robusta coffee to the world market, the battle against rust had
another important consequence for coffee agriculture -- the widespread
conversion of plantations from shade to full sun. Cultivators believed
that drier conditions would prevent the fungal rust from spreading.
At the same time, they discovered that growing coffee in sunshine
could increase short-term productivity, as long as they increased
their applications of pesticides and fertilizers to help sustain
the increased yields.
In most Latin American countries outside of Brazil, coffee has traditionally
been grown under a shady forest canopy. The trees provide a microclimate
favorable to coffee -- reducing the range of temperatures on the
plantation and offering shelter from wind, storms, and overexposure
to sun. (While full sun increases yields in the short term, it depletes
the soil over time.) Additionally, nitrogen-fixing trees of the
forest keep the soil rich in nitrogen, a critical nutrient. Leaves
and other detritus create a natural mulch that keeps the soil fertile
and reduces erosion. Although growing coffee in the shade is labor-intensive,
requiring weeding and harvesting by hand, it reduces the need for
large-scale applications of synthetic fertilizers and pesticides.
"Sun-coffee" plantations need continual inputs of pesticides
and fungicides to control biological enemies that thrive in coffee
monocultures, as well as nitrogen fertilizers to replenish exhausted
soil. Removing the forest's network of roots and natural mulching,
increased erosion becomes a problem as well.