What does climate change mean for New York City?

Impact of climate change on New York City’s coastal flood hazard: Increasing flood heights from the preindustrial to 2300 CE

Andra J. Garner, Michael E. Mann, Kerry A. Emanuel, Robert E. Kopp, Ning Lin, Richard B. Alley, Benjamin P. Horton, Robert M. DeConto, Jeffrey P. Donnelly, David Pollard

Data and Methods: This study employs various models to understand the future impact of climate change from tropical cyclones. These cyclones create storm surges, which are abnormal rises in water that often lead to flooding. To model storm surge heights in the past (1970-2005), this study uses data from about 5,000 storms. For predicting future storm characteristics for the next few centuries, the study assesses about 12,000 storms. Researchers use storm data to run a variety of simulations that have varying parameters. For example, they can modify the trajectories and wind speeds of tropical cyclones, and the frequencies and intensities of storms to model different scenarios.

They then used the storm models to quantify potential flooding in New York City by combining estimates of storm surge heights with anticipated sea level rise. Such changes in sea level are governed by mass loss of glaciers and ice sheets, thermal expansion, ocean dynamics, and water storage on land. Again, they modified these parameters in a number of models to predict flooding from future storm surges. This study focuses on two specific scenarios from previously developed models: Representative Concentration Pathway (RCP) 4.5 and 8.5. Various modifications to RCP4.5 and RCP8.5 are used to make predictions about the future of storm-related flooding in New York City.

FIgure 1. Projected sea level rise from present day to 2300. Climate projections RCP4.5 (yellow) and RCP8.5 (orange) have much lower projections than the red and maroon projections that represent enhanced Antarctic Ice Sheet melt. By 2300, sea level near New York City could rise by a maximum of 15.7 meters (51.5 feet).

Results: This group found that the maximum wind speeds of tropical cyclones in the future are much greater than the maximum speeds we see today. From this they conclude that future tropical storms will be much more intense, and the storm surges that reach New York City will be greater. They also found that the tracks of tropical cyclones will shift with time, and the density of tracks near New York City will increase.

For the next century, this study estimates sea level rise for New York City to be between 0.55 and 1.4 meters (Figure 1). From 2100 to 2300, they predict possible rises of 1.5 to 5.7 meters. If they increase the potential ice loss from the Antarctic Ice Sheet, those values drastically increase to a maximum sea level rise of 15.7 meters by 2300. Remarkably, these values simply estimate relative sea level rise without the added effect of storm surge. Toward the end of this century (2080 to 2100), flood heights are expected to be 0.7 to 1.4 meters higher than modern New York City floods (Figure 2). By 2300, storm surges could cause floods that are 2.4 to 13.0 meters higher than modern values.

Figure 2. These four different models show flood height versus density. Each model compares modern heights to RCP4.5, RCP8.5, and both scenarios with enhanced Antarctic Ice Sheet melt. With all models and all scenarios, the average flood height is expected to increase.

Why is this study important? At present, an increase in the intensity and frequency of storms would have a negative effect on coastal zones like New York City. However, in a future with higher sea levels, the effects of tropical cyclones and storm surges could be catastrophic. Continued emissions of greenhouse gases, rising temperatures, and consequential melting of ice will create a future with significantly higher sea levels. As storms develop and create surges of higher water, their resulting floods will be larger than anything New York City–or any other city–has seen before. Comprising of nearly 50 million built square meters and over 8 million people, this coastal city is a climate change target. The hazards associated with sea level rise in such a large and populous area are unimaginable. This study only looked at the effects on this one city; but there are places around the world that risk losing everything to climate change and sea level rise.

The big picture: Sea level will rise as human-driven climate change continues to warm global temperatures and melt ice sheets. The combined effects of higher sea levels and more intense tropical cyclones will create storm surges with the potential for catastrophic flooding in major cities like New York.

