Barnosky et al. 2011

Has the Earth’s 6^thmass extinction already arrived?

Barnosky, et al. 2011. Nature 471: 51-57

Blog by Willow

Authors (first 3 only)

Anthony Barnosky

            PhD 1983 U.Washington

            Prof. Biology at Stanford (since 2018), Prof. Emeritus at UC Berkeley (1990-2016)

            “Ever-increasing numbers of people, climate change, and transformation of half of the planet’s land to serve humans are among the many pressures that are hallmarks of the unique time in which we now live, the Anthropocene.   My current work focuses on understanding how to guide biological systems such that they maintain vibrancy in the face of unusually rapid human-caused global changes.”

Nicholas Matzke 

            PhD 2013 UC Berkeley

Discovery Early Career Award Research Fellow at the Australian National University 

Wishes to “reintegrate” ecological and historical biogeography by looking at how environmental and ecological controls on dispersal have affected geographic range evolution through time and through phylogeny.

Susumu Tomiya

            PhD 2013? UC Berkeley

            Postdoc Des Moines University, previously Field Museum

            "I study the fossil record of North American mammals, to understand how mammalian 'communities' are assembled and how they respond to major environmental changes at the macroevolutionary time scale of millions of years."

Paper Summary

Main Question

Do current rates and magnitudes of extinction qualify as a mass extinction compared to the Big Five?

Background

            Mass Extinction- 75% of species disappear within 2 million years

            Rate- # of extinctions/time

            Magnitude- % of species that have gone extinct

            Data biases

                        Geography- fossils don’t preserve everywhere, so you can’t compare everywhere

Sampling- only taxa with identifiable hard parts fossilize, and only animals we know are threatened get studied and not all consistently

Taxonomy- fossil species are usually morphological, modern species have a much wider range of definitions resulting in many more species than possible in fossils

Underestimating extinctions- the last fossil to appear is certainly not the last individual to go extinct, not all modern species are described let alone analyzed

Time- the fossil record is highly time-averaged compared to the modern, so all modern rates must be super-scaled up 

Methods

Calculated rate, magnitude, and total extinction rate (rate plus magnitude) for the Big Five extinctions

Calculated rat, magnitude, and total extinction rate for the modern at a variety of assumptions and time scales

Results/Discussion

Modern rates of extinction is higher than background rates regardless of which IUCN animals go extinct. We are going extinct much faster than normal.

Modern magnitudes of extinction are at 20-43% of Big Five levels. We are not currently in a mass extinction.

Combined rates of extinction indicate we are going extinct slower to almost as fast as the Big Five.

If extinction rate continues, we could hit the 6^thmass extinction between 240-540 yrs (worst case scenario). Conservative estimates place the 6^thmass extinction between 4500-11000 yrs. 

Conclusions

Technically, we are not yet in a mass extinction.

If we lose the “critically endangered” species, we will be in a mass extinction.

We have “primed the pump” of extinction and, without human mitigation efforts, stressors will increase in the future and intensify the already terrifying extinction looming ahead.

Remarks

This was nice and scary for just after Halloween. I liked how this paper was set up. I found Table 1 to be very interesting. The K-Pg extinction (dinosaurs) is usually everyone’s favorite extinction, so I’ve never really read about the others. First time I read the causes, I found too many similarities with projected climate change, so I also enjoyed the section about “Perfect Storms.”  

Paper 35

35. Raup, D.M. and J.J. Sepkoski. 1982. Mass extinctions in the marine fossil

record. Science 215:1501-1503.

Blog Author: Ben Clinch

Blurb Author: Jessica Theodor

-BS, Palaeontology, University of Toronto, 1989

-PhD, Palaeontology, University of California at Berkeley, 1996

-Professor, Ecology & Evolutionary Biology, University of Calgary

-Research focuses on understanding the causes of organismal diversity patterns found over geologic time

Paper Author: David M. Raup

-BS, University of Chicago

-PhD, Geology, Harvard University

-Curator and Dean of Science at Field Museum of Natural History in Chicago

-Taught at Caltech, Johns Hopkins, University of Rochester

-Passed away in 2015

Main Question: Can we identify specific mass extinctions more accurately and comprehensively?

