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Glyphosate leaves its mark even in protected areas of Brazil’s Cerrado

  • A study found lichens dying as a result of exposure to glyphosate in an ostensibly protected area in Brazil’s Goiás state.
  • Formed by interaction between fungi and algae, lichens are bioindicators of air quality.
  • Glyphosate is the top-selling herbicide in Brazil and the world, used intensively in soybean, corn and sugarcane plantations; around 70% of pesticides sold in the country are applied in the Cerrado grassland biome.
  • The study confirms the dispersion of the product into conservation areas from farmland, with aerial spraying a major factor for this so-called drift.

Breathing clean air in Brazil’s Cerrado grassland has become increasingly hard, according to a recent study by researchers in the central state of Goiás. It found a relationship between dying lichens and exposure to glyphosate, a herbicide commonly used against weeds.

Lichens are organisms formed by fungi and algae that interact with each other. The fact that they’re dying off in the presence of glyphosate “this indicates poor air quality,” said study co-author Luciana Vitorino, a microbiologist at the Goiás Federal Institute. “In tropical forests, as is the case, the presence of lichens indicates good atmospheric conditions. On the other hand, their absence is a sign that air conditions are not adequate.”

Vitorino and her colleagues focused their research in a permanent preservation area (PPA) in the municipality of Caiapônia, 335 kilometers (208 miles) from the Goiás state capital, Goiânia. The PPA is located within a private large-scale sugarcane concession.

The researchers collected lichens of the Parmotrema tinctorum and Usnea barbata species, the latter known as “old man’s beard,” from tree trunks in the center of the PPA, where, in theory, they wouldn’t have been directly exposed to glyphosate spraying in the concession. But their analyses found a decrease in living cells and increase in dead cells of the lichens. Both trends were proportional to the time of exposure to the herbicide and its concentration.

Vitorino said their interest in conducting this in-depth study arose after the detection of cadmium, one of the heavy metals present in glyphosate, in lichens located on the edges of four PPAs in Rio Verde municipality, Goiás. That survey, conducted in 2017, involved conservation areas located on private properties that grow commodity crops.

In 2018, the researchers’ concern increased with the discovery of glyphosate-linked heavy metals in lichens in Emas National Park, also in Goiás. Since the park is a fully protected conservation unit, where no commercial activity is permitted, there shouldn’t have been any glyphosate residue found in these living organisms.

It was then that researchers suspected contamination caused by drift — when groundwater and air currents carry pesticides beyond the areas where they were sprayed. Aerial spraying, the most common method in Goiás, is particularly conducive to the dispersion of glyphosate.

“These previous studies proved that there was contamination of lichens in conservation areas. The current study was more effective to show how lichens were affected,” Vitorino said.

The researchers chose to focus on the municipality of Caiapônia because it’s a relatively well-preserved area. Ideally, Vitorino said, they wanted to obtain lichens that had never had contact with glyphosate, in order to closely observe their reaction to stimuli during in-vitro analyses.

Biomarkers of glyphosate pollution in lichen samples. Image courtesy of dos Santos et al. (2023).

The research also found that glyphosate compromises lichens’ photosynthesis process, which is essential for survival. That’s how they convert sunlight into chemical energy, giving them food and oxygen.

In a fluorescence test, pictured above, exposing the lichens to a specific light shows the health of the algae that make up the organisms – the part responsible for photosynthesis. The algae virtually disappear in the last row. “This shows that glyphosate compromises the photosynthesis capacity of lichens,” Vitorino said.

The lichens’ response to glyphosate makes them stand out amid other bioindicators — species that can serve as an early warning of some kind of contamination in an ecosystem. “With this study, we do not mean to say that other species are not being affected [by glyphosate], but lichens have a faster response, something that may take time to appear in other species,” Vitorino said. She added the study confirms the dispersion of glyphosate to conservation areas, with aerial spraying playing a decisive factor.

Glyphosate, best known under the trade name Roundup, is the best-selling herbicide in Brazil, with nearly 220,000 metric tons traded per year, according to IBAMA, the federal environmental agency. The state of Goiás, where the lichen samples were collected, accounted for almost 20,000 metric tons of annual sales, also according to IBAMA. Glyphosate is also the top-selling pesticide worldwide.

A crested seriema (Cariama cristata) at Emas National Park, southwestern Goiás state. Image by Fernando Nanzer via Wikimedia Commons (CC BY-SA 4.0).

