Over the past 10 years many areas of once-forested land degraded by cattle in the Amazon have been converted to oil palm. To measure how the oil palm plantations may affect biodiversity, researchers studied orchid bees in oil palm plantations and patches of secondary forest along rivers in Brazil.
To the researchers’ surprise, they found that these patches held just as many species of orchid bees as large tracts of primary forest in protected reserves. Their findings, published in Apidologie in late 2017, offer evidence that small tracts of forest embedded in oil palm plantations may help plants and animals survive deforestation.
The Belém Endemism Center is a vast area, 199,211 square kilometers (76,900 square miles) of rainforest that stretches from northeastern Pará to northern Maranhão. Scientists consider it one of the most biodiverse regions of the Amazon, and also one of its most endangered.
“We were eager to study orchid bees in this region with the recent expansion of oil palm plantations,” said Thaline Brito, a pollination biologist at the Federal University of Pará in Belém, Brazil, and a lead author of the study.
Orchid bees are known for their striking colors and “perfume-making” behaviors. Male orchid bees gather odors from different flower species to create a unique perfume, which they store in their hind legs to later attract female orchid bees. There are 250 species of orchid bees, which pollinate 600 species of tropical plants, including economically important plants such as vanilla and Brazil nuts.
Because orchid bees search for different plant species scattered across long distances on the rainforest floor, they are sensitive to deforestation. Because of this, scientists use their presence – or lack thereof – as a proxy for forest health.
Brito and her team set up traps scented with vanilla, clove and other attractive floral odors inside oil palm plantations, neighboring river forest patches, and in distant reserves of intact primary forest.
Researchers expected to find moderate numbers of orchid bee species in the river forest patches, few in the oil palm plantations as orchid bees do not visit oil palm flowers, and the highest number of species in forest reserves.
Instead, they discovered that orchid bee diversity in patchy river forest was similar to that in forest reserves. As the researchers expected, few orchid bees were found in oil palm plantations.
The study’s findings are timely because Brazil’s 1965 forest code, which requires private landowners to keep 60 to 80 percent of their land forested, was recently revised. While the new revisions attempt to curb illegal deforestation by encouraging landowners to register their property boundaries and forest reserves in a national database, the river forest patch requirement is significantly reduced, in some cases eliminated, allowing for more intensive land use. This study is one of a handful of recent studies that show how river forest patches support the survival of plants and animals in deforested areas. Since the forest code revisions in 2012, research indicates the downward trend of deforestation in Brazil has reversed and deforestation has increased 29 percent.
The new study is the first to look at oil palm plantations in Amazon rainforest and their impacts by using rigorous baiting methods to measure orchid bee diversity.
“They are simply the most efficient way to study bee abundance and dynamics,” said David Roubik, senior scientist at the Smithsonian Tropical Research Institute, who has identified over 250,000 orchid bees. He was not involved in the study.
One caveat to the study is that primary forest in reserves may not be completely intact. But the authors say that compared to oil palm plantations and secondary forest, it provides far superior habitat.
“Overall, the reserves are more intact than not, but should not be considered untouched,” said Colin Phifer, an ecologist and coauthor of the study at Michigan Technological University. “Still, I have personally seen three species of primates, including one endangered species.”
Brito, T.F., Phifer, C.C., Knowlton, J.L. et al. (2017). Forest reserves and riparian corridors help maintain orchid bee (Hymenoptera: Euglossini) communities in oil palm plantations in Brazil. Apidologie 48: 575-587. https://doi.org/10.1007/s13592-017-0500-z
Banner image: Study coauthor Colin Phifer holds a recently captured metallic orchid bee. Photo by Colin Phifere