Stream friendly coffee: evaluating the impact of coffee farming on high-elevation streams of the Tarrazú coffee region of Costa Rica

Abstract

Coffee farming is an important practice in the tropics, but studies addressing its effect on streams, especially at high elevations in high productivity regions, are limited. We evaluated streams draining the high-elevation coffee farming region of Tarrazu, Costa Rica, in terms of water quality and benthic macroinvertebrates over the course of a year. We compared our observations to regulatory benchmarks to determine overall condition, and compared our sites in terms of riparian vegetation (i.e., canopy cover, and riparian width) to determine the role of this management practice. Overall, we found that most streams fell within recommended water quality criteria and supported high proportion of pollution-sensitive taxa. Nevertheless, we found high levels of conductivity during the drier period of the year, which may signal agrochemical pollution. Also during the drier period, we found significantly higher diversity, % scrapers, and % predators, which suggests a boost in basal food sources associated to the observed high conductivity levels. We found that riparian buffer widths were not associated to improvements in water quality indicators or bio-integrity parameters on our sites. However, canopy cover was positively correlated to % shredders and family diversity, and negatively correlated to certain tolerant taxa. Our findings help to better characterize a system that is of great economic importance in the tropics, but that remains relatively under studied. It also helps inform management practices to enhance the potential of coffee agroforestry systems in promoting tropical biodiversity conservation within aquatic ecosystems.