Background:

-Mass extinctions have been previously identified, but timing and magnitude of these events have proven difficult due to the fragmentary nature of fossil record data

-Previous familial data sets have been subjective due to taxonomic problems and stratigraphic imprecision

Assumptions:

-Family-level data assumed to be ideal compromise between sampling limitations and taxonomic uncertainty

Methods:

-Data set of marine vertebrates, invertebrates, protozoans from the Phanerozoic

-Data contains around 3300 fossil marine families, 2400 of which are extinct

-87% of extinctions resolved to stratigraphic stage, most resolved to stratigraphic series

-Plotted rates of extinction against geologic time (76 points) (Fig. 1)

-Linear regression ran for all 76 points of the graph: four points fell above 99% confidence interval, one point fell above 95% confidence interval

-Phanerozoic diversity curve compiled from familial data (Fig. 2)

Results:

-Two rates of extinction identified in the Phanerozoic: background extinction, mass extinction (points considerably higher than the background)

-Five mass extinctions clearly defined from data: Late Ordovician, Late Devonian, Late Permian, Late Triassic, Late Cretaceous

-Background extinction rate has declined over time

Conclusions:

-The decrease in extinction rate could be due to the theory that fitness optimization through evolutionary time leads to prolonged survival

-Decline in extinction rate during the Cambrian shows that the number of extinctions that did not occur was close to the amount of increase in diversity over that interval- suggests that the net increase in diversity throughout the Phanerozoic may have more to do with a decrease in extinction than an increase in origination

-Major mass extinctions have been identified as distinct from background extinction

-Data doesn’t inform what caused the extinctions

Questions/Comments:

-What does he mean by “the data benefit from compilation of taxonomic and stratigraphic investigations far beyond traditional sources”?

-What are “shelly” and “rarely preserved taxa”? Why didn’t he define these?

Community ecology in a changing environment: Perspectives from the Quaternary

Blog Author: Devra Hock

Author:

Stephen T Jackson—Director of the Southwest Climate Adaption Science Center (SW CASC) also an adjunct professor in the University of Arizona’s Department of Geosciences and an adjunct research professor in the University of Arizona’s School of Natural Resources and the Environment. 

Previously at University of Wyoming as a professor of botany and founding director of the doctoral program in ecology. Before joining the University of Wyoming in 1995, Dr. Jackson held faculty positions at Indiana University, Idaho State University, and Northern Arizona University. He is past president of the American Quaternary Association and is on the governing board of the Ecological Society of America and the editorial boards of Ecosystems, Frontiers in Ecology & Environment, and Trends in Ecology and Evolution. 

His own research employs tree rings, fossil rodent middens, and sediments from lakes and bogs to investigate how past climatic changes and human activities have affected species distributions, biodiversity, and 

Jessica L. Blois—Assistant Professor at University of California Merced, School of Natural Sciences

            Previously Assistant Professor at UC Merced in Life and Environmental Sciences; Research Assistant at the UC Museum of Paleontology. PhD from Stanford in Biological Sciences

            The overarching focus of the Blois Paleoecology Lab is investigating the relationship between species, communities, and the environment, focusing on the past 21 thousand years of life on earth in order to inform the next one hundred years and beyond. We have diverse projects, but they are generally united by a focus on spatio-temporal processes. Our work also has a strong “Conservation Paleobiology” focus, trying to understand how we can use the fossil record to inform our conservation decisions for the future.

Summary/Main Points:

1. Main Question:

            Background—Community ecology and Quaternary paleoecology are both concerned with answering similar questions: understanding composition and structure of biotic assemblages, including patterns of spatial variation and dynamics in changing environments. In spite of this, community ecology and Quaternary paleoecology are disconnected and have very little interdisciplinary work. Community ecology focuses on modern, existing species assemblages and works to understand local species interactions and consequences. Quaternary paleoecology looks at properties of past communities and how they have changed at local and regional scales, from a few thousand to 2.6 million years ago. 

            Main Questions—Provide an overview of what Quaternary terrestrial records reveal about environmental and community changes, suggest some foundations for bridging between community ecology and Quaternary paleoecology, and identify topics where the two fields can engage to mutual benefit. 

