Abstract Given , we prove that there exists depending only on so that if is a metric graph of rank with metric entropy 1, then there exists a proper subgraph of with metric entropy at least . This answers a question of the second two authors together with Rieck. We interpret this as a graph theoretic version of the Bers Lemma from hyperbolic geometry, and explain some connections to the pressure metric on the Culler–Vogtmann Outer Space.
Hamed et al. (2026) studied this question.