This example highlights the need for locally and regionally specific research into the social–ecological causes and consequences of changing coffee production patterns.In addition to global and regional shifts in coffee cultivation, within-farm vegetation management has changed dramatically across centuries of coffee production. Farm-level coffee management involves distinctions in elevation, sun exposure, soil conditions, the density of bushes, the presence of additional wild or cultivated plants, the age of bushes and pruning style, and agrochemical use . The most traditional coffee growing practices, as seen in rustic coffee, involve growing coffee under a diverse canopy of native forest trees in high to moderate shade. As vegetation management is intensified, plantations have fewer shade trees, fewer shade tree species, lower canopy cover, and fewer epiphytes . Shade management intensification is often also accompanied by an increased use of synthetic agrochemicals . Finally, at the most intensified end of the vegetation management spectrum, coffee is grown in full sun. Interestingly, examining coffee vegetation management across a number of countries reveals that shade cover management is heterogeneous, and the changes in its coverage are region specific. In Latin America, between 1970 and 1990, hydroponic net pots nearly 50% of shade coffee farms were converted to low-shade systems . The changes varied by country, ranging from 15% of farms in Mexico to 60% in Colombia .
Since the 1990s, regions with intensively managed coffee, such as Brazil and Colombia, remain largely devoid of diverse-shade systems and have either maintained or increased their areas of sun coffee . From the 1990s to 2010, most Latin American countries decreased the percentage of total coffee production area dedicated to traditional diversified shade coffee production but at a slower rate than from 1970 to the 1990s. On the basis of the nine countries for which we have data from both the 1990s and the 2010s, we found that more than half of these countries experienced a decrease in the percentage of coffee under traditional shade management . However, because coffee production areas expanded in the remaining four countries and because these countries reported higher percentages of shade production, our calculations for Latin America suggest an increase in the area of land dedicated to diverse shade. However, a wider comparison of 19 countries for which we have 2010 data shows that approximately 41% of coffee area is currently managed with no shade, 35% with sparse shade, and only 24% with traditional diverse shade . This indicates that global shade coffee cultivation is lower than our estimates for 1996 , when approximately 43% of all coffee areas surveyed were cultivated in traditional diverse shade. For example, between 2000 and 2009, coffee-growing regions in Costa Rica experienced a 50% loss of shaded coffee in the process of conversion to sun coffee, pasture, or other crops . The sun coffee management style has also dominated many new coffee-growing regions, exemplified in Vietnam’s dramatic expansion of coffee and also evident in Thailand and Indonesia . In contrast, only a few countries have continued managing diverse shade since the 1990s in all or parts of their coffee regions . Coffee vegetation management patterns are nuanced and often depend on farm size, available alternatives, national and regional politics, risk-avoidance strategies, and development funding. For example, 81% of the coffee in Nicaragua and El Salvador grew under a shade canopy in 1996, and although recent surveys document declines in shade tree diversity since then, these declines mostly occurred on larger farms; in contrast, many smallholder cooperatives preserve high levels of biodiversity, including more than 100 species of shade trees on fewer than 30 farms .
Similarly, in the Kodagu coffee-growing region of India, nearly 100 tree species can still be found in smallholder coffee farms . Although it is clear that coffee management styles remain unevenly distributed both within and among countries, the causes for this high level of variation have never been systematically reviewed. We document several broad trends and posit that coffee vegetation management style is influenced primarily by five main factors: cultivar origin; perceived resistance to disease, primarily the coffee leaf rust; perceived increases in yield; socioeconomic decisions related to group membership and livelihoods; and shifting economic incentives linked to global coffee markets and value chains. Here, we present a comprehensive review of these five major factors and document the evidence supporting and contradicting each.The two globally dominant coffee species are C. arabica and C. canephora , which have distinct origins and cultivation histories and therefore differ in flavor, ideal growing conditions, resistance to pests and pathogens, and yield, among other traits. Although arabica and its cultivars grow best at middle to high elevations , exhibiting their maximum photosynthetic rate at moderate temperatures and higher shade levels, robusta and its cultivars are tolerant of lower elevation and full sun exposure and grow best at temperatures between 24 and 30 degrees Celsius . The distinctions between these species— their tolerance for temperature shifts, the development of disease resistant cultivars, and a number of socioeconomic factors described in this review—underlie much of the variations in current coffee vegetation management practices seen across the globe.Fungi cause most major coffee diseases and primarily affect C. arabica , whereas C. canephora varieties remain more resistant . Coffee leaf rust is the main disease of C. arabica in Latin America ; the latest outbreak lowered harvests by 10%–70% in several Latin American countries, including Peru , Mexico , Colombia, Costa Rica, Nicaragua, Honduras, Panama, El Salvador, and Guatemala .
