(CN) — Something strange is happening in the pristine forests of the Amazon.
Biodiversity is declining, even in areas of the world’s largest rainforest protected from human development.
For the past 50 years, conservationists have focused on limiting deforestation in the Amazon to protect its 16,000 species, including one in five of all bird species in the world. Conventional wisdom suggested that preserving forests preserved the species that rely on them for food and shelter. The more pristine the forest, the better it was assumed to support biodiversity.
But a study published Monday by researchers at Louisiana State University found that birds that forage on the forest floor are disappearing.
"What we think is happening is an erosion of biodiversity, a loss of some of the richness in a place where we would hope biodiversity can be maintained," stated LSU School of Renewable Natural Resources professor Philip Stouffer, lead author of the study published in Ecology Letters.
In recent decades, global warming has produced historical droughts in the Amazon, which withered crops and increased forest fires. These disasters led to changes within otherwise untouched forest areas, increasing woody debris on the forest floor, according to the study.
Since 1991, Stouffer has conducted field research in the Amazon. His years of experience in the tropical forests of South America led him to notice that around 2008 it became more difficult to find certain bird species that were plentiful when he began his research.
To test his theory, Stouffer began gathering new data comparable to samples from the 1980s, allowing him and other researchers to analyze changes in species spanning 35 years. Their analysis was aided by the computational modeling expertise of study co-author Stephen Midway of the LSU Department of Oceanography & Coastal Sciences.
Over a period of eight years, Stouffer and his students surveyed 21 forest sites that spanned approximately the same area as the historical data from the 1980s. Researchers utilized a line of nets that were opened at 6 a.m. and closed at 2 p.m. during the traditional dry season, from June to November, to capture the birds, which were identified, processed and released on site. Certain species, including raptors and kingfishers, were excluded from their data to eliminate canopy species that almost never descend to ground level.
Of the 79 species comparable to historical data, 11% were less common in modern forests, while an additional 10% were more common. This led Stouffer to identify two trends: abundance of many species has declined; and bird abundance is more divergent now than four decades ago.
The findings proved Stouffer’s theory, signaling a shifting baseline previously undetected.
“Certain birds are much less common than they used to be,” Stouffer said. “If animal patterns are changing in the absence of landscape change, it signals a sobering warning that simply preserving forests will not maintain rainforest biodiversity.”
Patterns within the declines also emerged. Birds that forage for insects near or on the forest floor declined the most, including the wind-banded antbird, which searches under leaves and other debris to find its prey. Also declining was the musician wren, a shy bird with one of the most iconic voices in the Amazon.
In contrast, the white-plumed antbird, which eats a variety of insects churned up by ant swarms, remains plentiful, leading researchers to theorize that its foraging strategy makes it more resilient.
Birds that eat fruit have also increased their numbers, suggesting omnivorous birds with flexible diets are better equipped to evolve with climate change. “The idea that things are changing, even in the most pristine parts of our planet yet we don’t even know it, illustrates the need for us to pay more attention,” Stouffer said
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