An information-theoretic comparison of the topologies of observed ecosystem transfers and randomly constructed networks reveals that it is not easy to separate the members of the two sets. The distribution of ecosystem flow magnitudes, however, is seen to differ markedly from ordinary probability functions and to resemble the Cauchy or Pareto distributions. The agencies that impart such structure to ecological flow networks are not obvious, but one strong possibility is that autocatalysis, or indirect mutualism, promotes certain pathways at the expense of others, thereby enlarging the tail of the distribution of flow magnitudes.