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. Climate change is projected to have significant impacts on agricultural conditions, food supply, 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:
However, agriculture is itself responsible for an estimated one third of climate change. It is generally agreed that about 25% of carbon dioxide emissions, are produced by agricultural sources, mainly deforestation, the use of fossil fuel-based fertilizers, 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:
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.
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