Citation: Garner, A.J., Mann, M.E., Emanuel, K.A., Kopp, R.E., Lin, N., Alley, R.B., Horton, B.P., DeConto, R.M., Donnelly, J.P., and Pollard, D., 2017. Impact of climate change on New York City’s coastal flood hazard: Increasing flood heights from the preindustrial to 2300 CE. PNAS. DOI: 10.1073/pnas.1703568114

New echinoderm fossils from Anticosti Island, Quebec

Late Ordovician (Hirnantian) diploporitan fauna of Anticosti Island, Quebec, Canada: implications for evolutionary and biogeographic patterns

Sarah L. Sheffield, William I. Ausich, Colin D. Sumrall

What data [were] used? New fossils found from Anticosti Island in Quebec, Canada.

Methods: New fossils of poorly understood echinoderm (relatives of sea stars) fossils discovered from Upper Ordovician (445-443 million years ago) rocks were analyzed and compared with middle Silurian (434-428 million years ago) to better understand biogeographic and evolutionary trends.

Results: The Holocystites Fauna is a group of poorly-understood diploporitan echinoderms (a term that just means they breathe out of sets of double pores found on their body) that scientists assumed to have only lived in the midcontinent of the United States (e.g., Tennessee, Iowa, Indiana, etc.) during a very specific time within the Silurian. New fossil species Holocystites salmoensis, however, tells us that they actually also lived during the Late Ordovician of Canada, which extends their known range nearly 10-15 million years!

This fossil of Holocystites salmoensis represents a very important new datapoint that helps scientists understand poorly known echinoderm transitions from the Late Ordovician to the Silurian. A. The mouth area of Holocystites salmoensis. B. a close up of the diplopore respiratory structures. C. A line drawing of the mouth area of Holocystites salmoensis. D-E. Other fossils of Holocystites salmoensis and (F) an unidentified diploporitan found in the same deposit (Sheffield et al., 2017).

Why is this study important? So at first glance, this paper might not seem so important-it’s just one new fossil of a relatively rare group of echinoderms. What is so important about this is the time in which these fossils were found. Rocks from the Upper Ordovician, during which this fossil was found, are very rare because the ocean levels were very low. Earth was in an ice age, so a lot of ocean water was taken up in glacial ice. When sea levels are low, fewer rocks are preserved; therefore, fossil data from low sea levels are rare. Evolutionary transitions of fossils from the Ordovician through the Silurian aren’t well understood. Now that we’ve found evidence of Ordovician Holocystites, we can infer a lot more about when and how these organisms evolved.

The big picture: Crucial information about how life on Earth evolved is often hard to find from times like the Late Ordovician. Actively searching for rocks during these times and identiying fossils from within them can tell us a lot about how past life responded to mass climate change (like ice ages and significant warming periods). It can also tell us a lot about how organisms expanded and shrunk their biogeographic range. Even one new fossil, like the one identified in this paper, can change a lot about what we think we knew!

Citation: Sheffield, S.L., Ausich, W.I., Sumrall, C.D., 2017. Late Ordovician (Hirnantian) diploporitan fauna of Anticosti Island, Quebec, Canada: implications for evolutionary and biogeographic patterns: Journal of Canadian Earth Sciences, v. 55, p. 1-7, doi: 10.1139/cjes-2017-0160

New data suggests Louisiana coast is sinking at an accelerated rate

A new subsidence map for coastal Louisiana
Jaap H. Nienhuis, Torbjörn E. Törnqvist, Krista L. Jankowski, Anjali M. Fernandes, and Molly E. Keogh

Data: Data for this study was collected by another study (with a lot of the same authors) by Jankowski et al. (2017). The data is small-scale changes in wetland surface elevation – this simply means how high or low the wetland is compared to the water table.

Methods: These authors used a new technique through the Coastwide Reference Monitoring System (CRMS) program. They used long steel rods called surface-elevation-marker horizon records – in this case these rods had been in place for 6-10 years and allows the scientists to calculate how quickly the coastline is sinking (sinking of land is called subsidence). This working group also used GPS time series (data from GPS collected over a period of time) of stations below the land surface to capture deeper sinking.