2. Ecology and Time’s Environmental Texture

            -Community Ecology: Previous ecological thought has held time as a simple, uniform dimension where ecological processes unfold against a constant environmental backdrop. Essentially, time is treated as the independent variable and ecological properties are time-dependent in their change. And while the environment itself may change, that is only due to ecological processes changing or as a stochastic variable, fluctuating randomly about a constant mean. Only recently have environmental change and nonstationary variability been explicitly accounted for in ecological models. 

            -Quaternary Paleoecology: Time is textured by environmental change and variability, suggested by a broad and apparently continuous spectrum of climate variability and change in paleoclimate records. Climate variability is rarely stationary in nature, with climate means, variances, extremes, and modalities evolving through time. There is no “normal” climate. Environmental conditions do not necessarily repeat themselves. While there are cyclic or quasicyclic events, the magnitude, spatial extent, and duration are different with each occurrence. Climate change often involves changing combinations of seasonal temperature, seasonal precipitation and other factors. Climate change can be gradual and directional, but is more often punctuated by episodic events and rapid state transitions.

3. Communities Come, Communities Go: 

            -New ecological thought that an ecological community comprises a single place that happens to be occupied by an assemblage of species with overlapping distributions and environmental tolerances. Therefore, community concept should be replaced by the spatial distributions of populations. 

            -Paleoecological records support a parallel conception, though involving time. An ecological community can be viewed as a single point in a spatial framework of species distributions overlapping environmental gradients and responses to environmental change and variability over time. Spatial distributions evolve through time and contingent on temporal processes, while temporal patterns of occurrence and abundance at individual sites are contingent on spatial distributions, patterns, and processes. 

            -Illustrative example of changing compositions of forest communities in the records of the past 8,600 years at Tower Lake in Central Upper Michigan.  The modern forest community has only existed as it is for the past 1,400 years. Furthermore, no forest community has persisted there for longer than 1,500 years. Another example is the 86,000 year pollen record of Lake Peten-Itza in Guatemala. The community observed at any single point in time is ephemeral, rarely persisting for more than a few millennia before being replaced by something new. These same patterns apply to terrestrial insect and vertebrate communities, which show changes in species abundances, range shifts, extirpations and colonizations, and extinctions. 

4. What Governs Community Assembly and Disassembly?

            -Community Ecology: Three modal concepts that determine community structure and composition: interaction assembly, environmental assembly, and neutral assembly. Interaction assembly is deeply rooted in community ecology, emphasizing Eltonian niche, which considers communities to be structured primarily by strong interactions among species. Resource competition is considered a main interaction, though others include facilitation, mutualism, and trophic relationships. Environmental assembly consider communities to be structured primarily by species’ physiological and demographical responses to the physical environment. It is also niche based, but emphasizes the Grinnellian niche, which supports species’ having finite environmental requirements or tolerances. Neutral assembly considers communities to be structured by random processes, such as dispersal, recruitment, and mortality. 

            -Quaternary Paleoecology: Strongly supports environmental assembly, based on both theoretical and empirical foundations. Paleoecologists look towards environmental change, particularly climate change, as the main driver of community dynamics. Comparisons with paleoenvironmental records and paleoclimate simulations justify environmental assembly, and most paleoecologists do not look for any other drivers of community dynamics. 

            -Environmental change is powerful, and should be incorporated more explicitly into community ecology. 

-Species interactions govern the community outcome of environmental change and should be considered more explicitly in paleoecological explanation

5. Spanning the Missing Middle

            -The missing middle Quaternary of ecological history provides abundant opportunity for collaboration between paleoecologists and community ecologists. Paleoecologists must understand the ecological questions that they are applying to their data. On the flip side, ecologists must understand the nature of paleoecological data and inference. Particularly, careful consideration must be paid to scale and taphonomy. 

            -Identify a nonexhaustive set of themes, topics, and questions on which collaborations might be entered:

·     Community Assembly and Disassembly

·     Trait Based Community Patterns

·     Diversity Dynamics  Through Time

·     Ecological Rules in the Anthropocene

·     Dynamics of Regional Species Pools

·     Clocking Time-Dependent Processes

6. Conclusion

            -We live in a time of rapid environmental change, with novel communities and ecosystems already widespread and increasing globally. Integrating mechanisms of community ecology and empirical richness of paleoecology will advance the general field of ecology, but will also increase its capacity to contribute to climate change adaptation and minimize risks to biodiversity and ecological services. 

