We consider a natural population facing a climate change. To survive, this population can adopt two strategies: migration towards colder regions, or a phenotypic evolution, to become capable to cope with warmer temperatures. In the case of asexual populations, the framework of monostable parabolic equations provides powerful results to describe the dynamics of the species. The parabolic equations that appear in this context present several difficulties, and describing their dynamics required the development of some new methods, involving in particular Harnack inequalities. We will illustrate the quantitative estimates we derive with some specific ecology questions where these methods could provide an interesting insight.