Recent human impacts on biodiversity across the planet are immense. Trying to understand and quantify how we are impacting biodiversity currently and how we have done so in the past presents methodological challenges that can be be met through the combined use of current day diversity information within a paleontological framework.
In part driven by my interest in understanding how to frame the current rates of extirpation and extinction among amphibians and in trying to think about how we can assess anthropogenic impacts from climate change, deforestation, and habitat fragmentation, I have become interested in thinking about the metrics we use to assess rates of extinction and estimate background rates of extinction. Among vertebrates amphibians are currently experiencing the greatest level of extirpation and extinction. Calculating extinction rates is more straight forward for groups that have a decent fossil record, but for groups that lack a fossil record indirect methods are needed.
Stemming from a seminar organized by Tony Barnosky, we assessed the current loss of biodiversity in the framework of the 5 previous mass extinctions. We used the IUCN RedList in combination with paleontological criteria to evaluate if the present day extinction rates have reached the magnitude of a mass extinction and found that while we haven’t crossed the threshold we are approaching it.
A. D. Barnosky, N. Matzke, S. Tomiya, G. O. U. Wogan, B. Swartz, T. Quental, C. Marshall, J. L. McGuire, E.L. Lindsey, K. C. Maguire, B. Mersey, E. A. Ferrar. 2011. Has the Earth’s sixth mass extinction already arrived? Nature v. 471: 51-57
The magnitude of human induced environmental change has sparked a debate on if we have left the Holocene behind and entered a new geologic epoch “the Anthropocene”. The Anthropocene is used to identify the time in Earth history that begins when humans become a geological force for planetary change (Crutzen 2002). Debate on the timing of this epoch, and the evidence that could be used to circumscribe it and the validity of doing so is ongoing.
Related to this debate, we asked if there are identifieable biochronologic signals that correspond to the peopling of North America and the arrival of Europeans. The North American Land Mammal Ages (NALMAs) are a well established system that relies on distinctive assemblages of mammals to subdivide geological epochs. We name two new NALMAs that span the Holocene, demonstrating the stepwise episodes of human induced ecological change in North America.
A. D. Barnosky, M. Holmes, R. Kirchholtes, E. Lindsey, K. C. McGuire, A. W. Proust, M. A. Stegner, J. Sunseri, B. Swrtz, J. Swift, N. A, Villavicencio, G. O. U. Wogan. 2014. Prelude to the Anthropocene: Two New North American Land-Mammal Ages. Anthropocene Review. v. 1: 225-242 DOI: 10.1177/2053019614547433