The Japanese larch is a conifer tree native to central Japan and often used in forestry in the northern part of Japan, especially in Hokkaido. It is popular for construction, making pulp and for Japanese bonsai. The human-made forests in Shiretoko lack an underlying layer of other diverse plant life, notably dwarf bamboo, which seemed to deter the bears. Credit: 2024 Tomita and Hiura
Brown bears foraging for food in the Shiretoko Peninsula of Hokkaido, Japan, have been disrupting tree growth in artificial conifer forests, according to a new study published in Ecology. Researchers compared soil and tree samples from human-forested plots with samples from natural forests. They found that the bears' digging for cicada nymphs damaged tree roots and altered the nitrogen content of the soil, which in turn limited the diameter growth of trees.
The phenomenon of bears digging for cicadas, an unusual food source, appears to be restricted to human-planted conifer forests; diversely vegetated natural forests were unaffected. Bears in Hokkaido sometimes suffer from sparse food supplies, but it is not known if this is the reason for their cicada search. These results are important for animal conservation and efforts to return used land to a wild state, highlighting the value of recreating diverse local ecosystems that can support natural wildlife behavior.
On the northeastern tip of Hokkaido, Japan's northernmost main island, sits the Shiretoko Peninsula, and within it the Shiretoko National Park. Designated a World Nature Heritage site, thanks to its thriving ecosystem and diverse wildlife, the peninsula is home to Japan's largest land animal, the brown bear.
It is estimated that almost 500 bears live within the 70-kilometer-long and 25-km-wide strip, making it one of the highest densities of brown-bear populations in the world. Bear numbers in Hokkaido have been gradually recovering since the 1990s, when conservation efforts began in earnest after decades of unchecked culling.
Rather than being an isolated wilderness, thousands of people live and work in the Shiretoko Peninsula, and it is also a popular tourist destination. Since the 1970s, residents and local government have been planting conifers, such as larch and spruce, on abandoned farmland as a way to help return the area to its original forested state.