Botanic gardens are organized around plant collections, and climate change will affect those collections. Land loss is expected for gardens near sea level, prompting a loss of plants from the collection. Future collection development requires planning for these losses, which in turn requires assessment of the extent and rate of collection loss. Contributors to this article examined collection inventory change over time using records at Montgomery Botanical Center (MBC), to formulate a plant collection half-life concept. This half-life was used to project changes in MBC’s plant collection over the next 100 years within the context of sea level changes. Comparing predicted rates of collection change with projected rates of loss due to sea level rise, we expect plant collection development to keep pace with climate change. As actively curated resources, botanic garden plant collections can adapt to environmental change faster and more deliberately than natural systems.