Local topography has long made the environmental picture very complicated. In areas of high relief, vegetation has differed considerably between river-valley bottoms and uplands, for example. In SW France, even during periods of glacial advance, trees requiring mild conditions survived in warmer microclimates such as south-facing slopes. In general, this rugged countryside exhibited much diversity in plant communities. The kind of broken topography seen here in SW France provided habitats for a wide diversity of animal species.