by Russell Greenberg and Robert Rice
This document is a summary of minimum shade management practices necessary on a coffee plantation for the SMBC to consider that plantation sustainable. Because coffee is grown under diverse management systems and climatic and ecological conditions, the criteria have been designed to be as general as possible. Our field work has focused on the northern Neotropics and we have limited knowledge or experience with shade systems in the Old World.
Therefore, further research will be required to extend some of these bio-physical criteria to Old World systems. In addition, further research is required to develop recommended practices that, above and beyond the minimally acceptable management practices for farmers, would enhance the biodiversity of coffee plantations and maintain socio-cultural benefits of the shade complex.
Coffee is grown under two types of shade: Rustic shade, which consists of natural forest vegetation, and planted shade.
Rustic shade consists of natural forest species. Rustic coffee can consist of coffee grown under old growth, or more commonly, secondary forest. Where additional trees have been planted to produce useful products, the system is called Traditional Polyculture. The area of coffee grown under such systems varies from place to place, but, from the standpoint of bird conservation, the maintenance of such systems is highly desirable.
Two major issues arise: the degree of management and the potential protected status of forest used for shade. Even in rustic or traditional systems, shade trees are generally thinned and trimmed to reduce understory humidity and increase light levels. The SMBC recommends that a minimum canopy cover of 40 percent be maintained and that no trimming of epiphytic plants or hemi-epiphytic vines be conducted on the shade trees. Vines and unwanted plants on coffee plants, of course, should be removed for production purposes. We further urge that farm inspectors verify that forest converted to coffee production does not have any legal protected status.
Planted-shade plantations generally consist of a backbone of trees which are the predominant species planted to provide the optimal shade environment for the coffee plant. In New World systems the most common backbone trees are Inga spp. and, at lower elevation and latitude sites Erythrina spp. Less common backbone trees are Gliricidia sepium and Grevillea robusta. From the consideration of biodiversity conservation, Erythrina and Gliricidia are unacceptable as backbone species because they are deciduous during the dry season leaving the "shade" plantation shadeless during a time of the year when canopy cover for both migrant and resident birds may be most critical.
Grevillea is unacceptable for two reasons. First, it is non-native and therefore probably supports few native species of arthropods. Second, although it supports high densities of birds, the diversity is the lowest of all types surveyed by the SMBC. Additional types of trees occasionally used as backbone species include Albizia spp. and Pinus spp. These species support few insectivorous birds and are often introduced from other regions and are therefore not acceptable. Erythrina, Grevillea, and Gliricidia are all used by birds—particularly the flowers of the first two—and are an acceptable part of the canopy at low density (less than five percent canopy cover).
Numerous species of Inga are used for shade. Individual farms commonly have three or more species, each with its own pattern of flowering phenology. It is important that several species are used to maximize the period when Inga flowers and fruit are available. SMBC recommends that, on a given coffee farm, a single species of Inga does not comprise more than 50 percent of the Inga trees.
The number of species of birds and other organisms will increase with increasing diversity of trees in a plantation. We recommend that no more than 70 percent of the canopy cover consist of Inga. For general criterion it is impossible to specify the composition of the additional trees since this will vary regionally. Future research should provide the information to develop a list of recommended trees that are of value to both birds and people for different regions.
Coffee plantations can be ranked by the total number of tree species per hectare, provided that inspectors are sufficiently well trained in the identification of common trees of agroforestry systems in the region. The diversity of potential supplementary shade trees will vary with region (lower on Caribbean islands, and sites at higher elevations and latitudes). However, we suggest a minimum of ten species of trees to qualify for certification as "Bird Friendly®".
Biological diversity probably increases with the amount of canopy cover. However, coffee is not necessarily a full-shade plant. As a compromise between these considerations, SMBC recommends a minimum shade cover of 40 percent at solar noon that can be estimated or measured with an optical densiometer. The shade cover measurement cannot include that produced by coffee plants themselves. The shade cover should not be reduced below the 40 percent minimum even after pruning. Pruning should be conducted during the rainy season.
