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  • Measuring Economic Value of Coffee in a Forest Ecosystem

    If you were assigned the task of making an estimate of the economic contribution that the forest ecosystem services to a coffee plantation, how would you do it?

    Ecosystem services are usually defined as those systems and processes in nature that serve to support and fulfill human life. One important ecosystem service is crop pollination, and this brings tremendous economic value to society. Among the world’s thousands of crop species, only about a third do not need the services of animal pollinators. We know how important bird, butterflies, bees and other animal species are to the propagation of many familiar crops in our farms and plantations.

    The Value of Pollinating Bees to Coffee Yields

    Coffee benefits a lot from the visitations of bees to the coffee tree. Bees that visit a coffee area can increase its yields by as much as 50% compared to areas where bees are excluded. When native habitats, such as forest ecosystems are located far from the plantation, there is less pollinator diversity and visitation rate. The effect of distance from a forest ecosystem is thus a key variable to measure in your economic valuation assignment.

    Economic Valuation of Forest Ecosystem in Costa Rica

    A coffee research study in Costa Rica did exactly that. Given a farm location and a nearby forest patch, the researchers selected 12 sites following a line of gradients from the patches to the farm. There were three distance categories relative to the forest: near (within 100 m); intermediate (700-800 m); and far (1,400-1,600 m). All the study sites contained plants of the same variety (the higher quality C. arabica) and age (8-10 years). There were no managed bee populations in the area, but there were wild honey bees.

    The researchers then chose five healthy plants in each of the 12 sites. On each plant, they selected four branches, matched for length, shade, and vertical position. The chosen branches were randomly divided into two treatments – one, by hand pollination; the other set was not manipulated. When coffee berries had formed and ripened, they then compared the two treatments in terms of three result areas: seed mass, fruit set, and peaberry frequency (peaberries are small, not fully formed seeds).

    Seed mass was measured by harvesting ripe fruits and getting the wet weight of each seed. Fruit set for each branch, or the success rate of pollination, was measured by dividing the number of harvested fruits by the original number of flowers. Peaberry frequency for each branch was measure by dividing the number of peaberries into the total number of harvested fruit.

    The results were then subjected to statistical analyses. Interplant variation (that may be caused by soil chemistry, moisture, microclimate, pruning history, and other cultivation factors) was statistically made uniform (by calculating variation around the mean) to fully isolate the differences in treatment results. Other statistical tools were used to analyze correlations.

    Abundant Pollinators Increases Coffee Yield

    After all the analyses, the researchers found that the abundant and diverse pollinator community supplied by the native tropical forest increased both the quantity and quality of harvested coffee nearby: the fruits were larger and more robust. Native bee species, apparently, are more effective at cross-pollinating plants than honey bees. Native (or wild) bees move among plants more frequently, while managed honey bees focus more on single branches where flowers are dense. Native bees can also deposit more pollen than honey bees.

    The Economic Value of the Forest Ecosystem

    From these results, it was easy to calculate the trade value of the incremental production of the bee-pollinated area. The researchers assumed that pollination effects from forest extend to 1 km, just beyond the bounds of the intermediate sites. The calculations resulted in an incremental income of US$62,000 for the study area (480 ha) or about $129 per hectare (ha) per year.

    By comparison, the Costa Rican government paid landowners $42 per ha per year to conserve forest areas. Other non-forest land uses earned $151 per ha per year (pasture area for beef cattle) and $825 per ha per year (sugar cane). But the value of the forest ecosystem is probably understated because it tracks incremental income only in one farm, whereas the forest must have benefited other nearby coffee farms.

    In our homocentric world, we try to measure the value of things by the way they impact our lives. It is not altogether an unfair measure, because it does give us a good idea of our place in the scheme of things. We can only hope that in the process, we also learn that there are aspects to the ecosystem which are greater than us.

    Taylor H. Ricketts, et al: PNAS , August 24, 2004, vol. 101, pg 12579–12582