By John Barrat
Scientists have long known that in the tropics shade-grown coffee plantations provide critical habitat for migratory and resident birds. Now a new survey conducted in Costa Rica reveals that shade coffee farms also harbor small mammals in greater species diversity and in greater numbers.
During a seven month study researchers used live traps and camera traps to survey a variety of small mammals living in three different habitats in the mountains of Costa Rica: forests, shade coffee plantations and sun coffee plantations.
“We found that both forests and shade coffee plantations had significantly more species of small mammals and in a higher abundance than sun coffee plantations,” says S. Amanda Caudill, an ecologist at the Smithsonian Migratory Bird Center of the Smithsonian Conservation Biology Institute, who led the study. One of the reasons is that shade trees may provide more food—fruit and seeds—for small mammals, Caudill explains.
“Prior diversity research on coffee plantations has been dominated by bird and insect studies,” Caudill adds. “This is one of the few studies to focus on small- to medium-sized mammals in coffee plantations.”
The study was published in a recent edition of the journal Agriculture, Ecosystems and the Environment.
The dusky rice rat, Alfaro’s rice rat, northern raccoon, nine-banded armadillo, Mexican deer mouse, rabbits, mouse opossums, grey 4-eyed opossum and the northern tamandua were all among the 17 different species of small mammals recorded by the researchers during the survey.
Mammals clearly benefit from the increased canopy cover and vegetation complexity that shade coffee provides, Caudill says. In fact, some of the study sites showed no significant difference between forest and shade coffee for small mammals diversity.
On shade coffee plantations coffee shrubs are grown and nurtured beneath a canopy of tree cover. These farms are basically artificial forests devoted to coffee production and require less maintenance, pesticides and fertilizer. On sun coffee plantations the coffee shrubs are planted in the direct sun.
“Coffee is grown in what is called the ‘bean belt’ and it overlaps areas of high biodiversity which makes it a very interesting system to study, especially for biodiversity conservation,” Caudill says.
“The way coffee is managed and the way that it is grown can significantly influence the biodiversity that a farm and its surrounding landscape can support.
“On a broad scale, landscape perspective, when there was a lot of sun coffee in the landscape we saw a decrease in small mammal abundance and richness in the entire landscape.”