Sapir Polack

Birds, Bushes, Balance

April 15, 2021

A new Israeli study has found a link between the proliferation of shrubs in forests and the variety and quantity of birds in the surrounding area. How will this affect existing shrub thinning policies aimed at preventing severe instances of forest fires?

With spring upon us, the easing of COVID-19 restrictions could not have come at a better time. Israelis can now freely enjoy the season and visit national parks and forests around the country once more. Coincidentally, March 21st was International Forest Day, a day proclaimed by the UN with the aim of raising awareness of the importance of forests around the world and promoting their conservation.  

While trees are perceived as the most prominent elements of forests, other types of vegetation are just as important, like shrubs, for example. In fact, according to a new Israeli study, the conservation of shrubs in forests is vital, as it plays a unique role in protecting the diversity of bird populations in surrounding areas.

Woodlands, vegetation, and shrubs currently cover about a third of the world’s surface, and they make up the natural habitat of about 80% of terrestrial animals including many winged species. The new study, conducted by Dr. Uzi Dagan of the Department of Evolutionary and Environmental Biology at the University of Haifa, found a connection between more complicated sub-forest vegetation and increases in bird habitation.

Sub-forest vegetation includes all vegetation that was not planted in the forest intentionally, but that grew naturally over time, such as shrubs, trees, climbing plants, herbaceous plants, and various annual plants. This vegetation is often perceived as problematic because of the perception that its high-density acts as a “fuel” for large forest fires, thereby complicating firefighters’ task to extinguish them.

Density Invites Variety 

The conservation of shrubs in forests is vital, as it plays a unique role in protecting the diversity of bird populations in surrounding areas. Photo by Kev Kindred.

The findings of the study are based on more than 1,400 birdwatching observations in the pine forests of the Carmel and Ramat Menashe areas. During the study, Dagan examined the extent to which birds were present across a set of designated forest plots, which varied according to the density of sub-forest vegetation in those plots and the birds’ behavior in those different environments.

According to the findings of the study, not only were the number of birds in areas of dense vegetation greater, but the variety of bird species in those areas were also greater. The phenomenon is particularly noticeable within the vicinity of shrubs and trees of certain species, such as European buckthorn (Rhamnus lycioides), a thorny shrub commonly known to occur in Mediterranean forests, which are then referred to as Palestine buckthorn. According to the study, a possible reason for this is that the birds are attracted to fruits that the buckthorn bears, and feeding on them enables the birds to better thrive in an otherwise dry environment.

In terms of their behavior, the birds were found to behave slightly differently in forest plots where the sub-forest vegetation was denser, especially when exposed to external threats. “I checked how the birds behaved when they felt they were in danger due to their proximity to a predator,” Dagan explains. 

“Usually, the birds activate a kind of alarm system to alert other birds that there is a predator nearby, and then they congregate with each other around the predator.” According to Dagan, it can be assumed that the birds are trying to signal to the predator that it is visible and that its chances of catching prey are diminishing. 

“During the experiment, I played recordings of predator noises, and I saw that in denser forests the flocking of the birds was more significant,” he says. According to him, this is evidence of strong social behavior among the birds.

A New Perception of the Forest

According to the findings of the study, not only were the number of birds in areas of dense vegetation greater, but the variety of bird species in those areas were also greater. Photo by Cedric Froehlich on Unsplash.

The study was conducted with the support of the Jewish National Fund, which is also known for actively planting additional forest vegetation. “In the 1950s, the incentive to plant forests was driven by Zionism and economic aspirations. It created jobs for new immigrants and allowed the use of trees for different needs, which was made possible by the lumber industry as was done in Europe,” Dagan explains. 

“In the 2000s, the JNF’s perception underwent a revolution, and its people came to the understanding that the forest is a public resource to be used as a leisure and tourism site. In this respect, birds and birdwatching activities interest many people and thus have tourist value, which encourages its investment.”

There is no doubt that the presence of animals and the possibility of observing a particularly rich population of birds can attract many tourists to nature reserves and forests. But is this an ecologically desirable phenomenon? According to studies from recent years, massive tourism can cause damage to nature reserves and wilderness areas. 

Israel, for example, has a history of forests being damaged as a result of campfires that were not properly extinguished by visitors and hikers. Greater sub-forest vegetation, which includes shrubs and low-hanging branches, can help fire climb up the trees with greater ease, thus creating a more severe fire that is much more difficult to extinguish. This is the main reason the JNF has maintained a complex relationship with sub-forest vegetation over the years, and has proactively acted to thin it, or cut it back. 

As a result, shrubs and herbaceous vegetation are thinned because they increase the flammability of forests, especially coniferous forests (cone and needle-bearing pine forests). Attempts have been made to apply creative and ecological solutions to this issue, such as goat grazing, in which herds of goats feed on the shrubs and branches to thin the vegetation in the areas prone to fires, but it has become less common due to economic-related difficulties. 

“The ecosystem can recover from the fires,” Dagan explains. “Fear of fires cannot motivate decision-making in the field, and there is no need to use seat belts where none are required. Beyond that, it is important to note that, in Israel, forest fires are usually the result of human activities,” he says referring to negligent behaviour and arson. “So, the solution should be more explanatory and include various means of enforcement and supervision.” 

However, Dagan believes more tourism in the area will not disturb the wooded areas or the population of birds that live there. To him, it is still important to encourage people to visit the great outdoors. 

“Ultimately, we want people to enjoy the woods, and to have overgrown forests and corners where you can sit and watch the birds,” he says. Dagan explains that even if a disturbance to the birds occurs, it would be very minor. “This is not what will harm the ecosystem. In the end, the presence of the hikers does not interfere with the birds living in the forests or their nests.”

Greater sub-forest vegetation, which includes shrubs and low-hanging branches, can help fire climb up the trees with greater ease, thus creating a more severe fire that is much more difficult to extinguish. Photo by Matt Howard on Unsplash.

Aiming for Balance

“In light of the rising risk to the forested areas of Israel due to increasing population density and the impacts of climate change, the vegetation in forests must be managed in a balanced manner, which on the one hand will reduce the risk of fires, but on the other hand, must preserve as much biodiversity as possible,” says Dr. Adi Levi, Scientific Director of the Israeli Association for Ecology and Environmental Sciences and Head of the Environment and Sustainability Division at Achva Academic College. 

“Preserving a certain percentage of the vegetated areas in the forest according to the new research recommendations, alongside treating areas that are sensitive to fires or those adjacent to buffer zones, roads and trails in the forest, could create a situation that benefits biodiversity without disrupting forests’ resistance to fires.”

This ZAVIT Article was also published in The Jewish Journal on 14 Apr. 2021


       







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