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During the mid-20th century, large areas of Israel were transformed by one of the country’s most ambitious reforestation programmes. Millions of pine trees were planted to stabilise soils, combat erosion and create forests on previously open landscapes. At first, the initiative appeared to be an environmental success, with barren hillsides becoming green woodlands. However, decades later, ecologists discovered that the trees themselves were only part of the story. The dense Mediterranean shrubs that naturally regenerated beneath the pine canopy proved to be far more influential in determining which bird species settled in these forests. Their findings revealed that it was not simply the presence of trees, but the structure and diversity of the understorey vegetation, that shaped entire bird communities. The research has transformed how scientists understand forest restoration and biodiversity conservation in Mediterranean ecosystems.
Israel planted millions of pine trees but scientists say the real story was unfolding beneath them
Following the establishment of the State of Israel in 1948, large-scale afforestation became a national priority. Led primarily by the Jewish National Fund (JNF), millions of fast-growing pine trees, particularly Aleppo pine (Pinus halepensis) were planted across degraded hillsides and semi-arid landscapes. The programme aimed to reduce soil erosion, restore vegetation cover, improve water retention and establish new forests in areas that had experienced centuries of grazing, fuelwood collection and land degradation. Pines were favoured because they could establish relatively quickly in the Mediterranean climate and survive on nutrient-poor soils.Over time, however, many of these forests began developing a naturally regenerating understorey of native Mediterranean shrubs, including species such as mastic (Pistacia lentiscus), buckthorn (Rhamnus lycioides) and oak (Quercus calliprinos). These shrubs gradually increased the structural complexity of the forests, creating new habitats for wildlife.
How did Mediterranean shrubs determine which birds moved into the forests
Research by ecologists from Ecological and Forestry Applications Research Centre (CREAF) found in ‘Which bird species respond most to forest structural variation? Implications for biodiversity indicators in Mediterranean forests’ that the composition and density of the shrub layer beneath the pine canopy had a greater influence on bird communities than the pine trees themselves. While the overstorey provided shade and nesting opportunities for some species, the shrubs supplied food, shelter and protection from predators, creating habitats suitable for a much wider variety of birds.Studies showed that forests with a rich and diverse understorey supported significantly higher bird diversity than pine plantations with sparse ground vegetation. Insect-eating birds benefited from the abundance of insects living among native shrubs, while fruit-bearing Mediterranean plants provided food for many resident and migratory species.The researchers found that shrub-rich pine plantations supported many woodland and shrub-associated birds, including some species such as:
| Scientific name | Common name | Why do they benefit from the pine canopy |
| Dendrocopos major | Great Spotted Woodpecker | Feeds on insects in tree trunks and nests in cavities excavated in mature trees. |
| Dryocopus martius | Black Woodpecker | Europe’s largest woodpecker, dependent on large trees for nesting and foraging. |
| Phylloscopus collybita | Common Chiffchaff | Forages among foliage and tree branches, especially during the breeding season. |
| Regulus regulus | Goldcrest | Closely associated with conifer forests, feeding on tiny insects among pine needles. |
| Sitta europaea | Eurasian Nuthatch | Climbs tree trunks searching for insects and nests in tree cavities. |
| Sylvia borin | Garden Warbler | Uses woodland with dense vegetation for breeding and foraging. |
| Turdus philomelos | Song Thrush | Benefits from woodland cover while foraging on the forest floor. |
The research demonstrated that birds respond strongly to habitat structure rather than simply to the number of trees. Even forests with similar pine cover could host very different bird communities depending on how the native shrub layer had developed beneath them.These findings have been supported by long-term ecological studies conducted by researchers in Israel and published in peer-reviewed journals examining Mediterranean forest restoration and biodiversity.
What does this discovery mean for modern forest restoration?
The findings have reshaped conservation thinking well beyond Israel. Modern restoration projects increasingly recognise that planting trees alone does not automatically restore biodiversity. Instead, successful forests depend on allowing native vegetation to regenerate naturally, creating multiple layers of habitat that support insects, mammals, reptiles and birds.Today, ecologists view forest ecosystems as complex communities in which canopy trees, shrubs, grasses and soil organisms all play interconnected roles. In Mediterranean regions especially, maintaining a diverse understorey has become an important objective for improving ecosystem resilience, supporting wildlife and helping forests adapt to climate change.Rather than measuring success simply by the number of trees planted, restoration scientists now place greater emphasis on habitat quality and ecological diversity. Israel’s pine forests provide an enduring example that sometimes the plants growing beneath the trees can have the greatest influence on the wildlife that ultimately calls the forest home. Go to Source
