  We motivate and analyze a simple model for the formation of banded vegetation
patterns. The model incorporates a minimal number of ingredients for vegetation
growth in semi-arid landscapes. It allows for comprehensive analysis and sheds
new light onto phenomena such as the migration of vegetation bands and the
interplay between their upper and lower edges. The key ingredient is the
formulation as a closed reaction-diffusion system, thus introducing a
conservation law that both allows for analysis and provides ready intuition and
understanding through analogies with characteristic speeds of propagation and
shock waves.
