The total effect on the environment of animal farming can be divided into…
The so-called ‘Livestock Revolution’ occurring in most of the developing countries has already caused serious environmental problems…
- direct impacts such as gas emissions, pollution, and soil degradation, and
- indirect impacts such as the production of grain and animal feed required for cattle nutrition;
- in the food production cycle, farming has the largest environmental impact, but manufacturing and household consumption also play key roles due to their high use of energy, water consumption and waste production.
- through the expansion of land for livestock development, livestock sector growth has been a prime force in deforestation in some countries such as Brazil: millions of hectares of tropical rainforest have been lost due to increased ranching and crop cultivation;
- in Central America, for instance, 6 million hectares have been converted to pasture since 1950, whereas more than 50% of the pasture areas in the Amazon region have been abandoned because they are now too degraded;
- in other countries, overgrazing may cause soil erosion, decrease in fertility and organic content, water infiltration and soil compaction. These effects are already observable in large regions of Africa where the time required for land recovery is not respected anymore, and animals are kept in high numbers on the same spot for long periods;
- the greatest pressures on the environment from intensive farming - mostly in the industrial countries but increasingly in the developing ones - are methane and ammonia (NH3)* emissions, water and soil pollution due to slurry and manure accumulation, eutrophication and pathogenic contamination;
- it has been estimated that the annual global emissions of atmospheric ammonia by domestic animals account for 23 million tonnes of NH3-N. Fifteen million tonnes come at present from all developing countries (including China). The projected value for NH3 emissions from animal excreta in the year 2025 is 8.4 million tonnes in East Asia alone (including China), compared with 4.0 million tonnes in 1991;
- the digestion of food by some animals has emerged as a major threat to the environment due to the large contribution to the greenhouse effect of its methane emissions.** It has been estimated, for instance, that livestock and manure management produce 550 million tonnes of methane annually.
* NH3 is a very important atmospheric pollutant with a variety of effects including a contribution to soil acidification, which can lead to eutrophication when animal slurry contaminates water. It must be pointed out that an additional load of nitrogen comes from the synthetic fertilizers which are used in the production of feed crops.
** Methane is a gas that is 25 times more dangerous than CO2, and which is produced naturally during the digestion of food by ruminants.