Traditional small-scale farmers in southeast Mexico utilise tree canopies to protect their crop and protect against soil erosion. Miconia sp. have been grown in these farms since they were clear-cut and burned in the 1930s. Shade-grown coffee has been known to facilitate colonies of animals through this farming method, but the article in Current Biology details research findings concerning the genetic diversity of the trees themselves. Compared to the same trees in neighbouring forests, the trees forming the canopies for shade-grown coffee demonstrate greater genetic diversity, suggesting the importance of the traditional farming practices in protecting biodiversity.
The research was conducted by Shalene Jha and Christopher Dick of the University of Michigan, United States. Samples were collected from Miconia affinis trees growing in various coffee farms and in forests. The research suggests that seed dispersal may be the reason for greater diversity. While in forests seed dispersal may be limited to forest-dwelling birds, in farms there is potential for dispersal by wider-ranging birds in that a greater diversity of animals may be found there.
The research is important during a time when there is greater pressure to expand farms and eradicate the shade-grown coffee practice in favour of mechanised, sun-intensive farming, where canopies are cut down to facilitate access for machinery. While shade-grown coffee farms actually connect otherwise isolated forest fragments, sun-intensive farming would cut off such potential gene flow and lead to potential loss of diversity through in-breeding within those isolated fragments.
Jha explains, "If seeds are not dispersed, they will remain clumped together under the mother tree, and this will make them easy targets for predators." As a result, seed dispersal is compromised and "gene flow will be limited, and this can result in future plant inbreeding."