Questions/Comments:

             Overall, I liked the way the authors formatted this paper, discussing particular ecological concepts and comparing how modern community ecology and paleoecology tackle those different concepts. I especially appreciated their informative figures, (fig. 1, fig. 4), as I think both figures demonstrated and illustrated the concepts outlined in the text. I also liked the authors consideration for areas that would benefit from a better combination of paleoecology and community ecology. While I do think that the interdisciplinary research would lead to better understanding of how species and communities react to change, I think the grandiose statement at the end takes that a tiny bit too far, though that is standard for some papers. 

            Can you think of any research (modern or older) that does a good job combining modern community ecology with paleoecology? Does it fit within any of the themes suggested in this paper? 

            I also would have liked to see a few more examples with real data. The authors talk about how all of the ecological processes apply to terrestrial communities, inverts or verts, but do not show any clear examples of that. 

Paper 27

Paper 27

Blog Author: Alex Shupinski

Authors: Christopher Bernabo 

Thompson Webb 

I received a botany degree from Swarthmore and a PhD in atmospheric sciences from the University of Wisconsin-Madison. In 1972, I joined John Imbrie and R.K. Matthews to study Quaternary climates, as CLIMAP was starting. I added a terrestrial paleoclimate and paleovegetation focus to their paleoceanographic perspective on earth system history. Once COHMAP (Cooperative Holocene Mapping Project) began in 1977, I worked with colleagues at Wisconsin, Minnesota, Oxford, Durham, Lamont, Brown, and Oregon to compile large data sets, to interpret them in climate terms, and to compare the results with climate-model simulations of the past 21,000 years. Key results appeared in Science in 1988, in a joint-edited book in 1993 and in an issue of Quaternary Science Reviews in 1998. In 1996, I and Jeff Donnelly began studying the sedimentary record of land-falling hurricanes. I retired in 2005 and continue teaching in Summer and Continuing Studies at Brown.

Introduction

-Pollen data was mapped in northeastern North America 

-Studying Holocene vegetation

-Five categories: pine, oak, spruce, herbs and BAFT group

The Data Base

-Data was obtained from published sources

-computer programs calculated the pollen percentage data

-300 pollen types identified

-Radiocarbon dates on cores determined depth, most cores had sediments throughout the Holocene

-Average of four dates per core

-62 sites with the greatest changes occurring between 11,000 and 7,000

Construction of the Maps

-Isochrone maps show the movement of pollen species and a time period

-Isopoll maps demonstrate patterns in the pollen frequency across the distribution

-A sequence of events was created 

-Maps were created of modern distributions for the identified pollen and then a numerical comparison was used using Pearson product-moment correlation coefficient

Description of the Holocene Pollen Maps

-Spruce reduced in abundance around 11,000.  Pine increased in northern regions, oak increased in the southern regions. Spruce no longer dominated and herb pollen was reduced showing a more closed forest.

-10,000 the spruce was replaced by pine.  By 9,000 it was no longer a major pollen found and by 8,000 it was a minor element of the region

-Laurentide ice sheet collapsed around 8,000 and spruce pollen was gone from the south  and pine and oak shifted farther north.

-As time continued the change in pollen patterns was more gradual up until 4,000.  BAFT pollen  increased at the expense of pine changing.

-Between 4,000 and 2,000 the gradient between arboreal and nonarboreal pollen increased in the Midwest.

-Up until 500 right between vegetation changed due to European settlement the vegetation tended to change only on a local level.  Since this time the vegetation change is mainly due to human activity. Herbs increased due to agriculture.

-Final glaciation showed the greatest change in pollen movement.

Four Major Changes

-Spruce declined

-Pine moved westward, beech and hemlock moved to the great lake region around 8,000.  Hardwood forests shifted north. 

