Each species has a limited range of tolerance to climatic variables, called its ‘climate envelope’. Inside the envelope it can live: outside it will die. As climate changes this envelope moves across the Earth’s surface and the species must also move in order to stay within it. In this paper, Richard Corlett (from XTBG) and David Westcott (from CSIRO in Australia) compare the speed at which plants can move with the speed at which they will need to move to keep up with the expected rate of climate change over the next century. Unlike animals, plants can only move once per generation, by seed dispersal. The potential speed of plant movement is determined by many factors, but the most important are the generation time and the seed dispersal distance. The fastest plants have short generation times and long seed dispersal distances. The authors estimate that most plant species can move less than one kilometre per year and many species will be much slower than this. The speed at which they will need to move will also depend on many factors, but plants will need to move fastest in flat regions of the tropics, where the climate is uniform over large areas, and slowest in steep topography, where the climate changes a lot over short distances. The authors conclude that many, possibly most, plant species on Earth will not be able to keep up with climate change. However, there is relatively better news for Yunnan, where the very steep climate gradients may make it possible for even slow-moving plants to survive, as long as their habitat is not fragmented and their seed dispersal agents are still present.