The study by Suding et al. examines the mechanisms behind the decline in plant species diversity due to increased nitrogen (N) availability in terrestrial ecosystems. Based on a meta-analysis of 34 N-fertilization experiments across nine ecosystems in North America, the authors find that both trait-neutral and trait-based mechanisms contribute to diversity loss as production increases. Rare species are particularly vulnerable to loss due to soil fertilization, with the risk ranging from over 60% for the rarest species to 10% for the most abundant species. Perennial species, those with N-fixing symbionts, and native species also face increased risk of local extinction after fertilization, regardless of their initial abundance. Abundance consistently plays a significant role across all systems, while functional mechanisms are often system-dependent. The findings suggest that managing for locally susceptible functional groups and generally rare species will be crucial to maintain biodiversity as N availability continues to increase globally.The study by Suding et al. examines the mechanisms behind the decline in plant species diversity due to increased nitrogen (N) availability in terrestrial ecosystems. Based on a meta-analysis of 34 N-fertilization experiments across nine ecosystems in North America, the authors find that both trait-neutral and trait-based mechanisms contribute to diversity loss as production increases. Rare species are particularly vulnerable to loss due to soil fertilization, with the risk ranging from over 60% for the rarest species to 10% for the most abundant species. Perennial species, those with N-fixing symbionts, and native species also face increased risk of local extinction after fertilization, regardless of their initial abundance. Abundance consistently plays a significant role across all systems, while functional mechanisms are often system-dependent. The findings suggest that managing for locally susceptible functional groups and generally rare species will be crucial to maintain biodiversity as N availability continues to increase globally.