Results: Their results are clearly visualized in the map of the coastline. The results indicate that there is a widespread area of subsidence (sinking) recorded at the land surface and that the rate of sinking is relatively uniform across coastal Louisiana. The results presented in this study are considerably higher than in other recent studies that have used other methods.

This subsidence map for the coastal Louisiana area is based on observational data (all of the black dots) for the last 6-10 years. The areas that are in white or gray were excluded from the analysis. These areas are either cities or agricultural areas, which have modified drainage systems (such as underground sewer systems). The warmer colors indicate increased rates of subsidence. 

Why is this study important? The gulf coast has experienced substantial wetland loss. These low-elevation coastal zones (LECZs) are very sensitive regions considering the recent rises in sea level, which are driven by the increasing climate change. In order to understand the acceleration of wetland loss, it is important to understand what has happened in the recent past. Scientists can then use this data to predict the migration of the coastline and help prevent damage and loss of life.

The big picture: These new techniques for exploring data in low-elevation coastal zones can now be applied to other locations in the world. With more scientists exploring changing coastlines, there will be a greater understanding on how sea-level rise will affect humanity in the near future.

Citation: Nienhuis, H. J., Törnqvist, T.E., Jankowski, K.L., Fernades, A.M., and Keogh, M.E. A new subsidence map for coastal Louisiana. GSA Today, vol. 27. DOI: 10.1130/GSATG337GW.1

How Did Horses Get to Just One Toe?

Mechanics of evolutionary digit reduction in fossil horses (Equidae) *
Brianna K. McHorse, Andrew A. Biewener, Stephanie E. Pierce
Summarized by Time Scavengers contributor, Maggie Limbeck

What data were used? This study used metapodials (toe bones) from 12 fossil horse genera as well as from a tapir (herbivorous mammal that looks similar to a pig, but that also has an odd number of toes) to collect data. The metapodials were imaged in cross sectional views to determine load strength (how was weight distributed among the main three toes of fossil horses and the one toe of recent horses) and geometry of the metapodials.

Methods: The metapodials from the fossil horses and tapir were micro-CT scanned (3D x-ray scanning, like the human procedure but on a smaller scale) and the images were manipulated to see the cross sectional area and other views using the open source program ImageJ with the plugin BoneJ. The images were then measured and corrected for evolutionary changes using the open source statistical software, R. Estimates for bone stress were calculated using a toe reduction index (TRI), reconstructed body weights, and angle of metapodial during ground reaction at two speeds of forward locomotion. Additionally, the amount of stress that the metapodials could support was estimated using beam mechanics (an engineering process that looks at how much stress a hypothetical beam could withstand before bending and/or breaking).

Results: Looking at the geometry of the metapodials, it was determined that as the fossil horses grew in both size and weight, their need for four front and three back toes was decreased, and as such the digits gradually decreased to one on all four limbs. For the stress experiments, as the fossils moved forward in time to recent horses, it is seen that the amount of stress that can be placed on metapodial III (what we see expressed as the hoof) increases through time and the dependence on the two metapodials on either side of digit III decreases. This statement is true for both front and back metapodials at both a moderate speed (trotting) and performance (acceleration, jumping).

Figure 1. Image of the toe reduction index (TRI) shown across a phylogenetic tree (evolutionary tree) with the cross sectional view of the metapodial being analyzed. Based on the TRI it is apparent that there is a gradient for toe loss and that there is only one genus of horse, Equus, that truly has one toe. You can also see that for those early horses that still had side toes that the shape of the toe in cross section has a much different shape and therefore still needs side toes to some extent.

Why is this study important? This study is important because it supports two hypotheses that were held about digit reduction in horses. That a) the increased body mass of horses selected for a single, strong metapodial and b) that as horses grew taller, the cost of speed from the side toes outweighed their use in stabilization. This also contradicts the commonly held belief that horses experienced digit reduction as an adaptation to the replacement of forests by grasslands.

