Forest cover and type of environment shape functional diversity of insectivorous birds in the Atlantic Forest

According to a study conducted by researchers in the state of São Paulo, Brazil, more deforested areas have fewer species that are more similar to each other and perform the same ecological functions. The authors say this phenomenon compromises the resilience of the ecosystem.

By Emilio Sant’Anna  |  Agência FAPESP – Five centuries of economic exploitation and deforestation have left deep scars on the Atlantic Forest. A study published in the journal Environmental Conservation points out one of these scars by showing that forest cover and the type of environment are responsible for shaping the functional diversity of insectivorous birds in the biome. The research reveals that forest fragmentation can lead to the loss of species that perform specific ecological functions, such as pest control. It also highlights the importance of maintaining connectivity between forest fragments to preserve biodiversity and essential ecological functions.

Researchers from the Federal University of São Carlos (UFSCar) and São Paulo State University (UNESP) conducted the study in Brazil with support from FAPESP (projects 13/50421-2, 20/01779-5, 21/08534-0, 21/10195-0, and 22/10760-1). The area surveyed was the ecological corridor of the Cantareira-Mantiqueira region in the southeast of the Atlantic Forest in the state of São Paulo. It covers approximately 700,000 hectares and connects the Cantareira State Park with the Serra da Mantiqueira State Park. The region consists of various landscape mosaics with varying degrees of forest loss and different land uses.

Most of the forest remnants are smaller than 100 hectares, isolated, and composed of secondary forests in the early to medium stages of succession. These areas are surrounded by various forms of land use, such as pastures, small-scale agriculture, forestry, and regenerating forests, as well as urban areas.

The results showed that areas with greater forest cover are home to a greater number of species with different ecological functions. Areas with less forest cover have reduced functional diversity, which compromises ecosystem resilience and the provision of essential ecological services.

“This is particularly important in our study areas, which are often made up of secondary forests. In other words, these regions are now home to only a fraction of the species they originally had, due to the degradation the environment has suffered,” says biologist Enzo Coletti Manzoli. He conducted this research during his master’s program at UFSCar under the guidance of Augusto João Piratelli, a professor at the Department of Environmental Sciences.

Sensitive species

The Atlantic Forest covers about 15% of Brazil’s territory and spans 17 states. Over 70% of the Brazilian population lives in these regions, which account for 80% of the country’s gross domestic product (GDP). According to data from the SOS Mata Atlântica Foundation, only around 12% of the forest’s original cover remains today.

In addition to forest cover, the type of environment plays a crucial role. Although secondary forests and regenerated areas are not equivalent to primary forests in terms of biodiversity, they still provide important habitats for insectivorous bird species. However, portions that are highly urbanized or converted to intensive agriculture have shown a drastic reduction in the functional diversity of these birds.

“Deforestation and fragmentation have been the main factors impacting bird species in recent decades. In our research, we realized how these impacted environments can contain fewer niches available for bird species to occupy. Consequently, the behavior of the communities is affected, which can lead to a gap in the compensation dynamics between species,” explains Manzoli.

One of the most concerning findings was that forest fragmentation can result in the loss of species that perform specific ecological functions, such as pest control. This is because species with unique characteristics are often sensitive to habitat loss and environmental changes. “This means that specialist birds and their ecosystem functions may be being excluded from these environments, as there are already generalist species occupying the niches that these birds need to occur in these regenerating forests,” says Manzoli.

The consequences of this loss of functional diversity extend beyond the degraded forest itself. Areas occupied by plantations, which were originally forests, can also be affected by the reduced presence of insectivorous birds. In other words, the economic activity responsible for cutting down the Atlantic Forest suffers from the problems it has caused the biome.

Piratelli points out that pasture areas represent only a small portion of the original avifauna. Meanwhile, environments such as wetlands are home to species that are not found in more forested areas. “Habitat fragmentation and degradation can lead to local extinctions and the loss of ecological functions. This is concerning for both the conservation of Atlantic Forest biodiversity and agricultural production,” says the research supervisor.

The researchers used a combination of field methods, including observations and recordings of bird sounds, to catalog the species present in different study areas. They applied advanced statistical analysis techniques to assess the relationship between forest cover, the type of environment, and the functional diversity of the birds.

The research highlights the need to integrate biodiversity conservation with sustainable land use practices. In areas where agriculture and urbanization are inevitable, measures such as creating protected areas, sustainably managing secondary forests, and implementing biodiversity-friendly agricultural practices can mitigate negative impacts on bird functional diversity.

“The predictive power of functional diversity indices can be very useful in supporting decision-making about land use projects. We can have environments whose diversity is low, but whose birds are functionally very different from each other and therefore provide more varied ecosystem services,” Manzoli explains.

The study’s authors also emphasize the importance of conservation policies that promote the restoration and connectivity of forest fragments, as well as the importance of considering functional diversity when making land use decisions. “The next steps are to verify how ecosystem services are affected and quantify in ecological models how much this is reflected economically,” says Manzoli. “In my PhD, we’ll test the impacts on ecological functions together with the impact on functional diversity indices. I’m looking forward to seeing the new results.”

The article “Forest cover and environment type shape functional diversity of insectivorous birds within the Brazilian Atlantic Forest” can be read at: doi.org/10.1017/S0376892924000080.