Exactly a year ago yesterday Jeremy wrote a post about the dollar value of pollination as an ecosystem service. Now comes an article in Gaia which argues that previous criticism of such valuations in the same journal are unfounded. ((Alexandra-Maria Klein, Roland Olschewski and Claire Kremen. 2008. The Ecosystem Service Controversy: Is There Sufficient Evidence for a “Pollination Paradox� GAIA 17/1:12–16.)) A year is a long time in science.
The criticism in question was based on the observation that “crops depend on pollinators but crop yield does not necessarily depend on pollinators as other factors are likely to limit crop production.” Jaboury Ghazoul called this the “pollination paradox” ((Ghazoul, J. 2007. Recognising the complexities of ecosystem management and the ecosystem service concept. GAIA 16/3: 215–221.)) in an article which argued that it is impossible to value ecosystem services individually.
The authors of the latest paper dissect the situation with coffee and almond and conclude that “there is currently no evidence for a pollination paradox.” However, they do say that recent figures for the monetary value of pollination may well be media-driven overestimates. Even the often-seen figure that “one third of the caloric value of our food is derived from animal pollination … is still not well supported.” That pollinators are important to food production is not contested. But how important is perhaps not as easy to calculate as has been made out.
There is another pretty interesting article about pollination services that has been published this week online in Ecology Letters by Ricketts et al.: “Landscape effects on crop pollination services: are there general patterns?”
Here are a few ‘teaser’ quotes from the abstract:
“Using hierarchical Bayesian techniques, we synthesize the results of 23 studies – representing 16 crops on five continents – to estimate the general relationship between pollination services and distance from natural or semi-natural habitats. We find strong exponential declines in both pollinator richness and native visitation rate.”
“Evidence of general decline in fruit and seed set – variables that directly affect yields – is less clear. Visitation rate drops more steeply in tropical compared with temperate regions, and slightly more steeply for social compared with solitary bees. Tropical crops pollinated primarily by social bees may therefore be most susceptible to pollination failure from habitat loss.”
Full citation:
Taylor H. Ricketts, James Regetz, Ingolf Steffan-Dewenter, Saul A. Cunningham, Claire Kremen, Anne Bogdanski, Barbara Gemmill-Herren, Sarah S. Greenleaf, Alexandra M. Klein, Margaret M. Mayfield, Lora A. Morandin, Alfred Ochieng’, Blande F. Viana (2008) Landscape effects on crop pollination services: are there general patterns? Ecology Letters 11 (5) , 499–515 doi:10.1111/j.1461-0248.2008.01157.x