Probably more critical for biodiversity, at least avian diversity, is the stature of the canopy trees. We recommend that the backbone shade species be allowed to attain a minimum of 12 to 15 meters in height. In the case of newly established farms in transition to full shade conditions, inspectors should be sensitive to pruning practices that would prevent trees from achieving these heights.
It is well known that vertical structural diversity results in increased bird diversity. Therefore, farmers should be encouraged to plant trees that are shorter and taller than the backbone shade species. Taller trees can include timber-producing species and shorter trees can produce fruit, medicines or other products. As a rule of thumb, lower and higher strata should each total at least 20 percent shade cover, in addition to the shade cover provided by the backbone species.
Epiphytic plants, such as bromeliads, and parasitic plants, such as mistletoes, contribute considerably to overall biological diversity and provide resources for birds. The growth of these plants on canopy trees should be encouraged. Although the expected amount of epiphytic growth varies between regions with different climates, we would recommend that inspectors compare coffee canopies to remnant natural vegetation or visit farms during periods of pruning to determine if epiphytic growth is being systematically removed. In addition, pruning should ideally leave some dead limbs and snags.
A "living fence" or border strip of trees and shrubs should be maintained along roadways and other borders to prevent the desiccation of the understory due to wind. In addition, a strip of natural second-growth vegetation should be maintained at a width of five meters from each side of small streams and ten meters along rivers.
In addition to the above specific considerations, inspectors should have a sheet with schematic diagrams showing alternative structures of coffee plantations. One such system, modified from a system developed for Mexico, is attached.
|Rustic to Traditional Polyculture|
We recommend that farms that have a structure that resemble the diverse commercial polyculture, traditional polyculture or rustic systems be certified as "Bird Friendly®". The less diverse commercial polycultures, characterized by low stature or low species richness, will not be acceptable as "Bird Friendly®".
(Note: This summary of shade criteria for "Bird Friendly®" coffee has been developed by the Smithsonian Migratory Bird Center in the spirit of cooperation and mutual interest with others involved in coffee (producers, traders, retailers, researchers, etc.) who share concerns for this very important aspect of sustainable coffee. We urge anyone to make use of these criteria in whatever way(s) he or she sees fit. Comments on particular details are also welcome, and should be sent to us via Email. For legal reasons beyond our control, any use of the name "Smithsonian" or the term "Bird Friendly®" or reference to them on a commercial product or for commercial activity is forbidden. In addition, any reference to the National Audubon Society and the shade criteria for commercial purposes is not allowed.)
|Canopy height||At least 12 meters for the canopy formed by the backbone species|
|Foliage cover||At least 40%, ideally measured during the dry season and after pruning when deciduous species have dropped their leaves and cultural practices have minimized foliage presence.|
|Diversity of woody species (trees and shrubs)||At least 10 woody species (in addition to the backbone species), with at least 10 of these representing 1% or more of all individuals counted in the inspector's sample, and dispersed throughout the production area.|
|Total floristic diversity||The sum of all species observed in the inspector's sample—both woody and herbaceous species. Other than the criterion for woody species (above), no minimum for total floristic diversity. Herbaceous species noted in sampling—often as ground cover—but not critical in attaining certification.|
The "architecture," or profile, of the shade should reveal obvious layers or strata of foliage-preferably 3. The layers are:
|Leaf litter||As in organic standards, it should be present.|
|Herbs or forbs on ground layer||Should be present; no specific amount stipulated.|
|Living fences||Where appropriate, these should be present.|
|Vegetative buffer zones alongside waterways||Should exist and be composed of native vegetation. For creeks and small streams, at least 5-meter swath on each side is required; for rivers, the buffer should be at least 10-meters wide on each side.|
|Visual characterization ("Geshtalt")||Along the shade gradient, it should at least fall into the category of the more diverse commercial polyculture. (See Figure 1.Top 2 images below would be considered "Bird Friendly®".)|
|Organic certification||Must exist and be current from a USDA accredited certification agency.|