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Shade grown coffee has been touted as being bird-friendly, but a new study published in Current Biology says that shade coffee farms also help maintain genetic biodiversity in the rain forests, and can serve as focal points for tropical forest regeneration.
Study authors Shalene Jha and Christopher Dick at University of Michigan originally intended to find out if shade coffee farms help nurture native insects that pollinate coffee plants. Jha’s original fieldwork focused on one particular plant which is pollinated in an unusual way called “buzz pollination”.
The plants are pollinated when bees grab hold of the flowers and vibrate their flight muscles, shaking the pollen loose. Only native bees perform this maneuver, so Jha htought that the health of the miconia plant would be a good indicator of how well the native pollinators are pollinating native and local plants.
But, said Jha, the more she studied the plants the more she realized that there was a deeper story to be told. She enlisted the aid of Dick, an assistant professor of ecology and evolutionary biology, and the pair studied DNA samples that Jha collected from Miconia trees growing in the coffee farms and forest fragments in her target area.
The three farms that Jha studied were typical of many other coffee farms in Mexico. They had been clear-cut and burned in the late 1930s, then planted with coffee bushes and canopy trees. The native trees like Miconia have been allowed to grow into the understory because they prevent soil erosion.
Jha and Dick used genetic analysis to figure out if trees were all “siblings” that sprouted from the same mother tree or whether they were a “genetically diverse assortment” grown from different mothers.
Surprisingly, the research showed that trees in the forest were very related to each other, suggesting that the seeds in the forest don’t move very far from their mothers. In the coffee farms, however, the DNA analysis told a very different story. There, even trees that grew in close clusters were grown from seeds of different mothers. The researchers speculated that it’s because the seeds on coffee farms are spread by large birds that move throughout the coffee farms rather than staying within a small cluster of trees.
In other words, by being friendly to birds, shade coffee farms support the spread of different genetic strains of trees, connecting patches of the surrounding forests. In addition, Jha postulates, shade coffee farms may serve as reservoirs for future forest regeneration, since the farms generally stop producing in less than a century. At that point, the genetic diversity and native wildlife will make it easy for the rain forest to regenerate itself.
Jha says that despite the current popularity of shade grown coffee, many farmers are converting their traditional shade farms to sun-intensive industrialized plantations and cutting down the overstory to make it easy for machines to get at the coffee trees. Says Jha, “It’s more important than ever to pay attention to biodiversity.”