Crop damage by vertebrates in Latin America: current knowledge and potential future management directions

Abstract

Background: Crop farming contributes to one of the most extensive land use activities in the world, and cropland areas continue to rise. Many vertebrate species feed on crops, which has caused an increase in human-wildlife conflicts in croplands. Crop-feeding damages the economy of local communities and causes retaliation against the responsible vertebrates in several forms, including lethal practices such as hunting and poisoning. Lethal control may cause the local extirpation of some species, affecting ecological processes and patterns. Therefore, it is necessary to find non-lethal alternatives that can protect both local economies and wildlife. Research has been conducted in Africa and Asia, focusing on elephants and primates, and the effectiveness of some non-lethal alternatives, such as chili-based repellents and beehives, is being investigated. However, there has been very little research on this topic in Central and South America. The goal of this review is to assess the current knowledge on crop damage by vertebrates in Central and South America and indicate future research directions.

Survey methodology: We reviewed the available scientific literature reporting crop damage by vertebrates in Central and South America, and the Caribbean, published between 1980 and 2020, through systematic searches on Web of Science, Scopus, and Google Scholar. We analyzed the temporal and geographical distributions of the studies, the crops and vertebrate species these studies considered, the crop protection techniques used, and their effectiveness.

Results: We retrieved only 113 studies on crop damage by vertebrates in Latin America, but there was an increasing trend in the number of studies published over time. Most of the studies were conducted in Brazil, Argentina, Mexico, and Costa Rica. Four orders of mammals (Rodentia, Carnivora, Artiodactyla, and Primates) and four orders of birds (Passeriformes, Columbiformes, Psittaciformes, and Anseriformes) were the most common groups of crop-feeding vertebrates. The most prominent crop was corn, which was featured in 49% of the studies. Other notable crops include rice, sorghum, and sugarcane. The most reported method for protecting crops was lethal control through hunting or poisoning. Non-lethal techniques were found to be less prevalent. Less than half of the studies that mentioned the use of protection techniques indicated their effectiveness, and only 10 studies evaluated it by performing scientific experiments and reporting their results.

Conclusions: Central and South America is still underrepresented in research on vertebrate crop-feeding. There is a need for experimentation-based robust research to find crop protection techniques that minimize harm to vertebrates while effectively reducing damage to crops. While this is being studied, habitat loss and fragmentation need to be halted to prevent the native vertebrates from turning to crops for food.

Keywords: Agri-environment schemes; Animal damage; Bird damage; Crop feeding; Crop protection; Human-wildlife conflict; Mammal damage.

Figure 1. PRISMA flow diagram for the systematic review included in the analyses.

Figure 2. Annual number of studies on crop damage by vertebrates in Latin America from 1980 to 2020.

The color gradient is proportional to the number of studies in each year. The blue line depicts the trendline and the shaded area represents the 95% confidence interval.

Figure 3. Spatial distribution of studies on crop damage by vertebrates in Latin America.

The white circles represent the locations of the study sites for each article. The magenta areas represent surface covered by crops.

Figure 4. Importance value of the vertebrate orders represented in the studies.

The importance value was calculated by counting the number of taxa of each vertebrate order featured in each article and then summing the totals. Mammal, bird, and reptile orders are represented in purple, yellow, and green, respectively.

Figure 5. Network of interactions between vertebrate orders and crop genera found within the 113 studies included in this review.

Each article in which a vertebrate order was documented to cause damages to a crop genus is counted as one interaction. The width of the nodes is proportional to the number of interactions that each crop genus or vertebrate order had in total. Similarly, the width of each link is proportional to the number of interactions of its particular pair.

Figure 6. Number of studies that used or mentioned each type of crop protection technique.

Grey color on the bars represents the proportion of studies that did not determine the effectiveness of the protection techniques, magenta represents the proportion of studies that determined the protection techniques to not be effective, and green represents the proportion of studies that determined the protection techniques to be effective.