It’s immediately clear to anyone visiting the Greater Antilles that humans have had a dramatic impact on natural environments. Even in those areas that remain forested and seemingly pristine, it isn’t difficult to find the stray coffee bush or mango tree. Indeed, some understory crops, such as coffee and cacao, have traditionally been grown under an intact canopy. These traditional practices have been changing over the past few decades, however, as large commercial operations have favored the efficiency of clear-cutting and subsequent cultivation in open sun. The impacts of this shift from shade to sun cultivation on biodiversity have been debated for decades, with most studies indicating overall losses in biodiversity and super-abundance of a few common species in sun plantations.
In spite of the prevalence of agriculture in the Greater Antilles, relatively few studies have investigated the abundance of anoles and other lizards in different types of agriculturally disturbed habits (but see my first first authored paper!). A new study by Borkhataria et al. (2012) conducts a comparative analysis of species abundance of birds, anoles, and invertebrates in shade versus sun coffee on Puerto Rico. This study is a welcome addition to the literature because the portion of coffee on Puerto Rico grown in sun plantations has doubled in recent years, although overall coffee production has declined.
Borkhataria et al. (2012) use Heckel and Roughgarden’s classic mark-resight approach involving tree-marking spray paint guns and latex paint. Using this technique, an observer sprays anoles in a pre-defined area with paint over a period of three or four days, using a different color paint each day. By counting the number of lizards painted, or repainted, across the study, one can obtain reasonable estimates of anole density.
Borkhataria et al.’s (2012) results won’t surprise anyone who’s familiar with the Puerto Rican anole fuana: “Anolis cristatellus and A. stratulus were significantly more abundant in sun plantations whereas A. gundlachi and A. evermanni were detected more frequently in shade plantations.” You need to look at their Table 2, however, to get a better since for what exactly is going on. Three species are relatively common in both types of coffee: Anolis cristatellus is the most common anole in both shade (0.04/m2) and sun (0.06/m2) coffee, A. krugi is present at similar densities in both types of coffee (0.01/m2), and A. stratulus is twice as common in sun (0.2/m2) as in shade (0.01/m2). Thus, even those species that appear to do better in sun plantations are still relatively abundant in shade. The same cannot be said in the opposite direction: A. gundlachi and A. evermanni are all but eliminated from sun coffee with the number of observed individuals dropping from 525 to 2 and 241 to 6, respectively.
Borkhataria et al. (2012) conclude their abstract by stating that their “findings confirmed that shade plantations harbor a wide array of elements of biodiversity; but sun plantations may also harbor many elements of biodiversity, and in some cases, in higher abundance than in shade plantations.” For the anoles, however, the results seem to rather unambiguously support the notion that diversity will be lost in association with a transition from shade to sun cultivation of coffee.
- JMIH 2014: Early Records of Fossil Anolis from the Oligocene and Miocene of Florida, USA - August 13, 2014
- JMIH 2014: Relative Contribution of Genetic and Ecological Factors to Morphological Differentiation in Island Populations of Anolis sagrei - August 7, 2014
- JMIH 2014: The Ultrastructure of Spermatid Development within the Anole, Anolis sagrei - August 5, 2014
Liam Revell
Hi Rich. Great review of this article.
I can’t help wondering what the authors would have found if their survey methods had included techniques suitable for finding the elusive twig anole, Anolis occultus.
Your comment that “coffee production on Puerto Rico has increased dramatically in recent years, with most gains involving sun grown coffee” seems at odds with the authors’ other article, Borkhataria et al. (2012), from an earlier issue of the same journal. There they surveyed data from 1982 to 2007 and found that the total land area dedicated to coffee production in Puerto Rico fell from about 32,000 hectares in 1987 to only about 15,000 hectares in 2007. The fraction of coffee producing land on which non-shade coffee is grown increased from 1982 (20%) to 2007 (69%), but the real increase in land area for non-shade coffee was only modest (+4,000 hectares – offset, of course, by a total decline in land use for coffee of about 17,000 hectares). Of course, non-shade coffee yields more per hectare and I have not done the requisite calculations to figure out if total coffee production has increased or decreased (Puerto Rico remains a net importer of coffee, so far as I know).
Since more than 1/2 of the acreage dedicated to growing coffee has been abandoned (at least for coffee production) since 1982, another interesting question is what happens to shade & non-shade coffee plantations after abandonment? It seems possible that shade coffee left fallow might convert back to montane rainforest very rapidly. By contrast, non-shade plantations, already cleared, might be re-dedicated to other crops (such as bananas) or other non-agricultural uses; and even if the land is totally abandoned it may take many decades to recover.
– Liam
Rich Glor
Thanks for catching this mistake Liam. I was obviously reading into the first paragraph of the paper where they said “coffee comprises
approximately one-fifth of the total market value of all crops in
the island, and was valued at approximately $41.8 million in 2007
(USDA, 2009). The amount of land devoted to shade coffee has
decreased by 82% between 1987 and 2007, while sun coffee production
nearly doubled (Borkhataria et al., 2012).”
Liam Revell
My impression is that coffee is not very profitable in Puerto Rico due to the high labor costs relative to other coffee belt countries (at least in part due to U.S. minimum wage laws). Consequently, the coffee industry persists at a boutique level and through government subsidies. In many municipalities of the central mountains not only are coffee and agriculture generally in decline, but human population density is also falling. (The population of Maricao, for instance, fell by 23% in the 20th century; while the population of Puerto Rico increased nearly 300%, mostly in coastal areas.)
An interesting question regarding land use & conservation is as follows. If a farmer has 100 acres, and non-shade coffee yields is (say) four times as productive per acre as shade coffee, should a government motivated by conservation incentivize the farmer to plant 100 acres in shade; or clear 25 acres for sun coffee and leave the remaining land untouched? (My guess is that it depends on the species and/or specific conservation goal.)
Rich Glor
I’m always amazed at how little consideration people give to the fact that large trees and forests take decades to grow. Whatever decisions are made, I hope they’re being made only after making some long-term economic and environmental projections. I’m reminded of the disastrous post-WWII efforts to grow rubber trees in Haiti that resulted in the destruction of hundreds of thousands of fruit trees. The natural rubber market then promptly collapsed and Haitians were left without some of the fruits they had come to rely on. I realize the two situations are very different in both scope and consequences, but the common thread is that destruction of trees for short-term economic benefit can backfire.