Thanks to Janet Franklin for this guest post on their recent paper! Really interesting to think back through these historical changes.
During the last Ice Age, the islands of the Bahamas were cooler, drier, and much larger than today because sea level was over 100 m lower. The Bahamas also were much closer to the Greater Antillean islands of Cuba and Hispaniola. Thousands of beautifully preserved bird fossils from dry and water-filled caves on the island of Abaco in the Bahamas have allowed us to reconstruct the bird community found there during the last Ice Age (10,000 or more years ago) and compare it with the birdlife on Abaco today.
More than half (25 of 45) of the bird species known to Abaco during the Ice Age no longer live on the island, including various hawks, rails, snipe, nightjars, woodpeckers, and swallows. Also among these 25 species are some that now live in more temperate climates and open habitats, such as the Eastern Bluebird and Eastern Meadowlark. This is what we might expect – that the profound global climate changes that took place as the great continental ice sheets melted would have affected where species can live. Nevertheless, 20 species (from pigeons to parrots to pine warblers – see photos) found as Ice Age fossils still live on Abaco today with its more tropical climate. Furthermore, a diverse set of species (hawks, owls, pigeons, and songbirds) persisted through the major climate change at the end of the Ice Age, but did not survive the past millennium of human presence on Abaco.
This study of ancient birdlife on a tropical island helps us to understand how modern climate change may affect biodiversity, whether on continents or islands. Living species vary considerably in how great a range of climate conditions they can tolerate, with some being very sensitive to changes in temperature and rainfall, and others less so. Regardless of climate change, many species also are affected by the profound environmental changes that take place when humans arrive, clear land, use fire, and bring predators (including themselves) into naïve ecological communities. It is this double-whammy of climate change and direct human impact on the environment that makes us so justifiably concerned about the future of plant and animal life on our planet.
This research was sponsored by the National Science Foundation, Geography and Spatial Sciences Program.
Janet Franklin, School of Geographical Sciences and Urban Planning, Arizona State University
David W. Steadman, Florida Museum of Natural History, University of Florida