160 The role of grazing lands in climate change mitigation.

Abstract Agriculture has historically provided much more than just food. It offers a multitude of societal and environmental benefits, including water storage, climate regulation, wildlife habitat, and biodiversity. However, today’s agriculture faces increased pressure to meet global demand for food, while balancing economic and environmental goals. Livestock production, in particular, has been the subject of increasing scrutiny due to its significant environmental footprint. However, adoption of conservation practices can serve as a means of producing food with lower, or even net positive environmental impacts. Globally, many grazing land ecosystems are facing degradation due to improper management. This is particularly evident in the southeastern USA, where extensive areas of planted pastures are degraded due to inadequate nutrient and soil management. Adoption of management practices intended to increase soil carbon (C) sequestration such as fertilization, grazing management, irrigation, sowing legumes, prescribed fire, and species selection can also have co-benefits for forage and livestock production and, therefore, they may also provide an additional incentive for adoption. However, the impact of a specific grazing land management practice on soil C is site-specific, climate-dependent, and influenced by factors such as soil and vegetation type. Therefore, careful evaluation of the benefits and trade-offs is necessary before implementation. The current lack of quantitative understanding of the direction and extent of management-induced soil C responses in subtropical and tropical regions hinders adoption of C conservation practices. From a research perspective, lack of long-term studies to inform management strategies that can potentially increase soil C sequestration in the southeastern USA represents a major barrier. Although a much larger body of literature is available in temperate regions in the USA and other parts of the world, greater effort is needed to evaluate grazing land management effects on soil C stocks in the subtropical regions. In this presentation, we will discuss the opportunities and challenges associated with increasing soil and ecosystem C sequestration in subtropical grazing lands through conservation management practices. Increased opportunities currently exist for agriculture to play a vital role in climate change mitigation. However, for this to happen it will be important to improve the accuracy of estimates associated with the adoption of specific management practices on ecosystem C balance at multiple scales (from field, farm, and national level). Generating reliable metrics that can also be used as benchmarks for ecosystem services credit market may also provide a critical step in increasing adoption of conservation practices.