Madrid: For decades eucalyptus plantations were celebrated as an economic success story in north west Spain. Fast growing and highly profitable the Australian tree species helped fuel the paper and timber industries while transforming vast areas of Galicia’s landscape. However scientists now warn that this green expansion has come at a significant ecological cost.
New research shows that the rapid spread of eucalyptus plantations is contributing to the decline of native bird populations and weakening the region biodiversity. While the landscape may still appear lush and green experts say the ecological functions of these forests are very different from those of native woodlands.
Eucalyptus trees were introduced to the Iberian Peninsula in the 19th century, but their large scale expansion accelerated from the 1960s onward. Today eucalyptus plantations cover around 44 percent of Galicia’s forested land, making them one of the dominant tree species in the region.
The economic benefits have been substantial. Eucalyptus trees can be harvested within 10 to 15 years, providing a steady source of income for landowners and supporting Spain’s paper industry. Native species such as oak and chestnut require decades to mature making them less attractive from a commercial perspective.
However, scientists emphasize that forests are much more than collections of trees. They are complex ecosystems where plants, insects, birds, fungi and mammals interact and depend on one another. Replacing diverse native forests with a single tree species disrupts these relationships.
A recent study conducted around Galicia Fragas do Eume Natural Park found that bird diversity and abundance declined significantly as eucalyptus coverage increased. Researchers surveyed 240 forest sites and observed that native woodland consistently supported far more bird species than eucalyptus plantations.
Several forest dependent bird species were found to be particularly affected, including long tailed tits, goldcrests, marsh tits, Eurasian treecreepers and common chaffinches. These birds rely on insect rich habitats and diverse vegetation layers that are often absent in eucalyptus plantations.
Scientists explain that eucalyptus forests typically have simpler structures, offering fewer food sources and nesting opportunities. Many birds depend on old trees containing natural cavities for nesting but eucalyptus plantations are usually harvested before such features can develop.
Researchers also found that mature native trees play a crucial role in maintaining healthy bird populations. Mature eucalyptus trees were unable to replace the ecological functions provided by native woodland.
The environmental impacts extend beyond birds. Eucalyptus trees release chemicals that can inhibit the growth of surrounding vegetation a process known as allelopathy. This reduces the diversity of shrubs, herbs, and young native trees beneath the canopy.
Freshwater ecosystems may also be affected. Falling eucalyptus leaves can alter the activity of decomposers in streams and rivers, potentially disrupting aquatic food chains that support insects, fish, amphibians and birds.
Experts warn that biodiversity loss often occurs gradually rather than through sudden collapses. Reduced insect populations, fewer nesting sites and simplified food webs can slowly transform ecosystems over time.
Despite these concerns researchers are not calling for the complete removal of eucalyptus plantations. Instead they recommend creating corridors of native vegetation within plantation landscapes and preserving eucalyptus free areas to provide wildlife habitat while maintaining forestry production.
The findings highlight an important lesson for conservation efforts worldwide. While tree planting can support climate goals and economic development, experts stress that true ecological restoration requires more than simply increasing tree cover.
Spain eucalyptus expansion demonstrates that a landscape can remain green while losing much of the biodiversity that once made it a thriving ecosystem.