Accumulating time lags across biodiversity levels following land‐use change

Abstract Delayed biodiversity responses to environmental changes occur from genes over communities to ecosystem functions. Despite growing insights into the mechanisms governing both the magnitude and time lags of biodiversity responses at individual levels of biodiversity, how interactions among levels of biodiversity affect ecosystem‐wide inertia in response to an environmental forcing event remains a largely unanswered question. As several sources causing time lags interact within and across multiple biodiversity levels, we hypothesise these mechanisms control how time lags at one biodiversity level may cascade into increasingly extended lags at higher biodiversity levels. We analysed empirical data on genetic diversity, species distributions, community diversity and functional diversity in semi‐natural grassland patches for the existence and length of lagged responses across biodiversity levels in response to 165 years of land‐use change. Time lags were present at all tested biodiversity levels (from genes to traits), none yet in equilibrium with the current landscape. Significant variation in delays among individual species possibly controlled by delayed loss in genetic diversity may affect the scale of future biodiversity losses at the community level. Functional diversity appeared to have the most delayed response, likely due to high functional redundancy in species‐rich grassland communities. Synthesis . Species identity seems central in governing the observed delays at each level of biodiversity, from genetic to functional diversity. In particular, species identity controls the slowest responses at the genetic level, potentially leading to accumulating underestimations of the size and duration of time lags at species, community and functional diversity levels compared to average community responses. Conservation and restoration actions must therefore anticipate the potentially systematic underestimation of time lags in biodiversity responses following habitat change to ensure their effectiveness in halting biodiversity loss.