For decades, botanists have recognized that rare plants are clustered into ecological “islands”: small and isolated habitat patches produced by landscape features such as sinkholes and bedrock outcrops. Insular ecosystems often provide unusually stressful microhabitats for plant growth (eg because of thin soils, high temperatures, extreme pH, or limited nutrients) to which rare species are specially adapted. Climate-driven shifts to these stressors may undermine the competitive advantage of stress-adapted species, allowing them to be displaced by competitors, or may overwhelm their coping strategies altogether. Special features of insular ecosystems—such as extreme habitat fragmentation and association with unusual landscape features—may also affect their climate sensitivity and adaptive capacity. To predict and manage these changes, a simple conceptual framework is presented based on a synthesis of over 300 site-level studies. Using this framework, conservation efforts can leverage existing ecological knowledge to anticipate changes in particular microhabitats and design targeted strategies for conserving rare species.