The study of biodiversity has grown exponentially in the last thirty years in response to demands for greater understanding of the function and importance of Earth's biodiversity and finding solutions to conserve it. Here, we test the hypothesis that biodiversity science has become more interdisciplinary over time. To do so, we analyse 97,945 peer-reviewed articles over a twenty-two year time period (1990 - 2012) with a continuous time dynamic model, which classifies articles into concepts (i.e., topics and ideas) based on word co-occurrences. Using the model output, we then quantify different aspects of interdisciplinarity: concept diversity, i.e. the diversity of topics and ideas across subdisciplines in biodiversity science, subdiscipline diversity, i.e. the diversity of subdisciplines across concepts, and network structure, which captures interactions between concepts and subdisciplines. We found that, on average, concept and subdiscipline diversity in biodiversity science were either stable or declining, patterns which were driven by the persistence of rare concepts and subdisciplines and a decline in the diversity of common concepts and subdisciplines, respectively. Moreover, our results provide evidence that conceptual homogenization, i.e. decreases in temporal concept diversity, underlies the observed trends in interdisciplinarity. Together, our results reveal that biodiversity science is undergoing a dynamic phase as a scientific discipline that is consolidating around a core set of concepts. Our results suggest that progress towards addressing the biodiversity crisis via greater interdisciplinarity during the study period may have been slowed by extrinsic factors, such as the failure to invest in research spanning across concepts and disciplines. However, recent initiatives such as the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) may attract broader support for biodiversity-related issues and hence interdisciplinary approaches to address scientific, political, and societal challenges in the coming years.