Tropical Agriculture and Emissions of Green House Gases: the Case of Brazil

Abstract

The activity of atmospheric Greenhouse Gases (GHGs), such as Water Vapor (H2O), Carbonic Gas (CO2), Methane (CH4), Nitrogen Oxides (NxO), and Ozone (O3), became an object of study because of their concentration rise in the atmosphere, increasing air temperature, drought events, and other factors stresses. However, most studies of their effects on agriculture were done in a temperate climate, especially in the northern hemisphere, with only a few studies in the tropics. For example, there are only two seasons in a tropical environment, the dry and the rainy season. In the tropics, there is an increase in anthropogenic and natural fires and, consequently, GHGs formation during the winter (dry season) due to biomass burning, considered the principal source of GHGs in the tropical climate. The concentration of GHGs in the atmosphere, produced principally during the dry season, is still high at the beginning of the rainy season. In addition to CO2 produced by biomass burning, there was an increase in Volatile Organic Compounds (VOCs), and NxO formed naturally in the Amazonian forest or due to biomass burning. VOCs and NxO, in ambient with high Ultraviolet Radiation (UV), generate O3, toxic to all living beings. The beginning of the summer (rainy season) is the principal sowing season in Brazil, but the GHGs are still high, causing effects on crops. Therefore, the GHGs, CO2, CH4, VOCs, NxO, and O3, are produced in tropical countries, like Brazil, but from different sources than in temperate climates. In tropical agriculture, CO2 air concentration increases from biomass burning, Amazonian Forest respiration, agriculture, soil respiration (microorganisms and roots), fossil fuel burning, growing plants and microorganisms during the wet season, etc. CH4 concentration increases from the Amazonian forest (Wetlands), flooded land (Pantanal in the Cerrado biome), oceans, enteric fermentation (cattle and thermites), garbage dump, biomass burning, etc., O3 air concentration increases from biomass burning, Amazonian forest, lightning, etc., VOCs concentration increases from biomass burning, Amazonian forest (Produces more than 80% of Global Isoprene), etc. NxO air concentration increases from biomass burning, Amazonian Forest (Wetland), nitrogen fertilization, smaller than in developed countries, rapid organic matter decomposition due to microbial activity all year long in tropics, etc.