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According to a new study by the EHU's BEZ-EKOFISKO research group, the choice of using eucalyptus in forestry needs to be reconsidered. The research highlights an urgent need to conserve and restore native forests, as the composition of bird species has been found to vary between eucalyptus plantations, pine plantations and native forests.

Pine and eucalyptus plantations established in place of local forests have been expanding in the northern part of the Iberian Peninsula. In the Basque Autonomous Community (BAC), for example, the surface area of eucalyptus plantations doubled between 2005 and 2024 due to the substitution of pine for eucalyptus due to pine diseases.

Today, "nearly 55% of the surface area of the BAC is covered by trees: about half of that area corresponds to natural forests and the other half to plantations (about 25% corresponds to the insignis pine, and just under 7% to eucalyptus)," explained Unai Sertutxa, a researcher in the EHU's department of Plant Biology and Ecology.

Eucalyptus has excellent growth rates and is very profitable in the paper industry, but there is little information about the environmental impacts that eucalyptus plantations may exert on an area.

So members of the EHU's BEZ-EKOFISKO research group are exploring how eucalyptus plantations affect plants, birds and land-based microorganisms. In a recent paper in Forest Ecology and Management, they reported how the diversity of bird species varies when native forests are compared with pine and eucalyptus plantations, and they evaluated the basis for these differences (including vegetation, surrounding landscape, forest structure, location, and deadwood).

The counting and study of bird species was carried out on 20 or so plots of each type of tree system in the BAC, thus estimating the wealth of bird species and their abundance. They also studied the kinds of interactions that take place between birds and plants.

As Sertutxa pointed out, "In this study, we saw that bird species vary according to the type of system and that on eucalyptus plantations there are significantly fewer bird species than in native forests or on pine plantations: The wealth and abundance of the species are lower."

On the other hand, although pine plantations host several species of forest birds, the bird communities are not the same as those of native forests. "This shows that native forests are unique in terms of bird habitats," said Sertutxa.

Natural forests also protect open-area bird species

The results of the study reveal that "local forests are important for preserving bird communities. Local plant species provide living organisms with essential resources for both forest birds and open-area ones (e.g., grasslands, thickets, etc.)," explained Sertutxa.

In fact, the EHU researchers also detected open-area bird species in native forests, which means that "natural forests not only serve to protect forest species (such as the nuthatch, the jay or the short-toed treecreeper), but also serve to protect species that live outside the forest (such as the song thrush and the goldfinch)."

As the results of the study of the interactions between birds and plants show, "Birds use local vegetation more than exotic vegetation; they have very little interaction with exotic vegetation." In fact, the diversity and structure of local forest plant species offer birds a wider choice than more simple plant communities of tree plantations. Furthermore, the researchers noticed that "more than anything else birds have a relationship with plants that produce fruit (and, less, with trees)," he added.

In light of all this, "it is urgent to conserve and restore native forests if we want to maintain bird diversity," said Sertutxa. It is important to use sustainable forest management strategies that prioritize biodiversity conservation in order to have resilient landscapes.

This study shows that "perhaps eucalyptus plantations need to be reconsidered. In Biscay, for example, the ban on eucalyptus cultivation is coming to an end (2025) and the time has come to make decisions. So in view of these results, we believe that it may be better to rule out eucalyptus and explore other paths," said the researcher.