Most plant species rely on seeds for recruitment and persistence in the landscape. Local environments have a strong influence on seed germination and so shifts in temperature and moisture caused by rapid environmental change may affect when, where and whether plants will recruit. Small increases in temperature, changes to rainfall seasonality or slight reductions in moisture availability during the growing season may threaten populations of some plant species. Impacts of changing environmental conditions on seeds have already been documented and include reduced germination with soil warming, shifts in the timing of germination, reduced seedling survival and shortened survival of seeds in the soil. Global climate change will also alter fire regimes, in turn leading to probable declines in seed production, seedling survival and seed-bank viability. Although episodic disturbances like fire are normal in some systems, providing recruitment opportunities, changed environmental conditions may radically alter vegetation characteristics and composition. Shifts in the timing of germination will influence population dynamics, community composition and species geographic ranges. Some species will face a high risk of local population extinction, possibly leading to biodiversity decline over time. Together these changes may require modification to seed use in agriculture and in ecological restoration. Species with germination strategies that vary among individuals or across populations may be more robust and ultimately have a lower extinction risk. Although there is strong evidence that plant species and communities are threatened by climate change through effects on recruitment, currently, we do not know for sure which communities are most at risk. Planning for unexpected seed responses to global warming, particularly in vulnerable ecosystems already experiencing wide temperature and moisture extremes, may require ex-situ seed conservation and assisted plant migration.