For reasons that will become clearer in a few months, I've become somewhat interested in bio-diversity preservation and eco-system services. Examples of ecosystem services are pollination by bumblebees, decomposition of wastes, and flood mitigation and carbon sequestration by forests.
One of the main problems with ecosystem services is that it is hard to attach to them a monetary value. As a result, decisions to cut down forests, develop lands and interfere with water flows often undervalue these services. Even if there is a value attached to the service, the fact that it is provided by nature makes it harder to tell who should pay to preserve it.
I was recently shown a nice example of where the value of an ecosystem service has been quantified, an no less, in the area of coffee production! In , Ricketts et. al show the value of having a forest close to a coffee plantation. They conduct this study in a coffee farm in Costa Rica, and show that within a distance of 1km from the forest, the benefits of forest-based pollinators (i.e., diversity of bees) can increase the production of the farm by 20%. This observation, as they show, can be directly translated to a monetary value. The basic reason that the proximity of the forest is important is that the diversity of bees in the forest enable better cross pollination among plants (whereas, for example, honey bees typically focus on single branches when flowers are dense). Interestingly, the diversity of bees also reduced the number of peaberries produced, which may be slightly more controversial if your goal is to make money off peaberries (which some do).
Thanks to Gretchen Daily for sharing her article with me.
 Taylor H. Ricketts, Gretchen C. Daily, Paul R. Ehrlich, and Charles D. Michener. Economic value of tropical forest to coffee production. Proceedings of the National Academy of Sciences, August 24, 2004, Volume 101(34). Pages 12579-12582.