Cerrado: 70% of pesticides used in Brazil

According to medical doctor and public health expert Wanderlei Pignati, the arrival of transgenic or genetically modified seeds was decisive for the surge in the use of glyphosate and other pesticides in the Cerrado. “A type of soy resistant to glyphosate — Roundup Ready — was created, meaning glyphosate can be applied directly [to the plant]. It kills the weeds but not the soy,” he said. Other species have also been genetically modified for resistance to several types of pesticides.

The Cerrado accounts for 73.5% of the entire volume of pesticides sold throughout Brazil. This high consumption is due to the fact that the biome has thousands of hectares of commodity monocultures, making it the breadbasket of Brazilian agribusiness, according to a study published by the Federal Rural University of Paraná (UFPR).

Lichen of the Parmotrema genus on a tree limb in Matas do Segredo State Park, Mato Grosso do Sul state. These organisms are formed by fungi and algae, which interact with each other, and serve as a good indicator of poor air quality. Image by Fábio Júnio Santos Fonseca via Wikimedia Commons (CC BY-SA 3.0).

Poor air quality isn’t the only consequence of excessive use of pesticides that should cause concern. Research indicates that glyphosate and substances in other herbicides are probably carcinogenic.

Mata Mato is a brand of herbicide sold in Brazil that contains glyphosate as well as chemicals like polyoxyethylene amine, nitroglyphosate and formaldehyde. “While glyphosate is probably carcinogenic, the other substances have been proven to be carcinogenic,” Pignati said.

In 2015, the World Health Organization’s International Agency for Research on Cancer (IARC) classified glyphosate as “probably carcinogenic.” A technical report released in 2019 by the Brazilian Public Health Association (ABRASCO) calls for a ban on glyphosate-based products because of its likely carcinogenic potential.

The report advocates the precautionary principle — “a basic criterion in the processes of assessing potential harm to human health and the environment, indicating that exposure must be avoided because of limited information and/or uncertainties regarding the dangers of exposure to certain agents,” the note says.

Pignati noted that Resolution 441 of Brazil’s National Health Regulatory Agency (Anvisa) defines the prescribed safe limits for these substances. Polyoxyethylene amine may not exceed 20% by content in glyphosate-based products; nitroglyphosate, 0.001 grams per kilogram of glyphosate; and formaldehyde, 1 g/kg of glyphosate. “Are these limits respected when manufacturing the product? It’s important for us to know,” Pignati said.

Last-minute lifeline for glyphosate

In the European Union, the permit for producing glyphosate-based herbicides was set to expire in December 2023. On Oct. 13, the European Commission sought to extend it until 2033, but the decision didn’t get the necessary votes from member countries needed to approve it. As a result, the proposal to renew or reject went before the EC’s Appeal Committee, which also failed to deliver a decisive vote. In the end, the decision went back to the EC, which said it would “now proceed with the renewal of the approval of glyphosate for a period of 10 years, subject to certain new conditions and restrictions.”

Among EU member countries, Germany — home to agrichemical giant Bayer, which in 2018 acquired Roundup maker Monsanto — abstained on the vote, along with agricultural powerhouses France, Italy and the Netherlands. Others like Denmark, Spain and Portugal voted in favor of renewal, while Austria, Croatia and Luxembourg voted to reject it.

The split highlights the gulf between business groups fearful of a massive loss of revenue, including in Brazil, one of the largest glyphosate users in the world, and, on the other hand, research institutions, doctors and environmentalists who consider the evidence of the product’s carcinogenic potential to be more than enough to ban its use. With a ban on glyphosate, Brazilian agricultural producers seeking access to the EU market would have had to find more environmentally sustainable ways to farm.

Banner image: Aerial spraying in the municipality of Santo Inácio, Paraná state. Image by Edmarjr via Wikimedia Commons (CC BY-SA 3.0).

This story was reported by Mongabay’s Brazil team and first published here on our Brazil site on Oct. 30, 2023.


Santos, A. M., Bessa, L. A., Augusto, D. S., Vasconcelos Filho, S. C., Batista, P. F., & Vitorino, L. C. (2023). Biomarkers of pollution by glyphosate in the lichens, Parmotrema tinctorium and Usnea barbata. Brazilian Journal of Biology, 83. doi:10.1590/1519-6984.273069

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