The big picture: The big picture here is sort of two-fold. Digit reduction in tetrapods (four-legged creatures) has been of interest to many scientists because as tetrapods emerged onto land 5, 8, even more digits was the ancestral state for these organisms. As we see today, that is not the case. The vast majority of the organisms that we think of have 5 or less digits on their hands and feet, so we want to understand what drove the process of digit reduction in every animal. Second, this study highlights that it is important to keep testing hypotheses even if they have been held for a while. The additional lines of evidence provided by this study give more credibility to two commonly held hypotheses while continuing to falsify the common explanation for digit reduction in horses.

Citation: McHorse BK, Biewener AA, Pierce SE. 2017. Mechanics of evolutionary digit
reduction in fossil horses (Equidae)
. Proceedings of the Royal Society B 284: 20171174.

*all samples in this study were fossils, no live animals were used

Ancient hydrothermal seafloor deposits on Mars

Ancient hydrothermal seafloor deposits in Eridania basin on Mars
Joseph R. Michalksi, Eldar Z. Noe Deobrea, Paul B. Niles, and Javier Cuadros
Summarized by Mike Hils

What data was used? High resolution imaging and spectroscopy data about mineralogy and geology

Methods: Used data from instruments on the Mars Reconnaissance Orbiter, a satellite currently orbiting Mars:

    HiRISE (High Resolution Imaging Science Experiment) was used to define the ancient basin boundaries and to inspect the types of features and rocks located in the Eridania basin. HiRISE is a camera onboard the Mars Reconnaissance Orbiter than can resolve objects to about a foot long on the surface of Mars.

    CRISM (Compact Reconnaissance Imaging Spectrometer for Mars) to study the minerals and rocks found in the Eridania Basin. Materials bounce light off of them in a consistent pattern and energy, and spectrometers can analyze that light and identify the material on Mars’ surface.

Results: The Eridania Basin was probably up to 1.5 km (0.9 mi) deep, and flowed into a canyon named Ma’adim Vallis. Images from HiRISE show that the western half of the basin consists of massive stone that lacks bedding planes and has eroded into buttes and mesas. The basin would have held about as much water the Caspian Sea on Earth currently does. This basin is shaped different than many of the other Martian basins, and it is thought that a covering of ice kept sediment from settling on the bottom. A comparison of the craters in this part of the basin suggest that these rocks are about 3.77 Ga (G = giga, SI prefix for billion, a = annum, Latin for year) old.

Analysis from CRISM found evidence of minerals and rocks associated with deep ocean water on Earth, including iron and magnesium rich clays, serpentinite, carbonates, and chlorides. For example, serpentinite, a metamorphic rock that looks like green marble, forms when basalt reacts with warm, deep sea water. Carbonate minerals are common on Earth in the form of limestone, marble, seashells, and corals. The authors suspect that the carbonate formed due to hydrothermal interactions. Chlorides, such as salt (sodium chloride), form on Earth when water evaporates.

Map of the Martian terrane with colors indicating highs (orange) and lows (blue) of an ancient sea. The data points in the legend are minerals that were identified at each location.

Why is this study important? This study is important in two ways. First, one idea for the origin of life on Earth is that it developed around hydrothermal vents in the ocean. Although ancient rocks have been found suggesting such environments in the past, they have been significantly altered by weathering and metamorphism, and vital information has been lost. Martian sites, which haven’t been altered nearly as much as Terrestrial ones, might be a good proxy for understanding early environments on Earth. Secondly, the identification of such sites on Mars could provide key places to look for signs of life on Mars.

