Agricultural practices contributing to aquatic dead zones

Abstract

Aquatic dead zones are areas of decreased biodiversity due to hypoxic conditions. Runoff from farms often contains high levels of nutrients, particularly nitrogen and phosphorus, which flows into larger bodies of water and eventually the ocean and stimulates algal growth. When the algae die, they settle to the bottom and are decomposed by bacteria. The amount of oxygen produced by photosynthesis is exceeded by the amount of oxygen consumed during decomposition, thus leading to hypoxia in the bottom waters. This low oxygen starves organisms such as fish and shellfish, leading to decreased biodiversity or extinction of animal life in the area. Dead zones are linked to agricultural activity and are growing, which poses a threat to both aquatic organisms and humans. In this chapter, the case of the Gulf of Mexico dead zone is elaborated and sustainable solutions are posed to help mitigate this growing problem. The US “baby boom”, a marked population increase, directly impacted the farming industry, and larger industrial farms have since been used to supply the buyers’ needs. These farms use practices that are not sustainable including planting monoculture crops that have poor nutrient absorption, planting crops that alter the soil composition causing increase flooding, and using chemical fertilizers. By identifying the source of the nutrients that cause dead zones, more sustainable solutions have been identified to stop the growing areas of hypoxia. Larger industrial farms are directly influencing the size and continual growth of the dead zones. Sustainable farming practices benefit both the consumers and aquatic ecosystems, and this chapter gives practical solutions for sustainable agriculture.