Between 1880 and 1980, the average global temperature rose from 13.73°C to 14.3°C – an average increase of 0.07°C per decade. Over the next 40 years, temperatures rose to an average 14.82°C – an increase of 0.18°C per decade. This recent acceleration in the rate of global warming is a direct result of anthropogenic greenhouse gas emissions.
The agricultural sector is responsible for an estimated 10% of the UK’s total greenhouse gas emissions, sitting in fifth place after the residential (15%), business (17%), energy supply (24%), and transport (27%) sectors. Around 85% of UK farmland is used for grazing livestock or producing crops to feed livestock, and almost 80% of the greenhouse gases produced by the farming industry can be attributed to animal rearing.
Agricultural emissions consist of 50% methane (CH4), 40% nitrous oxide (N2O), and 10% carbon dioxide (CO2). Let’s have a brief look at these greenhouse gases and their impact on the environment.
The concentration of atmospheric carbon dioxide, a natural product of respiration, has increased by more than 40% since the beginning of the Industrial Revolution – partly due to the burning of fossil fuel for energy production. Another contributing factor is deforestation. Carbon dioxide is absorbed by plants for photosynthesis, but with the destruction of large areas of forest, un-sequestered carbon dioxide remains in the atmosphere for as long as 1,000 years.
Around 40% of the world’s nitrous oxide emissions are due to human activity, and the atmospheric concentration of this gas is increasing at a rate of approximately 1 part per billion every year. Molecule for molecule, the global warming potential (GWP) of N2O is more than 250 times that of carbon dioxide.
An important component of amino acids and nucleic acids, nitrogen is important for the growth and development of plant proteins and DNA.
Nitrogen accounts for approximately 78% of the Earth’s atmosphere. The gas occurs as a triple-bonded molecule (N2) that’s inaccessible to plants because they’re unable to break the strong triple bond that holds the two nitrogen atoms together. The process of breaking apart a nitrogen molecule (“nitrogen fixation”) is performed by microorganisms in the soil, and the by-product is nitrous oxide.
The agricultural sector uses nitrogen-rich fertilizers, which add more nitrogen to the soil than is required by crops. Farming produces around 75% of the UK’s N2O emissions, and, globally, livestock is responsible for 65% of all anthropogenic N2O emissions.
More than 40% of anthropogenic methane emissions are produced by agriculture.
Methane, which doesn’t have the longevity of carbon dioxide but holds a lot more energy, has a net GWP of between 28 and 36 over a period of 100 years.
Methane is a by-product of enteric fermentation, the organic decomposition by microorganisms (methanogens) in the digestive systems of ruminants. In the last 50 years, the world’s human population has doubled, and so has milk production. Meat production has tripled. As of 2021, there are 1,400,000,000 domesticated cattle and 1,000,000,000 domesticated sheep on Earth, all emitting methane gas.
Since the beginning of the Industrial Revolution, the concentration of atmospheric methane has more than doubled.
Approximately 5,000,000,000 hectares (38%) of the world’s land surface is used for agriculture. Two thirds of this land is grazing pasture for livestock, and the rest is cropland – of which roughly one third is used to grow feed for livestock.
Around 10,000,000 hectares of forest area are lost every year to alternative land uses, and hundreds of tree species are now considered critically endangered. Reduced foliage means reduced CO2 absorption, and so atmospheric carbon dioxide levels are increasing.
The negative effects of deforestation, however, are not limited to global warming. Loss of biodiversity is another huge threat to the world’s ecosystems and to human civilization.
In a 2017 study, scientists documented the population sizes and geographical ranges of 27,600 vertebrates – including detailed observation of 177 mammal species – between 1900 and 2015. The purpose of the study was to demonstrate the extent of “anthropogenic erosion of biodiversity”.
It was revealed that approximately 32% of the species included in the study had decreased in population size and geographic range. All 177 mammals that were closely documented had lost at least one quarter of their geographic ranges, and 40% of those species had experienced severe population decline.
Each year, on 1 November, vegans all over the world celebrate and champion their contribution to a healthy planet.
The overriding message on World Vegan Day is that a vegan diet is the single biggest way to produce your carbon footprint.