The big picture: Understanding how life began is a huge problem that scientists in many fields are exploring. Life may have evolved on Earth, or it may have arrived here from some other body. The identification of hydrothermal environments on Mars would allow scientists to gain a better understanding of hydrothermal environments on Earth as life was evolving and try to see if life could have started here. This would also allow astrobiologists to look for evidence of extraterrestrial life on Mars.
Two other bodies in our solar system may harbor life around hydrothermal vents. Jupiter’s moon Europa and Saturn’s moon Enceladus are both covered in salty water capped with ice, and both experience tectonic activity due to the gravitational pull from their host planets. In addition, organic molecules (chemicals made mostly of carbon that are often associated with organisms) have been detected in water escaping from Enceladus. If life could have evolved in hydrothermal environments on Earth and Mars, it is likely Europa and Enceladus both host extraterrestrial life now.

Citation: Michalski, J., Dobrea, E., Niles, P., Cuadros, J. 2017. Ancient hydrothermal seafloor deposits in Eridania basin on Mars. Nature Communications, 8:15978. doi: 10.1038/ncomms15978

Rapid decline of vertebrate populations

Biological annihilation via the ongoing sixth mass extinction signaled by vertebrate population losses and decline

Gerardo Ceballos, Paul R. Ehrlich, and Rodolfo Dirzo

Global data from the study of terrestrial species. Species richness (maps on the left) indicates the number of species; number of decreasing species is presented on the middle maps; percentage of decreasing species is presented at right. The top 3 maps are for all vertebrate animals, and the lower maps are separated my the major groups (mammals, birds, reptiles, and amphibians). The cooler the color on the percentage decreasing maps, the more severe the loss of those animals.
Data: The scientists used a large data set of vertebrate populations (27,600 species and a more detailed data set of 177 mammal species from 1900 to 2015) to examine how the ranges of vertebrate animals have become smaller due to growing populations of humans that are pushing the animals out of their natural habitat. A lot of animals that are not considered endangered have experienced a huge decline in their numbers, indicating that animals all over the world are being IUCN Red List of Threatened Species. This data was was superimposed in a 22,000 grid of 10,000 km3 quadrats covering continental lands. A species was considered decreasing if their ranges (where that species lives) shrunk over time, or if there was a reduction in the number of species. This approach was also applied to 177 species of land mammals to see how their populations have changed through time.

Results: The scientists found that even in populations of animals that are not considered threatened, the rate of population loss is extremely high. In this study, 32% of the known vertebrate species are decreasing, meaning they have shrunk in population size and the ranges, or land in which they live. In the more detailed data set of 177 mammals, all of them have lost 30% or more of their ranges, and more than 40% of the mammal species have experienced severe population declines.

This map represents the percent of population extinctions in 177 species of mammals. The maps were made by comparing historic ranges of the animals to the current ranges. Cooler colors indicate areas that are experiencing the most severe population extinctions (for example, the east coast of the US, southern Australia, and northern Africa).

Why is this study important? This study uses a large data set of vertebrates to examine patterns of species through time to specifically assess how humans are impacting the ranges and populations of the animals. The current decline of species on Earth isn’t happening slowly; instead, it is happening at an accelerated rate. This study highlights the idea that Earth and all its creatures may be in the Sixth Mass Extinction, and remediation efforts are necessary and need to be enacted now in order to save animal populations.

The Big Picture: Humans are fundamentally changing the Earth and the animals that live on it. Through habitat destruction and expansion of housing and urban areas, to name just a few causes, we are taking habitats away from animals. Combined with climate change, the Earth’s animals are experiencing a biodiversity decline.

Citation: Ceballos, G., Ehrlich, P. R., and Dirzo, R., 2017. Biological annihilation via the ongoing sixth mass extinction signaled by vertebrate population losses and declines. PNAS. DOI: 10.1073/pnas.1704949114

Unusual bird hatchling fossil preserved in amber (Burma)

A mid-Cretaceous enantiornithine (Aves) hatchling preserved in Burmese amber with unusual plumage
Lida Xing, Jingmai K. O’Connor, Ryan C. McKellar, Luis M. Chiappe, Kuowei Tseng, Gang Li, Ming Bai

What data was used? Newly discovered Cretaceous-age (~100-65 million years ago) amber specimens that contain parts of a bird hatchling; rarely found soft tissues of the plumage were also preserved. These specimens were found in Myanmar.

