Pesticides have an impact on the agricultural frontier of Amazon

The "ecological footstep" of the compounds is increasing, according to a study that evaluated the usage standards of large and small producers. The article was published by the Royal Society.

By Elton Alisson

Agência FAPESP – Small producers along the Brazilian Amazon’s agricultural frontier are using pesticides in higher doses and at greater frequencies than are recommended, and in some cases, chemicals are being used that are inappropriate for the infestations that they are intended to control. The large soybean and sugarcane producers in the region follow more of the prevailing agronomical recommendations and even replace compounds that are more toxic to human health with other, less harmful inputs.

However, the study indicates that the risk of the adverse effects of pesticides on aquatic species, such as fish, has increased significantly. This is because, with the intensification of agriculture on the Amazon agricultural frontier, the pesticides are being applied at higher doses, and although they are less toxic for humans and other mammal species, they may be harmful to smaller organisms.

The study was conducted by researchers at the Universidade de São Paulo’s School of Arts, Sciences and Humanities (EACH-USP), in collaboration with colleagues from the Institute of Biological Sciences at the Universidade Federal do Amazonas (Ufam), the Department of Biomedical Sciences at the Vienna University of Veterinary Medicine in Austria, and the Alterra Institute of Holland.

The results of the study, developed under the auspices of a FAPESP-funded project, were included in a thematic special volume on the Amazon’s agricultural frontier, published by the Philosophical Transactions of the Royal Society.

“We observed that the small producers on the Amazon agricultural frontier make gross and uncontrolled use of pesticides, while although large producers in the region have followed technical recommendations and voluntarily substitute toxic inputs with less harmful substances, the ‘ecologic footprint’ of these compounds increased over time,” said Luís César Schiesari, professor at EACH and the first author of the study.

The researchers analyzed the pesticide usage standards of producers with different risk profiles on the Amazon agricultural frontier and the potential risks of use on biodiversity in the region.

To this end, beginning 2005, the team conducted interviews with 220 small fruit and vegetable producers from four cities in the central region of Amazonia in the flooded forest of the Solimões River and with the managers of an 80,000-hectare soybean farm in Mato Grosso on the border with Amazonia and another 60,000-hectare property located on the Negro River that is in the process of being converted to a sugarcane crop.

The pesticide application data provided by the producers themselves revealed that 96% of small farmers applied substances to their crops in higher doses and at greater frequencies than those recommended.

The large producers follow technical recommendations more closely and even reduce the usage of compounds that are harmful to humans and the environment, according to the toxicological and environmental risk classification adopted by the Health and Environment ministries.

On the other hand, the number and dosage of pesticides utilized has increased – which has increased the risk of damage to certain species of animals, according to researcher observations based on a series of calculations conducted to measure the size of the ecological footprint of agricultural inputs to the biodiversity of the region. “We found that an increase in the dose and diversity of pesticides utilized by large producers caused a drop in the risk for mammals that inhabit these environments,” explained Schiesari.

“In contrast, the risk for aquatic organisms increased 135 times, according to calculations based on the toxicity data of pesticides for algae, fish and zooplankton [small animals that live in suspended aquatic environments],” he affirmed.

According to Schiesari, one of the explanations for this difference is that the categorization of these compounds with respect to the possible impacts on human health is conducted using laboratory rats. Therefore, the risk classification system is only valid for mammals.

“The risk of toxicity presented by a certain pesticide, however, could greatly vary from one organism to another. A less harmful compound for rats does not necessarily present risks for fish, birds and insects,” he explained.

More susceptible areas

According to Schiesari, the agricultural frontiers (regions of conversion of natural habitats for agriculture) are the areas that are most susceptible to environmental impacts. This is because, as these areas are concentrated in tropical forests—characterized by large biodiversity—they are environments in which there is a greater number of species that have not yet been exposed to the risks of potentially harmful land management techniques, such as indiscriminate use of pesticides. They are therefore more vulnerable to environmental contamination, for example.

“In traditional agricultural landscapes, many species have been lost, and the remainder may present some level of evolution in their tolerance for environmental contamination not only by pesticides but also by heavy metals,” said Schiesari. “In the case of agricultural frontiers, this does not occur, because there are more diverse fauna and flora without previous contact with damaging agricultural practices.”

The researchers argue that agricultural frontiers receive greater attention in terms of actions focused on promoting more sustainable handling practices through regulation and controlled use of substances.

Schiesari explained that pesticides, recognized as important tools for agriculture because they permit increased agricultural productivity, are formulated to have a biological effect on agricultural pests but can harm other species by affecting the basic physiological mechanisms common to several organisms. “Many pesticides have action mechanisms that consist of acting on physiological processes that are common to a vast number of organisms—for example, cellular respiration, transmission of neuronal impulses and formation of fuses that separate chromosomes in cellular division. In this manner, they can have impacts on several organisms that are completely unrelated to the pest the agricultural input intends to control,” he said.

The article “Pesticide Use and Biodiversity Conservation in the Amazonian Agricultural Frontier” (doi: 10.1098/rstb.2012.0378), by Schiesari and others, can be read in the Philosophical Transactions of the Royal Society at rstb.royalsocietypublishing.org/content/368/1619/20120378.short?cited-by=yes&legid=royptb;368/1619/20120378.