-Hemlock, Birch, Maple and Beech all expanded their ranges.  BAFT becomes dominant in New England

-Prairie development occurring the Midwest over 11,000 years ago and began to move east around 10,000 to 9,000 and then receded westward up until 2,000

Conclusion

-Major vegetational shifts and patterns were able to be tracked using the pollen data

-Mixing of pollen in the air took away fine scale changes and taxonomy was general

-The cartographic approach provided visual aids to demonstrate the patterns

-Areas of steep gradients in vegetations should be studied more closely with more densely spaced sites

-This study will provide a framework for future studies to better understand the vegetational history of North America

Thoughts: 

The authors recognized the flaws in the strategies they used but provided more types of criteria to be used and combined when analyzing pollen data which is important in understanding the entire ecosystem of North America.  This paper would help to improve future studies looking at pollen data. I also felt it was very well-written and easy to follow, which is important for any paper to be influential. The methods was a bit boring to read but I think the level of detail we can obtain is fascinating and the history of our vegetation is very interesting to me.  

Paper 21

Pg 377

Paper 21- Graham 1986

Graham R.W. 1986. Response of mammalian communities to environmental changes during the late Quaternary. Pages 300-313 in J. Diamond and T.J. Case, eds., Community Ecology. Harper and Rowe, New York

Blog Author: Angel Sumpter

Blurb Author: S. Kathleen Lyons

●     B.S. Wayland Baptist University, 1991

●     Ph.D. at University of Chicago in 2001

●     Currently an assistant professor of biological sciences at the University of Nebraska.

●     “I am interested in the factors affecting and controlling species diversity at multiple scales across both space and time. Moreover, I am particularly interested in the effects of global climate change on species diversity and use the fossil record of mammals over the last 40,000 years to evaluate how current changes in global climate may affect diversity patterns in the future. Because it provides a useful way to compare modern species and communities to fossil species and communities, I focus on the similarities and differences in macroecological patterns across space and time.”

Paper Author: Russell W. Graham

●      Professor, Museum Director

●     Ph.D., University of Texas at Austin, 1976

●     Research Interest: Vertebrate Paleontology, Quaternary Vertebrate Paleontology, Taphonomy, and Neotoma Paleoecological Database.

Main Question

●     Background

○     Approximately 18,000 years most of the midwestern US and Canada were covered in ice. Once ice started to melt about 8000 years afterwards, ice glaciers only occupied miniscule portions of Canada. Over time this continued during the Pleistocene. Data shows various stages where ice was high, then lower, and somehow alternated between the two. For this reason various species shifted their ranges.

●     Question

○     How ancient are modern ecological communities?

○     Is it likely that species that coexist today have had a long continued history of opportunity for coevolutionary adjustments to each other?

Methods

●     Compared fossil communities at different times to one another, but tried to eliminate some of the bias that comes along with sampling bias by focusing on four primary taphonomic factors.

●     Depositional  Environments

○     Used faunas from low-energy environments or caves due to the fact that these environments establish more of a complete sample of all of the components of the fossil community and a better representation of the local environments.

●     Agents of Bone  accumulation

○     Mammalian taxa was restricted to certain species densities.

●     Rates of Sedimentation

○     Used environments with rapids rates of sedimentation because it provided the greatest  temporal separation of events.

●     Postdepositional  Disturbances

○     Mixed fossil assemblages were excluded from the data because postdepositional disturbances such as chemical break down in soils and bioturbation can cause mixing of of deposits of different ages and this cause artificial fossil assemblages that do not represent biological communities.  

Results

●     As far as individualistic response goes vegetation, disease, and other interactions may have overridden any direct effects of climate change. This could be the main reason why a lot of the communities are similar to the present day except for the megafauna extinction. Unfortunately this may have been a consequence of human interactions.

Conclusion

●     After gathering extensive amounts of data and finally comparing Pleistocene and Holocene communities, the only true qualitative difference is that the Pleistocene megafauna is extinct. The reality of the matter is that this is due to many changes in the environment and communities themselves. As a result of these changes, many  communities completely reshuffled themselves meaning southern species became more north, as northern species became more southern. They think these drastic environmental changes are the main reason the Pleistocene megafauna became extinct, however, they can not validate their suspicion. What they can validate is that many small animal ecosystems have definitely changed since the Pleistocene.

Comments

●     Interesting topic and research, but as results show, theirs not too much quantitative data.

●     I feel like doing this to see how ancient modern communities are was wrong, and didn’t do much in terms of providing new information used to better the experiment.