A simple effective medium theory is derived for spatially heterogeneous reaction-diffusion media.
Its validity is tested through comparisons with simulations of front and pulse propagation in systems
with spatially varying diffusion coefficients and reaction rates. The theory is able to predict wave
speeds if the characteristic front width is much larger than the length scale of the heterogeneities.
This condition is violated in media with isolated or weakly connected sites. In such media the
theory nevertheless provides good results if it predicts the percolation threshold of the involved sites