Efforts to control coffee leaf rust in the 1970s and 1980s led to much of the modernization of coffee cultivation practices in Guatemala, Honduras, Panama, and other countries and include practices such as the use of supposedly disease-resistant, high-yielding varieties, the reduction of shade, and the increased planting density of coffee bushes . Although these measures were implemented to reduce coffee leaf disease, research has shown that disease dynamics depend on the specific disease, local fertilization conditions, humidity, elevation, temperature, and regional land management. Vegetation complexity may increase coffee leaf spot , brown eyespot , and coffee rust incidence, but with the latter two species, the specific cause of the increase is linked to humidity, not shade; rust incidence increases with humidity, independent of shade levels . In fact, moderate shade can actually reduce brown eyespot , weeds, and the citrus mealy bug and can increase the effectiveness of parasites of other pests . In addition, moderate shade levels can hinder fungal diseases by creating windbreaks and slowing the horizontal spread of coffee leaf rust spores . Therefore, coffee disease cannot be reduced by shade management alone, but it can in combination with modified humidity, predator management, and local and regional landscape management.The interactions among shade, yield, and the resultant coffee quality are very important to farmers, the coffee industry, and consumers. Yield-focused government incentives such as coffee research institutes, created in the 1970s and 1980s , promoted the reduction or removal of shade cover , created extension programs to support intensified practices, blueberry grow pot and financed programs that often included free or subsidized agrochemicals . Although many farmers cite increases in coffee yields as the main reason for removing shade trees and native vegetation, the ecological evidence supporting decreased shade and increased coffee yield is far from clear. Studies in which yield in low- and high-shade treatments have been categorically compared have shown lower yields with shade, higher yields with shade, and no difference; however, studies in which a continuous gradient of shade was examined have predominantly revealed that intermediate shade levels produce the highest coffee yield, which is probably because of the balance maintained between optimal temperatures in shaded environments and optimal photosynthetic rates in unshaded environments .
Although it is difficult to compare findings across studies because of geographical differences, it is clear that yield is not solely or linearly linked to shade tree density or diversity. Recent work has also shown that cup quality is the result of a variety of interacting factors that include environmental conditions, field management, adequate processing and drying, and roasting. Surprisingly, breeding efforts for coffee have largely ignored quality and have been focused mostly on increasing yields and disease resistance . Research related to shade effects on Catimor varieties points to shade’s positive effect on coffee bean and cup quality in lower elevations and effects on cup quality that can be either positive or negative at higher elevations . Shade appears to impart its greatest benefit in coffee bean flavor for plants growing in suboptimal and heat-stressed growing regions, where shade can bring environmental conditions closer to ideal levels . This suggests that shade may be particularly important for maintaining coffee quality in the context of climate change, especially in regions with expected temperature increases in future climate scenarios.Farm size, cultural history, and a farmer’s relationship with cooperatives can influence farmer management decisions and use of shade vegetation . In Veracruz, Mexico, small-scale producers used lower levels of agrochemicals per farm than did larger scale farmers , which resulted in fewer soil and water contamination problems. However, many of these small-scale farmers are slowly adopting several of the intensified management practices used by larger growers . In El Salvador and Nicaragua, small , individually managed farms contained higher levels of shade tree diversity than did larger collectively managed holdings ; furthermore, tree diversification levels were highest for cooperatives that clearly defined who would benefit from shade tree products . In both of these countries, individually managed farms adopted vegetation diversification in order to generate a wider variety of tree products and on-farm benefits . These farmers managed their coffee plantations both for household consumption products and for income from coffee. In contrast, collectively managed farms are focused almost entirely on producing coffee for income, partly because of the challenge of distributing both the work and the benefits to obtain more on-farm products. The only non-coffee product on which collective farm members are dependent and actively collect is firewood; collective cooperatives have an open policy for their members to aquire firewood for household use . Therefore, well-organized cooperatives, if they are present, can be essential for coordinating collective action that can help smallholders manage the distribution of benefits and retain land titles , which potentially creates key institutional environments for sustainable land stewardship. In addition to land titles, a number of assets are important for optimal livelihood: participation in a cooperative or other local associations and access to land, water, loans, houses, and equipment . Research shows that individuals working at the production end of the coffee value chain continue to receive a very small fraction of the profits . Coffee pickers and laborers are the most marginalized actors within the coffee value chain , because they are vulnerable to shifts in production, climate, and market demands and are paid by the pound or volume of coffee cherries harvested, making as little as $2 per day in many parts of the world . For example, between 2000 and 2001, Ugandan farmers received $0.14 for a kilo of unprocessed coffee that at retail would fetch more than $26.00 as instant coffee in the United Kingdom . Accounting for weight loss during the processing and roasting of the coffee, this represents a 7000% price increase in the journey from farm to shopping cart . Other cases are less lopsided; Colombian farmers received 23%–25% of the value added for coffee sold into specialty and mainstream markets in 2010 . However, although specialty coffees often result in higher prices at the farm gate, questions remain about the extent to which the benefits of higher retail prices translate into higher revenues for farmers and communities . Broad-based job losses in coffee farming have decreased since 2005, but seasonal hunger, marginalization, and other vulnerabilities persist .One avenue to address declines in coffee profits and sustainable management is the specialty coffee market, which currently claims 37% of coffee volume but nearly 50% of the coffee value in the 2012 US coffee market, worth an estimated $30 billion to $32 billion .