Modern agriculture, food production and distribution are major contributors of greenhouse gases: Agriculture is directly responsible for 14 per cent of total greenhouse gas emissions, and broader rural land use decisions have an even larger impact. Deforestation currently accounts for an additional 18 per cent of emissions.
In this context, a historical perspective needs to be considered: Dr. Rattan Lal, Professor of Soil Science at Ohio State University, has calculated that over the last 150 years, 476 billions of tonnes of carbon has been emitted from farmland soils due to inappropriate farming and grazing practices, compared with ‘only’ 270 Gt emitted from of burning of fossil fuels. A more frequently quoted figure is that 200 to 250 Gt of carbon have been lost from the biosphere as a whole in the last 300 years. Whatever the correct figure, these reductions of ‘living carbon potential’ have resulted from
- biodiversity loss
- accelerated soil erosion
- loss of soil organic matter
- salinisation of soils
- costal water pollution and
- acidification of the oceans
Land use changes can also significantly contribute to climate change. Large scale changes such as deforestation, soil erosion or machine-intensive farming methods may all contribute to increased carbon concentrations in the atmosphere. Soil erosion by water, wind and tillage affects both agriculture and the natural environment. Soil loss, and its associated impacts, is one of the most important (yet probably the least well-known) of today’s environmental problems.
The contribution of farm animals to global greenhouse gas emissions is quite significant: