Birds and other biodiversity

Birds and other biodiversity / Research on coffee growing

Research: Birds and lizards as insect predators in shade coffee

Borkhataria, R. R., J. A. Collazo, and M. J. Groom.  2006.  Additive effects of vertebrate predators on insects in a Puerto Rican coffee plantation.  Ecological Applications 16:696-703.

The authors used an exclosure study to see if birds and lizards had an impact on the abundance of insects in a shade coffee plantation, in particular two that damage coffee (the coffee leafminer and flatid planthopper).  When birds or birds and lizards were excluded, the abundance of larger insects increased.  In particular, planthoppers increased greatly when birds were unable to prey upon them. The leafminers, which are serious pests of coffee and are small insects, increased if lizards were not able to prey on them.   

This study indicates that birds and lizards (which the senior author found more abundant in shade coffee than sun coffee in Puerto Rico, presented in her Masters’s thesis) may help control the numbers of some coffee pests in shade plantations. Another important finding is that neither birds nor lizards interfered with the numbers of other natural insect enemies of coffee pests, parasitoid wasps.

Birds and other biodiversity / Certifications / Research on coffee growing

Research: Biodiversity, yield, and certification

Perfecto, I., J. Vandermeer, A. Mas, and L. Soto Pinto. 2005.  Biodiversity, yield, and shade coffee certification.  Ecological Economics 54:435-446.

The more complex overstory (and thus shade) in a coffee plantation, the higher the diversity.  However, the more shade, the lower the yield (although the relationship is not strictly linear), as coffee grows best in about 35-60% shade.  Therefore, farmers have to be compensated for the lower yields if they preserve shade and biodiversity.  Since a switch to organic farming typically increases yield, while a switch to more shade-dense farming decreases yield, the premiums paid to farmers for growing certified shade coffee must be higher than those for certified organic coffee.

This paper outlines the factors and decisions that have to be taken into account to determine best way to define certification criteria that will effectively preserve biodiversity while keeping yields high enough so that financial premiums paid to farmers are not so high as to discourage consumption. Of course, not all premiums have to be paid by consumers; aid and conservation organizations can absorb some of the costs.  And the authors seem to agree with others that linking shade-grown certification with Fair Trade and organic certification could be effective as long as the premiums are high enough to offset reductions in yield.

Background information / Birds and other biodiversity / Coffee and the environment

Birds and coffee plantations

Traditional, shade-grown coffee plantations harbor a diversity of many taxa — orchids, insects, and mammals, for example.  But it is the research that showed the importance of shade coffee plantations to birds that caught the attention of the public, and really kick-started the shade-grown coffee movement.

Over the last few decades, scientists noticed long-term declines in many species of Neotropical migrants — about 200 species of birds that breed in North America but winter south of the Tropic of Cancer. Researchers were prompted to examine the entire life cycle  of these species.  The ecology of the migrants on their nesting grounds here in North America was fairly well-studied, but more information was needed about the needs of these birds which spend most of their year in-transit or in the tropics. Searching for answers, researchers looked to the wintering areas of “our” breeding birds.

With so much habitat in the New World tropics being cleared for agriculture the importance of coffee plantations to wintering North American migrants (as well as resident species) soon became evident. The multi-layered vegetation of traditional or rustic shade-grown coffee plantations provides food and cover for birds which is in some cases very similar to native forest. In areas where farming has replaced natural habitat with stark pastureland and row crops, coffee farms are sometimes the only quality habitat available.

The Smithsonian Migratory Bird Center’s fact sheet, “Why Migratory Birds are Crazy for Coffee,” notes:

In the regions most heavily used by migratory birds — Mesoamerica, the Caribbean islands, and Colombia– coffee plantation “forests” cover 2.7 million hectares, or almost half of the permanent cropland.

In southern Mexico, coffee plantations cover an area over half the size of all of the major moist tropical forest reserves, providing critical woodland habitat in mid-elevation areas where virtually no large reserves are found.

Under the category “Research on coffee growing,” you can find summaries of some of the research on bird diversity on coffee plantations.  Some facts gleaned from this research include:

  • The majority of bird species in shade coffee plantations are feeding in the shaded overstory, not in the coffee.  The coffee shrubs themselves offer few resources.  This is why sun coffee monocultures do not support a diversity of birds.
  • The value of coffee farms is dependent largely upon the diversity of  their canopy: both the number of different species and the structural complexity of the canopy.
  • Invertebrates, fruit, and nectar are the most important food sources for birds in coffee plantations, so coffee farms are especially important to bird species that feed on these resources.
  • Migratory birds are more flexible in their habitat requirements, and do better in coffee plantations than many resident species, which are more sensitive to habitat changes.
  • Use of coffee plantations by migrant birds is highly seasonal.  Of course, North American migrants are only present in the tropics during spring and fall migration and in winter.  However, even during winter some migrants, in particular those that feed on nectar or fruit, tend to increase in number from early to late winter in plantations where these resources are available.  Three North American migrants are strongly associated with the flowering of Inga trees (which are commonly planted in shade coffee canopy):  Baltimore Oriole (above), Orchard Oriole, and Tennessee Warbler.

Bird diversity in rustic or heavy shade plantations sometimes rivals that of natural forests.  These plantations always have a significantly higher bird diversity (as well as a diversity of other species) than do sun coffee plantations. Shade coffee plantations offer important refuges for species in areas where natural habitats are quickly being converted to agriculture.

It is essential to understand the different degrees of shade under which coffee is grown, because some growing methods even if technically “shade grown,” are not beneficial to birds.

A summary of the eco/bird-friendly, sustainable coffee movement and its associated certifications is within the paper “In pursuit of sustainability: lessons from the coffee sector” by Robert Rice of the Smithsonian Migratory Bird Center.  Annotated PDF here.

Baltimore Oriole photo by Cindy Mead of Woodsong Nature Photography; used with permission.

Birds and other biodiversity / Research on coffee growing

Research: Shade grown coffee and orchids

Solis-Montero, L., A. Flores-Palacios, and A. Cruz-Angon.  2005.  Shade-coffee plantations as refuges for tropical wild orchids in central Veracruz, Mexico.  Conservation Biology 19:908-916.

This paper in the journal Conservation Biology reports that shade coffee plantations in Mexico provide refuge for orchids from lower montane cloud forest habitats — the most endangered forest type in the country, now comprising only 1% of Mexico’s land.

The magazine of the American Orchid Society published a similar article years ago:

Nir, M.A. 1988. The survivors: orchids on a Puerto Rican coffee finca.  American Orchid Society Bulletin 57:989-995.