Assessing the restoration of grassland plant communities and bird habitat in the Conservation Reserve Program.

Abstract

The United States Department of Agriculture administers the Conservation Reserve Program (CRP) to stabilize crop prices and incentivize soil, water, and wildlife conservation. The program awards 10-15 year contracts for landowners to restore perennial vegetation on marginal cropland in exchange for annual rental payments. With a 22-million acre footprint, CRP is the single largest private lands habitat restoration project in the nation. CRP is particularly important for biodiversity conservation and restoration in the Tallgrass Prairie Region (TGPR). Tallgrass prairie is among the most endangered ecosystems in the world, and the grassland birds that depend on this habitat have been precipitously declining for a half century. These conservation challenges warrant evaluation of the biodiversity outcomes of CRP. In summer 2023, we measured plant community composition and bird abundance on 15 16-hectare grasslands in the Tallgrass Prairie Region in western Minnesota and the eastern Dakotas: five low-diversity CRP practices, five high-diversity CRP practices, and five remnant prairies. The diversity category assignment for a site corresponded to the relative species diversity of the seed mix planted on the site. We observed a general trend towards higher plant community quality (higher mean coefficient of conservatism and lower proportion of non-native plants) from low-diversity CRP to high-diversity CRP to remnant prairies, but only observed a diversity trend in the higher alpha diversity found in remnant prairies compared to all CRP plantings. However, we did find a positive, significant relationship between frequency of disturbance and plant alpha diversity. At the same time, the abundance of 10 grassland bird species was positively associated with plant community alpha diversity, beta diversity, and mean coefficient of conservatism. Based on these results, we recommend that CRP amplifies efforts to restore diverse grasslands in the TGPR to recreate habitat with the potential to support more dense populations of grassland birds. This can be accomplished through using more diverse seed mixes and encouraging disturbance regimes that more closely resemble those found on historic tallgrass prairies. An additional 18 sites sampled in summer 2024 will help to solidify causality and significance in the relationships identified in these preliminary analyses.