Pressure indicators

Fossil fuel consumption

The combustion of fossil fuels releases various pollutants, including CO₂ (Houghton et al., 2000; IPCC, 2007). CO₂ emissions from the consumption of fossil fuels account for most of the increase in atmospheric CO₂ levels (Houghton et al., 2000; IPCC, 2007; Environment Canada, 2008). However, this gas is also emitted as a result of logging, biomass burning and other non-energy processes such as cement production (Houghton et al., 2000; WRI, 2005; IPCC 2007). CO₂ is considered the most important greenhouse gas (GHG) as it is highly persistent in the atmosphere (between 5 and 200 years) and is the gas emitted in larger amounts (IPCC, 2007). Similar to other countries, most CO₂ emissions in Mexico are associated with fuel combustion (Semarnat-INE, 2009). The indicator Global CO₂ emissions from fossil fuel consumption reflects the extent of global pressure exerted in the same way as the National CO₂ emissions from fossil fuel consumption indicator shows this pressure at the country level. These indicators are used in various international initiatives promoted by the OECD, Environment Canada and the US-EPA, among others (OECD, 2005; Environment Canada, 2008; EPA, 2009).

Land-use change and forestry

About 18% of global GHG emissions result from land use change, with deforestation being the major process involved (WRI, 2005). Terrestrial vegetation and oceans jointly capture about one half of total CO₂ emissions (IPCC, 2007). Clearance of the plant cover alters the carbon-flux balance (Houghton, 2000; WRI, 2000; IPCC 2007), since the amount of CO₂ fixed by plants drops, on the one hand, and CO₂ is released through organic matter breakdown, on the other (Semarnat-INE, 2006). In contrast, reforestation promotes carbon sequestration (Semarnat-INE, 2006; IPCC 2007). A study published by the United Kingdom Royal Society highlights the importance of the removal of vegetation cover in carbon flux, and estimated that deforestation in the Amazon produces between 5 and 10% of global CO₂ emissions (Royal Society, 2007). In Mexico, although a historical data series is not available, an estimate of the National CO₂ emissions and sequestration from land-use, land-use change and forestry for the period 1993-2002 shows the pressure imposed by one of the major sources of CO₂ emissions.