Coffee Leaf Rust, a plague affecting coffee plants worldwide, appears to worsen when coffee is grown in full sun, according to recent research published by the University of Michigan (conducting their research in Mexico). Shade-grown coffee has been making a small comeback for the more environmentally conscious caffeine consumer. Shade-grown coffee means more habitat for birds and other forms of biodiversity; it means coffee growing does not have to be synonymous with deforestation. Shade-grown coffee can also be a reservoir for genetic diversity and reduce the impacts of habitat fragmentation. This type of coffee cultivation is how coffee around the world was grown prior to 1970. But in the 70’s, the increased yields of growing coffee in full sun came to light (no pun intended). Since most farmers look at total yield as a measure of success (a common sense thing to do!), many switched to that method. Additionally, by only having coffee trees, mechanical aids or other tractor-type equipment could maneuver easier among the trees.
But 1970 was a momentous year for coffee for another reason, one that was not as widely publicized. This was the year that coffee rust made its debut in Latin America. The rust was first discovered near Lake Victoria in eastern Africa in 1861, and formally identified and studies in Sri Lanka in 1867. The plague slowly spread until it reached Bahia, Brazil in 1970 and quickly found its way to Central America. The rust is damaging coffee plantations, causing major foliage loss and even death of the trees. And the plague was only been on the rise. According to recent statistics, coffee harvests in Guatemala and El Salvador are down 34 and 40 percent, respectively, compared to the same harvest period one year ago. This decline has been linked directly to reduced production from trees affected by the leaf rust. Central America provides 14 percent of the world’s coffee, and so a repeatedly decline in harvest could potentially cause world coffee prices to rise, particularly if other countries are struggling with the rust as well.
The study out of Mexico (by way of the U. of Michigan) indicates that farmers would do well to shade their coffee trees again. But growing trees to shade coffee (which generally measure between one and two meters tall) will take several years. Patience will be needed to resolve this problem, as the rust has proven immune to pesticide treatments or other “quick-fix” cures. Keeping the ground litter cleared, replacing affected trees immediately – these are other methods to help prevent the spread, but they are not cures. Bringing back shade grown coffee will be another tool in the toolbox that farmers can use to try to overcome this plague. In the mean time, scientists will continue to experiment and search for varieties resistant to the rust, or other methods of rust control. Hopefully, though, the increase in biodiversity in coffee plantations will bring about a natural cure. Monocultures have never been strong, why would coffee be any different?