The fossil, preserved in amber (bottom right); CT scan of the fossil (bottom left) and the author’s reconstruction of it (top). You can see the rare fossil feathers in the amber!

Methods: The specimens, encased in amber, were CT scanned using a micro CT scanner. Each preserved piece of the bird skeleton (e.g., neck, foot, etc.) were scanned separately. Researchers then did a 3D reconstruction of the bird, combining all of the scanned pieces.

Results: Researchers found that a number of the bones in this specimen were unfused, which indicates that the bird was very young (bones typically fuse as an organism grows-human babies do this too!). The specimen preserved two types of feathers: downy-type feathers and outer feathers, similar to birds today and to some of the earliest birds in the Jurassic, like Archaeopteryx, the famous bird-dinosaur transitional fossil.

Why is this study important? Feathers and other types of soft tissue are exceedingly rare in the fossil record! Typically, the only things that get preserved are bones, shells, and other hard tissues. Amber is one of the ways that soft tissue can be preserved; when we find soft tissue preserved, it’s certainly a reason to celebrate! This data can shed a lot of light on how organisms looked from millions of years ago. This hatching’s preservation tells us a lot about how feathers in juvenile birds looked from the Cretaceous, and can be compared to the other soft tissue feathers that have been found previously belonging to adult birds. The bones also provide more information on how skeletal changes of birds occurred from juvenile to adult stages.

The big picture: Soft tissue preservation is an incredible opportunity to learn about organisms that lived a very long time ago-other soft tissue fossils have shown us what dinosaur skin looked like, how organs of extinct mammals look, and more. As you can imagine, it’s also rare to find well-preserved juveniles in the fossil record (many groups of fossils don’t have juvenile representatives at all!), so when we do find examples of younger organisms, it’s important to study them to understand how their bodies changed throughout their lifetime.

Citation: Lida, X., O’Connor, J.K., McKellar, R.C., Chiappe, L.M., Li, G., Bai, M., 2017, A mid-Cretaceous enantiornithine (Aves) hatchling preserved in Burmese amber with unusual plumage

The Dinosaur that Went Viral: Looking at the science behind the Facebook posts

An Exceptionally Preserved Three-Dimensional Armored Dinosaur Reveals Insights into Coloration and Cretaceous Predator-Prey Dynamics

Caleb M. Brown, Donald M. Henderson, Jakob Vinther, Ian Fletcher, Ainara Sistiaga, Jorsua Herrera, Roger E. Summons

Summarized by Time Scavengers contributor, Maggie Limbeck

What data were used? The holotype specimen (fossil or other specimen that all others are compared to to determine what it is) of Borealopelta markmitchelli was used for all experiments touched on in this article. Data was also collected from other members of the Ankylosauria (armored, herbivorous dinosaurs with a club on their tail) clade for comparison.

Methods: A phylogenetic analysis (family tree) was completed using this new dino as well as others from the Ankylosauria and Nodosauridae (Ankylosaurs missing the club on their tail) clades to determine where in the dinosaur tree B. markmitchelli belongs. This also provided data for comparison in life habit and some of the unusual features of this particular dinosaur. Additionally, geochemical studies were done on this specimen, including scanning electron microscopy (SEM) and time-of-flight secondary ion mass spectroscopy (TOF-SIMS). Both of these methods were used to get an idea of what the preserved organic material on the specimen was and determine what kinds of fossil melanins (pigments) were present.

Results: The resulting phylogenetic tree from this study does place B. markmitchelli where one would expect it to go within the Ankylosauria tree (within the Nodosauridae clade). The TOF-SIMS experiment showed that there were ions present that indicate benzothiazole and therefore pheomelanin was present. These particular chemicals would indicate that parts of this dinosaur were reddish-brown in color. However, not all parts of the osteoderm (bony skin) and epidermal coverings (scales) show this reddish-brown coloration.

