Pressures: emissions

5.2.6 Agricultural and forestry

A broad array of agricultural and livestock farming practices alter the nitrogen cycle and GHG emissions, and increase pollution by fertilizers and pesticides, promoting biodiversity loss and soil degradation (DeLonge, Miles and Carlisle 2016). Agriculture, forestry and other land uses contribute 25 per cent to global GHG emissions (Seto et al. 2014). In developed countries, agriculture forms about 10 per cent of national GHG inventories (European Environment Agency 2017; US EPA 2017), while in developing countries the contribution is much higher.

Meat and dairy production, distribution and consumption have large environmental impacts on scales ranging from local to global (Leip et al. 2015). Industrial meat production and livestock operations are significant sources of GHGs, NH3, dust and bioaerosols (Cole and McCoskey 2013). GHG emissions from livestock farming increased by 51 per cent globally between 1961 and 2010, mostly due to a 117 per cent increase in developing countries, moderated by a 23 per cent decrease in the developed countries (Caro et al. 2014; Pagano et al. 2017). Livestock production is responsible for 9 per cent of total GHG emissions (Caro et al. 2014). The largest source of these emissions (74 per cent) are dairy and beef cattle. N2O and CH4 emissions, which emanate from manure left on pasture, manure management and fermentation, increased by 57 per cent globally in the same period. However, rotational livestock grazing and other pasture management techniques are available to decrease the production of GHGs by the very same cattle, and at the same time preserve biodiversity (Nordborg and Röös 2016).

Along with livestock farming, fertilizer use results in significant emissions of NH3, accounting for about 75 per cent of anthropogenic and about 60 per cent of total NH3 emissions globally (Ciais et al. 2013) and contributing to regional PM formation and detrimental effects on terrestrial, freshwater and marine ecosystems (Galloway et al. 2003).

Irrigation and fertilization practices for crops in general, as well as pasture management, can alter soil respiration rates, changing the amount of CO2 emitted by soils to the atmosphere (UNEP 2017c). Pesticides used in agricultural applications are a major source of unregulated POPs into the environment and food chain, with various detrimental effects on health (see Section 4.3.4).

Biomass burning – including natural wildfires, prescribed burning of crop and forest residues, and prescribed burning of forests and savannah for land clearing – contributes significantly to air pollution by emitting CO, OC, BC, NOX and NH3, as well as GHGs, CO2 and CH4. Dominant types of biomass burned are savannah in Africa; boreal forest in the former Soviet Union, savannah and tropical forest in Latin America; and savannah, peat and tropical forest in eastern Asia. Biomass burning in South-East Asia, the drought triggered by the 2015-2016 El-Niño, coupled with anthropogenically induced deforestation over peat swamps and effects of previous widespread fires, have all led to severe regional air pollution events (Wooster, Perry and Zoumas 2012; Koplitz et al. 2016; Parker et al. 2016) (see Section 12.2.5).