CC Cerri

Carlos Clemente Cerri is a Brazilian agronomist. He is full professor at the Center for Nuclear Energy in Agriculture (CENA) of the University of São Paulo (USP), Brazil, where he teaches graduate courses on agriculture and climate change and conducts research on: the effects on global warming of agricultural land use in the tropics; greenhouse gases affecting climate change (temperature) emitted from soil organic matter and the decomposition of plant residues; the mitigation of greenhouse gas emissions from agriculture and husbandry; and the carbon footprint of ethanol from sugarcane and biodiesel from oil crops, examining innovative technologies to enhance offsets of fossil fuels.

Cerri earned his master’s degree and PhD in Soil Science and Environment in 1974 and 1979, respectively. He has published more than 150 scientific papers in prestigious international journals, written over 30 book chapters and edited 5 books. He has also advised more than 40 master’s and PhD students from Brazil and abroad.

His initial research focused on soil organic matter dynamics, particularly in humus characterization, under different natural ecosystems and agricultural land uses in Brazil. Recently, he carried out an estimation of total organic carbon in the soils of Brazil.

In the early 1980s, Cerri built equipment to follow and quantify the carbon flux in the soil-plant-atmosphere system, using ¹⁴C-CO₂ as a tracer. With this equipment, he was able to analyse the plant stresses due to increasing CO₂ concentrations and temperatures under low soil water-holding capacity.

In 1985, he developed a method using the ratio ¹³C/¹²C of stable isotopes to distinguish the origin of soil carbon. This method allows researchers to quantify how much CO₂ from the atmosphere has been introduced into agricultural soil via plant residues and how much is emitted to the atmosphere.

Cerri pioneered estimates of soil microbial biomass activity under native and cultivated soils in Latin America. Humus characterization, isotopic methodology, as well as soil microbial biomass estimation, were not only shared with other Brazilian institutes but also with colleagues in other countries of South America and the Caribbean.

In the early 1990s, his research focused on the environmental impact of Amazonian deforestation, with an emphasis on greenhouse gas emissions (CO₂, CH₄, N₂O). He calculated the gain and loss of carbon in the soil-plant-atmosphere system using 11 soil chronosequences composed of forest and pastures of different ages in the Brazilian Amazon basin, which allowed the quantification of the above-ground biomass of different types of Amazonian tropical forests and the rate of CO₂ emission due to slash-and-burn clearing. One of Cerri’s present research areas focuses on the impacts that agricultural expansion has on greenhouse gas emissions in the region, in order to develop innovative agricultural technologies capable of mitigating global warming. He is the coordinator of a large research project taking place in the Brazilian Amazon. The study, which covers an area of 1.2 million km² in the two most heavily deforested states of Rondonia and Mato Grosso, integrates environmental techniques (soil property characterization, geographic information systems, remote sensing, geostatistics, modelling approaches) and associated human dimensions. More than 30 research workers and students from different parts of Brazil and other countries are participating in the project.

Comparing conventional agricultural practices with best management practices to mitigate global warming, Cerri is focusing on two issues in particular: (a) burning vs. non-burning sugarcane harvesting systems in the state of São Paulo, and (b) conventional tillage vs. minimum or no-tillage in soybean plantations in the southern and central parts of Brazil. In the southern region, under no-tillage systems the rate of soil carbon accumulation was estimated at 0.8 t C ha^-1 yr^-1 in the 0–20 cm layer. This value is greater than that found in the central area of the country (0.4 t C ha^-1 yr^-1). These accumulation values refer to identical periods after switching from conventional to no-tillage practices. On the basis of the limited data currently available, the adoption of this particular type of best management practice appears to be a good option to mitigate global warming in Brazil. However, other gases, especially N₂O emitted by fertilization, still need to be taken into account to assess the total gain.

Fossil fuel burning is the main cause of climate change. By producing biofuels, Brazilian agriculture could contribute to mitigating the effects of climate change. Biofuels, however, should be produced in an environmentally friendly way (low carbon emissions) to increase the fossil fuels offsets. Cerri’s research team is currently quantifying the agricultural carbon footprint of biodiesel from oil crops (soybean, palm oil and castor oil) and of ethanol from sugarcane. The team is also studying the feedback of climate change on agricultural soils. Incubation experiments in the laboratory and simulation models are used to quantify the emission of CO₂ and other greenhouse gases to the atmosphere.