Agricultural activities encompass the various processes we use to grow crops and raise livestock for food for human populations. Crops are also used for industrial processes, for example, palm oil is used in many products from frying oil to cosmetics, sugar cane waste is used for biofuel, and cotton is used for textiles. Livestock are used for meat, eggs, milk, as well as for leather and wool. Livestock are also used for labor.
Humans have altered Earth’s land for thousands of years through agricultural activities. Industrialization of many agricultural activities over the last 300 years, and especially over the last 70 years, has allowed us to greatly expand our land use. This has also fragmented habitats and ecosystems, affecting species populations and ranges and biodiversity.
Agricultural activities impact the Earth system in a variety of ways, including:
- Increasing greenhouse gases into the atmosphere, for example, from farm animals (for example, methane from the digestion of plant material by cows), from the cultivation of rice (for example, methane is produced by bacteria that thrive in rice fields), and from the burning of fossil fuels to power farming equipment, and from the mining of minerals and the burning of fossil fuels to make fertilizer.
- Deforestation and other forms of habitat loss to make land available for crops and grazing livestock. Habitat loss often alters populations, species ranges, and the biodiversity in ecosystems. Fire is often used in deforestation, which releases greenhouse gases into the atmosphere. Deforestation can also decrease soil quality by increasing erosion, necessitating the use of fertilizers that can also disrupt ecosystem biomass and productivity.
- Diverting freshwater for crops and livestock, which in turn decreases the amount of water available for other organisms and for other human needs and activities.
- Increasing food availability. Industrial and technological innovations increased the reliability of food supplies, especially the last 70 years, which in turn has played a role in global human population
- Increasing the amount of nutrients in soil or water, especially nitrogen and phosphorous. These nutrients increase plant and algae growth, but also have negative impacts on other species. For, example, in aquatic environments, nutrient-rich runoff can cause large amounts of algae grow – when the algae die, they are consumed by bacteria which can reduce oxygen levels in the water, killing fish and other species. This process is known as eutrophication.
- Releasing pollutants and waste from fertilizers and pesticides into ecosystems that can harm the health of native species populations. Pollutants and waste also decrease the quality of freshwater
- Removing trees and plants, plowing fields, and overgrazing by livestock disrupts roots that stabilize sediment and decrease soil quality. These human activities can increase erosion rates 10 to 100 times. In turn, increasing erosion decreases water quality by increasing sediment and pollutants in rivers and streams.
Can you think of additional cause and effect relationships between agricultural activities and other parts of the Earth system?
Visit the food quality & availability, population growth, greenhouse effect, and freshwater use, pages to learn more about how processes and phenomena related to agricultural activities affect global climate and ecosystems.