Figure 1. A graphical summary of the paper. We see an image of B. markmitchelli that is exceptionally preserved, the results of the mass spectroscopy experiments that told us that there is countershading (camouflage) caused by the pigment pheomelanin that gave the dinosaur a reddish brown color. This reddish-brown color is a result of strong predation pressure and an attempt to better camouflage themselves.

Why is this study important? This study is important because it highlights how much we can learn from one extremely well preserved individual fossil. It was used in a phylogenetic analysis to determine where it belongs in the dinosaur-scheme of things, images were taken of the skull, and geochemical data was returned to determine the coloration of the skin. From these studies the scientists were able to determine that these dinosaurs used camouflage to help protect them from predators. This is very different from what we see today in predator-prey interactions. Borealopelta markmitchelli was by no means a small dinosaur (~5.5m long and ~1,300kg) and had significant body armor yet it still needed camouflage. Today, large mammals comparable to this size do not need camouflage because even the fiercest predator does not go after grown adults. This new relationship between Cretaceous predator and prey highlights major differences in large predator-prey interactions through time. This specimen will continue to play a major role in research for years to come.

The big picture: There are really two big picture things to take away from this article. The first being that science, and ground breaking science in particular, is always interdisciplinary. These paleontologists relied on geology, biology, ecology, and chemistry (to name a few) to come to their conclusions about B. markmitchelli. This is really important because people always think that science is very isolating and you only work on your own, when in actuality science is accomplished by a team of people who can support you and fill in knowledge gaps. Second, it is important to look into those flashy science articles that pop up on your newfeeds and on Twitter. Those articles are press releases to get you interested in the science that is being done on these fossils or rocks or bacteria. We scientists get excited about our work and want to share it with people-take the time to do so, get excited about nature, and keep reading!

Citation: Brown et al., An Exceptionally Preserved Three-Dimensional Armored Dinosaur Reveals Insights into Coloration and Cretaceous Predator-Prey Dynamics, Current Biology (2017), DOI: 10.1016/j.cub.2017.06.071

Global risk of deadly heat

Global risk of deadly heat

Camilo Mora, Benedicted Dousset, Iain R. Caldwell, Farrah E. Powell, Rollan C. Geronimo, Coral R. Bielecki, Chelsie W. W. Counsell, Bonnie S. Dietrich, Emily T. Johnson, Leo V. Louis, Matthew P. Lucas, Marie M. McKenzie, Alessandra G. Shea, Han Tseng, Thomas W. Giambelluca, Lisa R. Leon, Ed Hawkins, and Clay Trauernicht

Data: This study was conducted by gathering data from previous studies and looking at the number of lethal heat events that have occurred around the world from 1980 to 2014. The study also estimates the percentage of the population that is at risk from increased air temperatures and humidity due to human-induced climate change in the future.

The number of days per year that different areas are exposed to deadly heat and humidity (‘threshold’). The simulations, a-d, are from models into the year 2100. A) historical data from other published studies; B) RCP 2.6 scenario where nearly all emissions are cut; C) RCP 4.5 is a scenario where most emissions are cut; D) RCP 8.5 is the ‘business as usual’ scenario where emissions are not cut at all.

Methods: The authors used data from 911 previous studies to use in their analysis. They collected information on the place and dates of lethal heat events, or extreme heat events that led to human deaths. The number of days per year that surpassed the heat threshold for which humans can live in was assessed for each year (1980-2014). To determine how much of the population may be at risk of heat-related deaths in the future, the scientists used four different CO2 scenarios to model air temperature and humidity to year 2100.

