Research: Meta-analysis of biodiversity loss in coffee farms

Biodiversity loss in Latin American coffee landscapes: review of the evidence on ants, birds, and trees.  2008. Philpott, S. M. et al. Conservation Biology 22:1093-1105. doi:10.1111/j.1523-1739.2008.01029.x

At a recent ornithological conference I attended, I saw a presentation on this paper by one of the authors, my friend Tom Diestch. The authors examined multiple studies of biodiversity impacts of shade coffee management in Latin America (excluding the Caribbean). They wanted to see if there were any patterns to biodiversity loss in these systems. Their results were not surprising. For all taxa (trees, ants, and birds), there was a loss in the number of species as shade management went from rustic to highly-managed shade monoculture or sun coffee.

Compared to forests, there are losses of ant and bird species in most coffee systems, with the exception of rustic shade coffee farms, which had equal or greater ant and bird species richness (number of species) than nearby forests. Most sensitive to habitat changes of the three taxa were ants.

Resident birds, and species specialized in foraging in the canopy or understory, were more impacted by increased management (e.g., less shade) than were migratory species or those that are able to forage in multiple strata. Thus, the diversity of tree species and vegetation characteristics associated with less intense shade management -- higher tree density, more vegetation layers, height of canopy and understory -- were very important to birds.

The authors made several recommendations:

• Since species are lost whenever forest is managed, remaining forest patches should be preserved.
• Rustic coffee should be encouraged -- but not to the point where forest is being cut down or substantially disturbed to grow coffee.
• Sun coffee and similar intensively managed farms should be restored to multi-story canopies with more diverse shade to provide more habitat, and native trees should be included in the restoration.

Many farmers believe that shade coffee results in a lowering of coffee yield. Studies have indicated however that optimum yields come in at around 40-60% shade, and that shade actually helps farmers due to decreased pests (if predators are present) and increased pollination services.

The authors speculate that low production in rustic shade might actually be due to a lack of attention to the crop, and measures can be taken to increase yield without removing vegetation. If there is lowered yield and farmers do take an economic hit, then consumers or other funding mechanisms (e.g., a "payment for ecosystems services" program) should pay a premium to farmers who grow coffee under rustic conditions.

You get what you pay for. I know I'm willing to pay a little more to preserve biodiversity.