Global Warming and Neotropical Rainforests: A Historical Perspective

There is concern over the future of the tropical rainforest (TRF) in the face of global warming. Will TRFs collapse? The fossil record can inform us about that. Our compilation of 5,998 empirical estimates of temperature over the past 120 Ma indicates that tropics have warmed as much as 7°C during both the mid-Cretaceous and the Paleogene. We analyzed the paleobotanical record of South America during the Paleogene and found that the TRF did not expand toward temperate latitudes during global warm events, even though temperatures were appropriate for doing so, suggesting that solar insolation can be a constraint on the distribution of the tropical biome. Rather, a novel biome, adapted to temperate latitudes with warm winters, developed south of the tropical zone. The TRF did not collapse during past warmings; on the contrary, its diversity increased. The increase in temperature seems to be a major driver in promoting diversity.