Results: From the previous studies, the scientists found 783 cases of human mortality linked to excess heat from 164 cities in 36 countries. Cases of heat-related deaths were concentrated to mid-latitude regions, with high occurrences in North America and Europe. Temperature and relative humidity of an area were both found to be factors important to identifying regions where climate conditions may become deadly, as these are related to human’s ability to regulate their body temperature. Currently, around 30% of the Earth’s population is exposed to climate conditions that are considered deadly. By the year 2100, this number is projected to increase to 48% under a CO2 scenario where emissions are drastically cut, and 74% under a CO2 scenario of increased emissions.

Why is this study important? This study highlights the health risks posed to humans due to increased heating of the Earth. Several countries and large cities, mostly concentrated at the mid latitude regions and equator, are at most risk.

The big picture: Under all emissions scenarios, whether we cut emissions drastically or keep emitting CO2 at the same rate, an increased percent of the human population will be at risk of heat-related deaths. This study emphasizes the importance of aggressive mitigation to minimize the human population’s exposure to deadly climates linked to human-induced climate change.

Citation: Mora, C., Dousset, B., Caldwell, I. R., et al., 2017. Global risk of deadly heat. Nature Climate Change, 7, 501-506. DOI: 10.1038/nclimate3322

Evolution of the Arch of the Foot

Chimpanzee and human midfoot motion during bipedal walking and the evolution of the longitudinal arch of the foot
Nicholas B. Holowka, Matthew C. O’Neill, Nathan E. Thompson, Brigitte Demes
Summarized by Time Scavengers contributor, Maggie Limbeck

What data were used? The only data that were utilized in this study were five male humans and two male chimpanzees that were recorded while walking. The scientists applied markers on the joints and other key points in the feet of both the humans and chimpanzees based on where they hypothesized to see foot motion in both species. These markers provided the data points that were analyzed in film after the experiment was completed.

Methods: 3D kinematic data (a human or chimpanzee foot in motion) was collected by recording the subjects walking at a self-selected speed for 11 meters. The researchers then selected representative steps for each subject to analyze the motion and utilization in certain regions of the foot. The data was analyzed using the packages ProAnalyst and MATLAB to calculate joint angles and estimate speed of walking. These angles were then used to determine the motion between the markers placed on the foot and understand the differences between human foot motion and chimpanzee foot motion.

Image of both a human and chimpanzee subject while walking. The dots on each foot indicate the markers that the researchers were using for data collection. The percentages on each image indicate the amount of motion in the midfoot that is being utilized during each part of taking a step.

Results: It was found that humans have a much greater range of motion along the sagittal plane (imaginary plane that divides the body into left and right sides) than chimpanzees, but the range of motion along the coronal plane (imaginary plane that divides the body into front and back) were similar in both species. While there were some great differences in motion along other planes the results state that the motion and parts of the foot involved are still activated at some point while walking, they are just activated during different parts of walking in chimpanzees and humans.

Why is this study important? This study is important because it was thought that the arch in human feet evolved to stiffen the foot while walking upright on two legs (bipedally) and that therefore chimpanzees would have a much greater motion in the midfoot than humans would while walking bipedally. This experiment rejects that idea because it was found that humans actually use a significantly greater amount of motion in the midfoot while walking than chimpanzees. This does not however, mean that at all times when walking do humans have more motion in their midfoot. The researchers broke walking into separate phases and during some of those phases the chimpanzees did have much more motion in their feet than humans; but when looking at the step as a whole, humans do have more motion than chimpanzees.

Big picture: The big picture here is that the total difference in range of motion between humans and chimpanzees is pretty small, only 4°. Therefore we can’t rely on using only midfoot joints to explain evolutionary differences between humans and chimpanzees. The authors suggest that looking further into morphology (shape) affects the function of the midfoot throughout motion. Essentially, evolution cannot always be easily explained by differences in bone shape–we must observe the action that the bones might be influencing.

Citation: Holowka, N.B., O’Neill, M.C., Thompson, N.E., Demes, B., 2017, Chimpanzee and human midfoot motion during bipedal walking and the evolution of the longitudinal arch of the foot: Journal of Human Evolution, p. 23-31.