Planting more trees is often seen as a simple solution for protecting nature. Across farmland, rows of trees are commonly added to improve biodiversity, prevent wind damage, and create shelter for wildlife. But new research suggests that tree planting does not always help every species equally, as per a report by Science Daily.
A study of agricultural wetlands in Japan has found that shelterbelts, lines of trees planted as windbreaks, can create winners and losers among bird populations. While some birds benefit from these wooded areas, others that depend on open grasslands and wetlands may decline.
The findings, published in the Journal of Environmental Management, show that conservation strategies may need to consider the needs of different species before changing landscapes, as per a report by Science Daily.
Can planting trees harm some bird species?
For years, conservation programs have encouraged farmers to add trees and hedgerows because these features are generally considered good for wildlife.
Known as shelterbelts, these woody landscape features can provide shelter, nesting areas, and habitat for certain species. However, researchers say their impact can depend heavily on the environment where they are introduced.
Much of the previous research supporting shelterbelts has focused on grasslands and croplands in Europe and North America. Less attention has been given to wet agricultural landscapes, such as rice paddies across Asia, which serve as important habitats for many birds.
These wetlands are already declining worldwide, making it important to understand how changes to farmland affect wildlife.
Masumi Hisano, assistant professor at Hiroshima University’s Graduate School of Advanced Science and Engineering and the study’s corresponding author, explained the key question behind the research.
"The central question of our study is, 'Do shelterbelts and other woody linear features benefit all farmland birds equally in agricultural wetland landscapes, or do they create trade-offs by disadvantaging species that depend on open habitats?'"
What happened around Lake Kahokugata?
To investigate the effects of shelterbelts, researchers studied farmland around Lake Kahokugata in central Japan. The area includes wide sections of rice fields, lotus farms, cropland, and pasture. Because the region experiences strong winter winds and storms, shelterbelts are commonly planted to protect agricultural fields.
The location is also important for birds because it sits along the East Asian-Australasian Flyway, a major route used by migratory species.
Birds visit the area during different seasons, with some staying through winter and others arriving during breeding periods. Nearly 300 bird species have been recorded around the lake.
Researchers carried out bird surveys in February and March 2021 and again in June 2023. They used point counts to measure both the number of birds and the variety of species living in different areas.
Which birds benefited from shelterbelts?
The results showed a clear divide. Shelterbelts helped birds that prefer shrubs and habitat edges. These areas created new opportunities for species that are comfortable living near trees.
However, the same tree lines had negative effects on birds that need large, open environments. Grassland birds were especially affected. Researchers found that their abundance was more than 70 percent lower near shelterbelts compared with open areas located about one kilometer away.
Hisano described the effect by saying, "A useful way to think about this is that shelterbelts act like ecological walls."
The researchers explained that even narrow lines of trees can change how animals use a landscape. For birds that depend on open habitats for feeding or nesting, shelterbelts can reduce available space and may also increase exposure to predators.
Why does tree placement matter?
The study does not suggest that trees are harmful overall. Instead, researchers emphasize that where trees are planted can make a major difference.
Adding trees to farmland changes the structure of the environment, and those changes can favor some species while creating difficulties for others.
"Biodiversity-friendly farmland management must balance structural complexity with the ecological needs of open-habitat species, especially in landscapes where wetlands have already been heavily modified by humans," said Hisano.
The researchers say this is especially important because many conservation efforts encourage tree planting without fully considering the effects on entire bird communities.
What could future conservation plans look like?
The research team believes future studies should examine how shelterbelt features — including their width, height, spacing, arrangement, and tree types — influence wildlife.
They also want to better understand indirect effects, such as whether shelterbelts change predator activity or affect how animals move through landscapes.
"Ultimately, our goal is to help design evidence-based agri-environmental policies that work in wet-farmed landscapes worldwide. Rather than promoting a single solution, such as planting more trees everywhere, we aim to support landscape-level planning that combines open habitats and woody features in ways that sustain diverse bird communities and the ecosystem functions they provide. By doing so, agricultural wetlands can remain productive for people while continuing to serve as vital habitats for wildlife in a rapidly changing world," said Hisano.
The study highlights an important lesson in conservation: protecting nature is not always about adding more of one thing. Sometimes, maintaining balance between different habitats is what helps wildlife survive.
FAQs
Do trees always help birds?
No, some species may lose habitat.
What are shelterbelts?
Rows of trees used as windbreaks.
