Is second-growth rainforest good enough? Going beyond community composition

Tropical rainforests are the most biodiverse terrestrial ecosystems on the planet. Since so much old-growth rainforest continues to be destroyed, much effort has gone into understanding the conservation value of second-growth rainforests. However, the primary measuring stick for old-growth/second-growth comparisons is overall community similarity, and while presence-absence or abundance metrics are important initial data, it is also vital to determine whether species that are present in second-growth rainforests are actually viable, self-sustaining populations. To address this question, we assessed glass frog communities in old and second-growth rainforests at ten study sites in two countries. We compared: (1) glass frog community similarity, (2) patterns of species abundance, (3) embryonic survival, (4) reproductive success and (5) abiotic conditions in old and second-growth rainforests. Results indicated that glass frog community composition was consistently similar and that abundances did not differ between forest types for any species. No species were restricted to old-growth. Similarly, short-term embryonic survival was not significantly different between old-growth and second-growth forests. For one species that was intensively studied (H. orientale tobagoense), female clutch size was not significantly different among forest types and male reproductive success was significantly higher in second-growth. Our work suggests that glass frog communities in second-growth rainforests are similar to old-growth and are likely viable and self-sustaining populations. Conserving remnant old-growth forests remains vitally important but it is becoming clear that protecting second growth is also an important strategy to conserve biodiversity in the face of today’s unprecedented environmental challenges.