Grassland destruction causes shifts in plant traits that persist during recovery.

Old-growth grasslands assemble over millennia and support high biodiversity and many ecosystem services, but continue to undergo widespread destruction for production of crops, timber, and minerals. How biodiversity recovers after grassland destruction and the functional consequences of this recovery can be informed by plant functional traits-i.e., morpho-physiological features that influence growth, survival, and reproduction. Yet we lack understanding of how functional traits differ between old-growth and secondary (i.e., recovering) grassland plant species at the global scale, hindering understanding of community assembly processes that transcend geographical regions. Addressing this gap, we synthesized trait data for 742 plant species from 24 studies across six continents to understand how plant species indicative of old-growth and secondary grasslands compare in their traits. Compared to old-growth grasslands, plants indicative of secondary grasslands were taller and had leaves with more nitrogen content, higher specific leaf area, and lower dry-matter content. Notably, these trait differences that make old-growth grassland plants more resource conservative and secondary grassland plants more resource acquisitive persisted over a century. Taken together, these findings help to explain why many secondary grasslands support altered plant communities for decades to centuries and emphasize the importance of old-growth grassland conservation in the light of the unique plant forms and functions they support. Persistent trait shifts associated with grassland destruction could accelerate nutrient cycling, and our findings provide guidance for recovering old-growth grassland biodiversity through ecological restoration.