AGRICULTURE
Solar radiation, temperature, and precipitation are the main drivers of crop growth; therefore agriculture has always been highly dependent on climate patterns and variations. Since the industrial revolution, humans have been changing the global climate by emitting high amounts of greenhouse gases into the atmosphere, resulting in higher global temperatures, affecting hydrological regimes and increasing climatic variability. Global warming is projected to have significant impacts on conditions food supply (how much food is produced) and food security.
Overall, climate change could result in a variety of impacts on agriculture. Some of these effects are biophysical, some are ecological, and some are economic including:
- A shift in climate and agricultural zones towards the poles
- Changes in production patterns due to higher temperatures
- A boost in agricultural productivity due to increased carbon dioxide in the atmosphere
- Changing precipitation patterns
- Increased vulnerability of the landless and the poor
However, agriculture is itself responsible for an estimated one third of global warming and climate change. It is generally agreed that about 25% of the main greenhouse gas, carbon dioxide, is produced by agricultural sources, mainly deforestation and the burning of biomass. Most of the methane in the atmosphere comes from domestic ruminants, forest fires, wetland rice cultivation and waste products, while conventional tillage and fertilizer use account for 70% of the nitrous oxides. According to the Intergovernmental Panel on Climate Change, the three main causes of the increase in greenhouse gases observed over the past 250 years have been fossil fuels, land use, and agriculture.
Over the past centuries, human ingenuity has led to technological advances in agriculture that have allowed substantial increase in crop yields, in part stimulated to meet population growth. Intensive agricultural methods are reported to have detrimental effects on the environment.
The agricultural sector has become one of the main driving forces in gas emissions and land use effects. For example, agriculture contributes to greenhouse gas increases through land use in different ways:
- CO2 releases linked to deforestation in temperate regions: where forests and woodlands are cleared to make room for fields and pastures.
- Methane releases from rice cultivation and enteric fermentation in cattle
- Nitrous oxide releases from fertilizer applications
Together, these agricultural processes comprise 54% of methane emissions, roughly 80% of nitrous oxide emissions, and virtually all carbon dioxide emissions tied to land use. Deforestation for land cleaning purposes also affects regional carbon reuptake, which can result in increased concentrations of CO2, the dominant greenhouse gas. Worldwide, livestock production occupies 70% of all land used for agriculture, or 30% of the land surface of the Earth.
