Subject: Sun v. Shade Coffee
Date: Mar 25 12:05:37 1997
From: Kelly Cassidy - kelly at cqs.washington.edu


Just to complicate the coffee debate:

There is a letter to the editor in the March 14, 1997 Science
(magazine), (volume 275, page 17) regarding sun v. shade coffee. It's
written by Charles MacVean, who gives his address as Institute of
Research, Universidad del Valle de Guatemala. He is writing in
response to an artical concerning the benifits of sun v. shade.

He begins by saying that sun plantations of _Coffea arabica_ are prone
to massive tree death during drought, though some localities have
sufficient cloud cover, etc., that tree death rarely occurs. _Coffea
robusta_ is more tolerant of high light and drought. (He doesn't
indicate which species is most likely to be used in Folgers or
Starbucks.)

He goes on to write:

"The question of labeling coffee as "environmentally friendly" is also
tricky. Open-sun plantations are structurally and biologically
depauperate, and they require much higher agrochemical inputs
(primarily fertilizer) than traditional shaded coffee. It may be true,
as Robert Rice speculates, that a plantations with a single species of
shade tree and heavy pesticide use is no more friendly than a sun
plantation. But the main difference in agrochemical use between sun
and shade plantations is not in pesticide, but fertilizer use.
Herbicide use also increases with the degree of sun exposure becuase of
increased weed growth, and chemical elimination of flowering plants can
affect nectar-feeding arthropods more than conventional manual
weeding. Arthropod diversity and herbivore pressure on coffeee are
notoriously low relative to what occurs in the shade tree canopy
(MacVean and Greenberg, unpublished observations).
Even in plantations with just one or two species of shade tree (Inga
spp., for example) we have found most of the arthropod prey base for
birds concentrated in the overstory. Chemical applications occur in
the coffeee shrub understory. On the other hand, soil-dwelling species
such as the cicada numphs mentioned by Young (Letters 3 Jan. p. 12) or
the larvae of scarab beetles are at risk, and these may be significant
food resources for birds. The ecological intricacies of coffee
management systems must be studied with sound quantitative methods
before generalizations about "friendliness" can be made."