Trade-offs in water and carbon ecosystem services with land-use changes in grasslands

Increasing pressures for food, fiber, and fuel continue to drive global land-use changes. Efforts to optimize ecosystem services under alternative land uses are often hampered by the complex interactions and trade-offs among them. We examined the effects of land-use changes on ecosystem carbon storage and groundwater recharge in grasslands of Argentina and the United States to (1) understand the relationships between both services, (2) predict their responses to vegetation shifts across environmental gradients, and (3) explore how market or policy incentives for ecosystem services could affect land-use changes. A trade-off of ecosystem services was evident in most cases, with woody encroachment increasing carbon storage (+29 Mg C/ha) but decreasing groundwater recharge (-7.3 mm/yr) and conversions to rain-fed cultivation driving opposite changes (-32 Mg C/ha vs. +13 mm/yr). In contrast, crops irrigated with ground water tended to reduce both services compared to the natural grasslands they replaced. Combining economic values of the agricultural products together with the services, we highlight potentials for relatively modest financial incentives for ecosystem services to abate land-use changes and for incentives for carbon to drive land-use decisions over those of water. Our findings also identify key opportunities and caveats for some win-win and lose-lose land-use changes for more integrative and sustainable strategies for land management.