These two recent papers discuss the diversity and role of ants in coffee plantations, and how the growing method (sun versus shade) impacts these ants. Ants are vital in ecosystems. In tropical forests, there are entire groups of birds (known collectively as “ant birds”) that are completely dependent on swarms of army ants, which they follow in order to prey on insects flushed by the ants. Even more birds are closely or loosely associated with army ant swarms. Coffee growing methods that decrease ant diversity can have a profound impact on other biodiversity in tropical forests.
Armbrecht, I., L. Rivera, and I. Perfecto. 2005. Reduced diversity and complexity in the leaf-litter ant assemblage of Colombian coffee plantations. Conservation Biology 19: 897-907.
This study looked at ants along a gradient of intensification of coffee production, from organic shaded coffee with mixed types of shade cover (“polygeneric”) to unshaded sun coffee. The plantations utilizing organic shaded polygeneric methods had ant populations that most resembled natural forest. As the method of coffee production intensified (went from complex shaded systems to simple sun systems), ant diversity decreased.
Roberts, D.L., R. J. Cooper, and L. J. Petit. 2005. Use of premontane moist forest and shade coffee agrosystems by army ants in western Panama. Conservation Biology 19: 192-199.
Two species of army ants were studied, and found in natural forest and in shade coffee plantations, including those not close to natural forest, but not in sun coffee plantations. In sun coffee plantations, there was less leaf litter for ants to forage and fewer places for the ants to set up “bivouacs” (resting places).