The book "Plantesamfund" was based on Warming's lectures on plant geography at the University of Copenhagen. It gives an introduction to all major biomes of the world. Warming's aim, and his major lasting impact on the development of ecology, was to explain how nature solved similar problems (drought, flooding, cold, salt, herbivory, etc.) in similar way, despite using very different ‘raw material’ (species of different origin) in different regions of the world. This was a remarkably modern view—completely different from the merely descriptive floristic plant geography prevailing during his time.