Coffee flower phenology changes and pollinator response in strong el niño year

Background/Question/Methods

Upland coffee, coffea arabica, is the second most valuable commodity exported by developing nations.  Cross-pollination of coffee increases initial seed set and research indicates that initial seed set increases with an increasing diversity of native bees.  In the seasonally dry premontane forests of the pacific slope of Central America, coffee flowers in several two to three day flowering periods between February and May.  These flowering periods are comprised of two or three small blooms and one mass bloom, which draws in large numbers of the non-native honeybee, Apis mellifera.  In strong el Niño years, coffee flowering phenology changes to several small blooms and two mass blooms, occurring earlier and later than the typical one mass bloom. Strong el Niño years may be the best proxy for understanding future climate change conditions in the region.  In the recently passed strong el nino year of 2009, I documented the coffee flowering phenology, the pollinator community and coffee production response, comparing to previous ‘typical’ years in the same region.

Results/Conclusions

In 2007 and 2008, the single mass bloom occurred in April.  In the strong el Niño year of 2009, one mass bloom occurred in early March due to the abnormally high amount of rainfall during the dry season and a second mass bloom occurred in early May due to the late onset of the rainy season.  Smaller blooms prior to the mass blooms in 2008 and 2009 had similar bee species richness to the mass blooms of 2007, 2008 and the first mass bloom in 2009. Species accumulation curves for bee visits to coffee flowers during the different bloom periods indicate that bee species richness nearly tripled in the second mass bloom period of 2009, from a mean of 11 ± 1.78 bee species in all small and mass blooms of 2008 and 2009 to 26 ± 4.41 in the second mass bloom in May 2009.  Bee abundance, measured in bee visits to coffee flowers, showed similar differences among the bloom periods.  Coffee production was significantly higher in the strong el Niño year, however this was due to the drier rainy season and the two mass blooms, and was not due to higher initial seed sets from the increase of bee species richness.  However, it is likely that these coffee farms benefitted in production from the strong el Niño year climatic conditions only because they were shade-grown coffee farms.