Impacts of Land-use Change on Carbon Stocks and Dynamics in Central-southern South American Biomes: Cerrado, Atlantic Forest and Southern Grasslands - Soil Carbon: Science, Management and Policy for Multiple Benefits - page 243

21 Impacts of Land-use Change
on Carbon Stocks and Dynamics in
Central-southern South American Biomes:
Cerrado, Atlantic Forest and Southern
Grasslands
Heitor L.C. Coutinho*, Elke Noellemeyer, Fabiano de Carvalho Balieiro,
Gervasio Piñeiro, Elaine C.C. Fidalgo, Christopher Martius
and Cristiane Figueira da Silva
Abstract
Land-use changes (LUC) are one of most significant global change processes of the current era, with
noticeable consequences on habitat loss, due mainly to agricultural expansion and urbanization. The
carbon cycle dynamics can be affected significantly by LUC, with impacts on carbon sequestration and
emission rates. Considering the direct effect of carbon gases enrichment of the atmosphere on climate
change, it is of utmost importance to improve the knowledge base on the impacts of agricultural-based
LUC on carbon sinks, such as soils. This chapter reviews the available data on the effects of LUC on
soil carbon stocks in three major biomes of the southern portion of the South American continent (the
Cerrado, the Southern Grasslands and the Atlantic Forest). The area of soybean crops has expanded
almost four times in the La Plata Basin Grasslands of Argentina over the past decade, and near ten
times in the Brazilian Cerrado since the mid-1980s. The area under sugarcane crops in Brazil has al-
most doubled since the mid-1990s, occupying approximately 8.5 million ha (Mha) in 2009. In 2011,
forestry plantations occupied 28% more land in Brazil than in 2005, with a total area of 6.5 Mha (75%
with Eucalyptus and 25% with Pinus ). In general, all conversions of natural vegetation to agricultural
land-use systems in the different biomes have resulted in significant losses of soil carbon stocks. The con-
version of pastures and grasslands to annual croplands in the Rolling Pampas grasslands has decreased C
stocks by 50% over the last century. This represents a much faster loss rate than the loss triggered by the
introduction of domestic herbivores over the course of the previous nearly four centuries (22%). These
results imply that soil degradation caused by annual crops is very rapid and results in a strong de-
crease in carbon stocks. However, adopting soil and water conservation management strategies and
increasing the complexity of the cropping systems - through adoption of no-tillage (NT) agriculture,
well-managed pasture systems, integrated crop-livestock-forestry systems, multiple cropping and
crop rotation with legume cover species, for example, can improve soil carbon sequestration rates by
up to nearly 2.0 Mg C ha - 1 year - 1 . The elimination of preharvest burning practices in sugarcane crops
alone can result in gains of up to 0.93 t C year - 1 ha - 1 . Improving soil and crop management to boost
carbon sequestration in agricultural systems, while at the same time increasing resilience by improv-
ing soil quality, is a potential climate change mitigation option for farmers in South America.