Two research groups – one from São Paulo and another from Rio Grande do Sul – have identified almost 2,000 craters in the seabed of parts of Brazil’s south-eastern and southern coast, around 200 kilometers from the mainland. Approximately 230 meters wide and 90 meters deep, these deepsea holes, known as pockmarks, are formed by the eruption of gases from the seabed, mainly methane (CH4), one of the causes of the greenhouse effect. However, it is estimated that most of the methane is consumed by bacterias and other organisms in the ocean, before making it to the atmosphere.
There is yet to be any data about the contribution of seabed craters off the Brazilian coast to the country’s total emission of greenhouse gases, which in 2014 stood at 2 billion tons, the equivalent of around 5 percent of the world’s total, in accordance with the Ministry of Science, Technology, Innovation, and Communications. Produced mainly by farming and the treatment of waste, methane contributes to 24 percent of total emissions (the volume of gas which remains in the atmosphere after subtracting the total emissions of carbon taken from human activity, such as the restoration of forests).
Carbon dioxide (CO2), mainly caused by the combustion of fossil fuels, accounts for 64 percent of total emissions; nitrous oxide (N2O), from the fertilization of soil, makes up 12 percent. Methane lasts much less time in the atmosphere than CO2, but its capacity to retain heat is 21 times higher, while N2O is 310 times higher than CO2.