Tokyo: Planting more trees is often seen as a positive step for nature, but a new study from Japan suggests that tree planting projects can sometimes harm certain bird species, especially those that depend on open grasslands and wetlands.
Researchers from Hiroshima University found that shelterbelts rows of trees planted along farmland to protect crops from strong winds create both winners and losers in bird populations. While some birds benefit from the additional trees, others suffer significant declines.
The study, published in the Journal of Environmental Management focused on agricultural wetlands around Lake Kahokugata in central Japan, an area known for its rice paddies and importance as a stopover site for migratory birds.
Scientists surveyed bird populations during different seasons and discovered that grassland bird numbers were more than 70 percent lower near shelterbelts compared to open areas located about one kilometre away. Wetland bird diversity also declined in areas with tree rows.
According to lead researcher Masumi Hisano, shelterbelts act like “ecological walls” that change how birds use the landscape. Species that prefer shrubs and forest edges benefit from the trees, while birds that rely on large open spaces lose suitable habitat.
The findings challenge a common assumption that planting more trees automatically increases biodiversity. Many agricultural conservation programmes encourage tree planting to support wildlife but the study suggests that the ecological impacts depend heavily on local conditions.
Agricultural wetlands play a crucial role not only in food production but also as substitute habitats for many bird species, including migratory birds travelling along major international flyways. Researchers warn that introducing more woody vegetation into these landscapes can unintentionally reduce habitat quality for species adapted to open environments.
Rather than arguing against tree planting the researchers say conservation efforts should focus on balanced landscape planning. They recommend considering factors such as tree placement, width, height, spacing and species composition before implementing large scale planting projects.
The team believes future studies should examine how shelterbelts affect predator activity, habitat connectivity and bird populations across different regions and seasons.
The researchers hope their findings will help policymakers develop evidence based agricultural conservation strategies that protect both biodiversity and food production. They argue that maintaining a mix of open habitats and tree covered areas is likely the best approach for supporting diverse bird communities in a rapidly changing world.
The study highlights an important lesson for conservation planning: more trees do not always mean more wildlife, and successful biodiversity protection requires understanding the needs of different species within each ecosystem.