the ground, the pumice layer is quickly eroded by water.
As a result, we decided to turn unnecessary logging roads back into forest. Unfortunately, these areas are also frequented by many deer. So, on the flat roadbeds we planted mitsumata (Oriental paperbush) and susuki (Japanese silver grass), which are less palatable to deer. Although susuki is generally disliked by deer, for some reason they like to pull out the young plants. So, we are covering them with agricultural bird netting until they are well-established. The broadleaf trees planted on one side are being protected as individual trees.
New Discoveries During Forest Management
As we continue to repeat our process of R-PDCA (research, plan, do, check, and act), we sometimes make unexpected discoveries. Here are some of the surprising discoveries we have made about wildlife during our forest management activities.
Deer Feeding Almost Exclusively on Fallen Leaves During Winter!
As part of our Natural Water Sanctuary Project Chichibu with the Univ. of Tokyo, we conducted DNA analysis of deer droppings to investigate what they eat in different seasons. The results were astonishing.
During winter, the primary food source for deer turned out to be maples and dogwoods. However, both of these tree types are deciduous. This means in winter, there are no green leaves available to eat. Later, using footage from fixed-point cameras we confirmed that deer herds are feeding on fallen leaves. As you can see, the deer were in good condition and showed no signs of malnutrition.
If deer can survive on fallen leaves, then their food resources are virtually limitless. This discovery invalidates the once-optimistic assumption that if deer eat up all the undergrowth, they will eventually starve and their numbers will decline. We are now developing new strategies to protect forest biodiversity.
Experts involved in this Initiative
Hirao Toshihide
Lecturer, The University of Tokyo
A Possible Solution for Invasive Bamboo?
In our Natural Water Sanctuary Tennozan, a logging road was built alongside a bamboo grove. To protect the road’s embankments (norimen*1), we planted mitsumata (Oriental paperbush) —a species that deer do not eat.
Then, something unexpected happened. Along the sides of the road where mitsumata was densely planted, bamboo shoots stopped sprouting. It appears that mitsumata has an allelopathic effect*2 that inhibits bamboo roots. If this proves correct, it could be a breakthrough solution for controlling invasive bamboo across Japan.
- Norimen refers to the slopes created on both sides of a logging road.
- Allelopathy is the phenomenon where chemicals released by one plant influence the growth of other plants or microorganisms.
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