  The magnitude and variability of Earth's biodiversity have puzzled scientists
ever since paleontologic fossil databases became available. We identify and
study a model of interdependent species where both endogenous and exogenous
impacts determine the nonstationary extinction dynamics. The framework provides
an explanation for the qualitative difference of marine and continental
biodiversity growth. In particular, the stagnation of marine biodiversity may
result from a global transition from an imbalanced to a balanced state of the
species dependency network. The predictions of our framework are in agreement
with paleontologic databases.
