Restoring vegetation cover in Amazon's pasture areas can reduce methane emissions, study reveals

Recovering vegetation cover in pasture areas can reduce methane emissions and the impact of livestock on the climate, according to a new study by AMI member Leandro Fonseca de Souza, Assistant Professor at the Federal University of Espirito Santo, Brazil.

It is estimated that up to 80% of deforested areas in the Amazon are used as pasture. One of the most well-known environmental impacts of livestock farming is the emission of greenhouse gases that contribute to global warming, a phenomenon that raises the Earth’s average temperature.

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A recent study conducted by the Center for Nuclear Energy in Agriculture (CENA) at the University of São Paulo (USP) on the Amazon indicates that restoring degraded pastureland can reduce methane emissions. Methane is produced by the decomposition of organic matter and is one of the main greenhouse gases. The paper appears in Science of the Total Environment.

“We concluded that proper pasture management in the Amazon, aimed at maintaining soil vegetation cover, can reduce methane emissions from livestock farming,” says biologist and Ph.D. candidate at CENA-USP, Leandro Fonseca de Souza. He conducted the research by analyzing emissions and microorganisms in Amazonian soil.

Microbial methane cycle

The biologist explains that both methane-producing and methane-consuming microorganisms inhabit the soil. “In forest soils, there are more consumers, whereas in pasture soils, there are more producers. We observed that in well-maintained pastures, the roots of grasses reduce the number of methane-producing microorganisms, leading to higher methane consumption than production.”

According to Souza, existing estimates indicate that 60% to 80% of deforested areas in the Amazon are used as pasture, and 40% to 60% of them are degraded to some extent.

“Degraded pastures in the Amazon are problematic both for producers and the environment because they become unproductive lands and no longer provide ecosystem services that a forest does—such as natural environmental regulation, which is essential for human well-being,” he explains.

Pasture expansion

In August, the MapBiomas project, a partnership between universities, NGOs, and technology companies that monitor land use in Brazil, reported that for every 10 hectares deforested in the Amazon, one is used for agriculture, urbanization, or mining; three are abandoned; and six become pasture.

Monitoring also showed that pasture expansion has intensified in the Legal Amazon. In 2005, the region had 45 million hectares of pasture, which increased to 53 million hectares by 2018.

The search for new pasture areas encroaching on the Amazon rainforest may be linked to the region’s naturally acidic soil, which is not ideal for grazing.

Nutrient-poor soils

“Pastures in the Amazon region have nutrient-poor soils, as they originate from former forest soils, which are usually more acidic and contain high levels of aluminum,” explains Souza. He adds that these soils tend to degrade more easily when pastures are poorly maintained.

Another reason for the search for new areas to exploit is economic. “Recovering degraded soil is costly and requires time and resources,” says Souza.

Agricultural engineer and researcher at Embrapa, Moacyr Bernardino Dias Filho, also sees the recovery of degraded areas in the Amazon as the best solution.

“Livestock farming in the Amazon is essential for regional and national food security. However, this activity can no longer be conducted in an amateurish manner,” he states.

“In numerical terms, for every hectare of degraded pasture restored in the Amazon, about three hectares could be freed for other purposes—agriculture, forestry, or conservation—without reducing the region’s current levels of meat or milk production,” Dias Filho points out.

Brazil’s commitments

Brazil has the world’s largest commercial cattle herd, with approximately 209 million head of cattle, according to 2016 data from the Brazilian Association of Meat Exporting Industries (Abiec).

This position makes Brazil one of the largest contributors to greenhouse gas emissions, according to the Intergovernmental Panel on Climate Change (IPCC), mainly due to methane, a pollutant gas produced in landfills, garbage dumps, and pastures. Methane has 21 times the global warming potential of carbon dioxide, the gas used as a baseline for measuring emissions.

In 2015, during the UN Sustainable Development Summit, Brazil committed to reducing greenhouse gas emissions by 43% by 2030.

15 million hectares

Restoring pastures with degraded soils is one of Brazil’s targets in the Paris Agreement. To reduce emissions, the country pledged to recover over 15 million hectares of degraded pastureland by 2030.

“Well-managed pastures are very efficient at storing carbon and can even sequester more carbon in the soil than native forests,” explains Dias Filho.

Thus, tropical pastures are a highly effective land-use system for capturing atmospheric CO₂ and play an important role in mitigating greenhouse gas emissions.

Government support needed

However, according to Dias Filho, achieving this goal requires technical and economic incentives from the government in the Amazon region to transition livestock farming from an amateur to a professional activity.

“There must be government support for technology development in livestock farming through the strengthening of research institutions and higher education in the Amazon. Likewise, the government should prioritize attractive financing policies for less-capitalized producers to adopt these technologies, as well as strengthen public technical assistance for these producers,” he advocates.

Reprinted with kind permission of DW.