The power of the crop: How coffee farms could enhance mammal biodiversity

Doctoral student Amanda Caudill says coffee is one crop that shows great promise in agroforestry. “The way in which coffee is grown and managed can have a huge effect on biodiversity and the types of mammals it attracts,” Caudill says, a student from the University of Rhode Island in the United States. “The main point of difference could be the varying degrees of shade tree species planted within the coffee, which is known as shade coffee or sun coffee.” 
Caudill says the underlying question would be: ‘How do we enhance coffee habitat for mammals?’ “We know that mammals are abundant in rainforests, but we don’t know what type of coffee habitats would be more hospitable for them,” she says. “Mammals are attracted to rainforests because they have all the resources that they need there, but if they’re travelling through coffee plantations with more tree diversity or food available, they would then stay in coffee more, which could be what we’re seeing – but it’s too early in the research to tell.” After months of planning and revising her research study, Caudill travelled to Costa Rica and set up three field sites in Catie, Jicotea and Aquiares, with the assistance of a university grant. Within these coffee farms, Caudill is looking to assess mammal diversity and define which habitat parameters are important to mammals, by doing vegetation analysis to see where there’s a high abundance and diversity of creatures. To evaluate the mammal biodiversity, Caudill set up grids on the three sites in a parameter of 500-square-metre grids. Using direct and indirect sampling techniques to gather her results, she placed 242 small Sherman traps, (a box-style animal trap designed for the live capture of small mammals) on the three farms, two every 50 metres, to bait the creatures. Each morning, along with rotating field assistants, Caudill goes through a routine check of the traps for mammals, which are then weighed, measured and tagged with an identification number. “The majority of the mammals that we capture are small mammals, mice and rats, with a very small fraction of captures or sightings of medium-sized mammals such as possums, coatis and anteaters,” Caudill says. “Most of the mammals don’t eat the coffee berries as a food resource, it’s more the shade trees within the coffee farms that could provide a food resource such as seeds or fruit.” Caudill says the most common mammal species she’s captured is the Dusky Rice Rat (Melanomys caliginosus).  She says one of the most interesting species that she’s seen is the mouse opossum (Marmosa sp.) which is the size of a mouse with a prehensile tail and opposable thumbs on its feet like the larger opossums. So far, Caudill has noticed that the number of mammals captured over the three sites varies, which may lead to some interesting findings as the numbers vary greatly. For instance, at Catie, she captures an average of around 35 mammals during a two-week sampling period; in Jicotea around 95; and in Aquiares usually around 200. Caudill’s field research also extends to coffee plantations in India and Kenya, where she is performing similar studies on a smaller grid parameter. She says the study in Costa Rica is the largest one by far, in terms of duration and area. Once Caudill analyses her results, she wants to go back to the Costa Rican farms and recommend sustainable farming practices to protect biodiversity, and offer suggestions to coffee certifiers as to how best enhance mammal diversity within coffee farms. Caudill says coffee certifications such as Bird Friendly and Rainforest Alliance are a good way to promote and enhance mammal biodiversity because it requires that shade trees be planted within coffee farms, and a reduction in chemicals used in crops. Coffee certification then provides the farmers with a higher premium for their coffee for managing the areas using biodiversity-friendly practices. “The Aquiares farm is Rainforest Alliance certified, so it will be interesting to see if this has anything to do with the overall results,” she says. “You could think organic coffee would have a high diversity and an abundance of mammals. We only have one part of the plantation that is organic [Catie], but we’re not finding very much there at the moment,” she says. Caudill says she’s happy to be doing such a detailed study in the field. “I love being outside, I love being able to hike around, see different trees and mammals in wildlife and the overall goal of trying to create habitats to conserve wildlife. It’s nice to be a part of something that means something,” she says. “There are so many different moving pieces to this study – looking at the socioeconomics of the coffee farmers, the land-use around coffee farms, chemical use, the reasons for them and all the ecosystems. All these things are all intertwined, it’s fascinating. ”