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Corn growers in Brazil’s Cerrado reap a hostile climate of their own making

  • Agribusiness entities that deforested vast swaths of the Cerrado biome in Brazil to grow corn are now suffering a drop in production because of climate changes brought about by their own actions.
  • That’s the finding of a new study that shows the loss of native vegetation has led to more warm nights and changes in rainfall patterns, affecting corn crops that require moderate temperatures and reliable rainfall.
  • The study’s authors say everyone loses from this scenario, and call for keeping the native vegetation in place as much as possible.
  • International pressure and a serious commitment from agribusiness, which is largely resistant to efforts to preserve the Cerrado, might be the way to stop deforestation, they suggest.

The vast Cerrado grasslands of Brazil continue to be cleared to plant corn and soybeans and to raise cattle. But the destruction has been so extensive that it has sparked a change in the local climate, making the region increasingly unsuited for corn farming.

That’s the finding from a new study by researchers from Dartmouth College looking into one of the many impacts that deforestation is having on the Cerrado. The key takeaway: the loss of native vegetation — more than half the Cerrado has been cleared — has caused an increase in the biome’s temperature and a decrease in rainfall, leading to a decline of up to 8% in yields of corn, one of the main commodities grown in the region.

Brazil is the world’s third-largest producer of corn, a crop that depends almost entirely on rainfall patterns and moderate temperatures for its development, since only 6% of the country’s land is irrigated. That’s given rise to the paradox that the same agribusiness entities responsible for deforestation in the Cerrado are the very ones now suffering a loss of production thanks to the environmental impacts they have brought about.

In the study, published in the journal Nature Sustainability, the researchers analyzed different land use scenarios in the Brazilian Cerrado and Amazon, using climate patterns observed from 2000 to 2015. In all the scenarios, the results pointed to a grim future for corn growers.

Four of the six scenarios focused on the Cerrado: before deforestation; deforestation in 2016; Cerrado vegetation replaced with exclusive soybean crops; and Cerrado vegetation replaced with a combination of soybean and corn. The other two scenarios considered soybean replacing rainforest in the eastern Amazon region known as the Arc of Deforestation; and a combination of soybean and corn in the same region.

An official from IBAMA, the Brazilian environmental enforcement agency, inspects a cornfield using a drone during Operation Shoyo Matopiba in April 2018. IBAMA and the Federal Public Ministry imposed about $20 million in fines for illegal cropping in off-limits areas of Cerrado following the operation. Image by Vinicius Mendonça/IBAMA.

All the post-deforestation scenarios showed an increase in the number of nights per year above 24° Celsius (75° Fahrenheit), defined as “warm nights” and considered the threshold above which corn crops can experience damage. Depending on the scenario, the study identified eight to 30 more warm nights per year compared with the period before deforestation, translating into a drop in corn production of between 6 and 8%.

Land clearing in the Cerrado is also shown to affect rainfall patterns. With less vegetation, there’s less evapotranspiration — the recycling of water back into the atmosphere from plants. As a result, the balance of water is seriously affected, especially during important periods of crop development. Compared to soybean, corn is much less resistant to heat and more dependent on rainfall, making for a bleak outlook for growers.

But beyond the growers, everyone loses, says Stephanie Spera, one of the study’s authors. The impact of deforestation affects the very reason for clearing the Cerrado in the first place, which is the production of crops. “Nothing could be more helpful than stopping deforestation and preserving what’s left of the Cerrado,” she says.

She notes the Cerrado is often referred to as an “inverted forest” in terms of carbon storage. While forests such as the Amazon lock much of their carbon stock in above-ground vegetation — tree trunks, branches and leaf litter — two-thirds of the estimated 13.7 billion tons of CO2 stored in the Cerrado are hidden beneath the soil, in the form of deep roots capable of absorbing water accumulated underground. This allows the vegetation to continue to evapotranspire even in the dry season, which in turn helps kick-start the rainy season.

“It is important to keep as much native vegetation intact so that the system remains as stable as possible in terms of carbon, water balance and energy balance,” Spera says.

Another effective and intelligent solution for growers, the study indicates, is to improve productivity in previously deforested areas and plant a cover crop during the dry season.

Changes in land use between 2000 and 2019 in a stretch of Cerrado in southern Piauí state. The clear areas are farmland. Image courtesy of Stephanie Spera et al.

Initiatives that have emerged in recent years with these goals, however, have not received the necessary support to succeed. The Cerrado Manifesto, for example, launched in 2017, asks companies that buy soybeans and meat from the Cerrado, as well as investors operating in these sectors, to make commitments to eliminate deforestation and dissociate their production chains from recently deforested areas.

Although it has obtained the formal support of more than 60 organizations, the manifesto has been met with great resistance from the companies responsible for the bulk of the commodities produced in the Cerrado, such as Bunge, Cargill, Amaggi and ADM.

Only 3% of the entire Cerrado is located in fully protected areas, and the Forest Code takes a lenient stance on devastation in the biome, requiring concession holders to preserve just 35% of their total area; in the Amazon, they would be required to preserve 80%.

A moratorium on soybean cultivation in the Cerrado, similar to the one applied in the Amazon, could prevent the direct conversion of 3.6 million hectares (8.9 million acres) of native vegetation into farmland in the next 30 years — an area bigger than Belgium.

“There needs to be a large financial incentive, with the entire European Union refusing to buy soybeans from Brazil, for example, for the big traders to feel any pressure to change,” Spera says.

Citation:

Spera, S. A., Winter, J. M., & Partridge, T. F. (2020). Brazilian maize yields negatively affected by climate after land clearing. Nature Sustainability. doi:10.1038/s41893-020-0560-3

Banner image of a corn plantation in Paraná, by Cleberson Beje/Faep.