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The Clues Ancient Glaciers Leave Behind on Mars

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Transient post-glacial processes on Mars: Geomorphologic evidence for a paraglacial period

by: Erica R. Jawin, James W. Head, David R. Marchant 

Summarized by: Lisette Melendez

Figure 1: A map of the crater in the midlatitudes on Mars, showing the geologic features that were created due to deglaciation, like gullies and spatulate depressions. These same features can be found in post-glacial environments on Earth!

What data were used? Mars, just like Earth, goes through a cycle of glaciation and deglaciation. The rise and fall of glaciers on Mars is influenced primarily by the planet’s obliquity, or the tilt of its axis. During times of higher obliquity, the planet’s tilt is greater, hence its poles are exposed to more sunlight and the glaciers leave the poles and travel towards the middle of the planet. As the cycle continues and the tilt is lower, the glaciers leave the midlatitudes and migrate towards the poles once again. The period of time where environments are adjusting to deglaciation is known as a paraglacial period, and it comes with a group of identifying features that are well studied here on Earth. This study applies what we’ve learned about the kinds of geologic features that are left behind by glaciers on Earth to the environment on Mars. The area that is left behind by a glacier is known as a glacial deposit. By analyzing images of craters on Mars taken by cameras aboard the Mars Reconnaissance Orbiter, scientists are able to find evidence of paraglacial periods and how long they last on Mars.

Figure 2: A photo of two retreating glaciers in the Antarctic Valley that are leaving behind ridges that are comparable to the ones found on the Martian surface.

Methods:  After choosing a crater in the midlatitudes of Mars, the scientists began breaking down the features found in the images of the crater and mapping out the terrain, as shown in Figure 1. Glaciers leave behind special signatures in the rocks on Earth (e.g., here are some Time Scavengers posts about glacial geology on Earth: glaciers in Connecticut River Valley and glaciers in the Bay of Fundy), and the objective was to identify these same features on Mars. In order to further understand the processes that were occurring in the crater on Mars, analyses of places with the same climate and geologic features on Earth were used! The climate on Mars is arid and freezing, similar to the McMurdo Dry Valleys in Antarctica.

Figure 3: A diagram that shows the process of forming gullies and debris fans (piles of sediment), which can be seen in real-life in the next figure.

Results: Several geologic features that, when found together, are indicative of glaciers migrating away were found in this crater on Mars. Some of these features include ridges becoming increasingly deformed as one looks further downslope, as shown in Figure 2, where the ridges of the glacial deposits in Antarctica are more deformed at the bottom of the picture. Spoon-like holes, called spatulate depressions, were also found on both the Antarctic glacial deposits and the Martian crater, formed by ice weathering away. As glaciers retreat, they often leave behind steep slopes in their wake. These slopes are unstable, and over time, sediment flows downward and builds up on the sides to stabilize the slope, as shown in Figure 3. Gullies, which are a geologic feature formed by the path that the sediment took to travel downward, and the resulting triangular piles of sediment can be found both in the crater on Mars and on Earth, shown side by side in Figure 4.

Why is this study important? This study is important because it increases our understanding of the time frames of climate cycles on Mars, and also highlights the similarities and differences between Mars and Earth. On Earth, paraglacial periods are relatively short, and the features left behind are likely to be eroded away by rainfall, rivers, and vegetation. These features are better preserved on Mars, an extremely cold and dry planet that doesn’t have the same erosive forces.

Figure 4: An example of gullies and debris fans on Mars (left) and on Earth (right).

The big picture:  Understanding the formation of geologic features on Earth is essential to uncovering the geologic history of the rest of our planets. This study showed that several features that form after a glacier migrates away can be found both on Earth and on Mars. The key difference is the time frame: on Earth, the paraglacial period is relatively rapid, while on Mars, it takes place on the scale of millions of years. 

Citation:mJawin, E. R., Head, J. W. & Marchant, D. R. Transient post-glacial processes on Mars: Geomorphologic evidence for a paraglacial period. Icarus 309, 187–206 (2018).

Tracing the Body Plans of Echinoderms through Time

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Evolution and Development at the Origin of a Phylum

by: Bradley Deline, Jeffrey R. Thompson, Nicholas S. Smith, Samuel Zamora, Imran A. Rahman, Sarah L. Sheffield, William I. Ausich, Thomas W. Kammer, and Colin D. Sumrall

Summarized by: Lisette Melendez

What data were used? In this paper, changes in the bodies of early echinoderms (the group that includes marine animals such as starfish and sea urchins!) are tracked in order to understand the trends that separate groups from the rest of the animal kingdom. The main question is: why are all the body plans so different from one another? Figure 1 shows the range of body plans for early echinoderms, but the distinction carries on even today, considering how starfish and sea cucumbers look so different from one another! In order to quantify these changes, the scientists directly studied specimens from various natural history museums, sifted through past echinoderm papers, discussed with experts in organism classification, and consulted the Treatise on Invertebrate Paleontology. Since the scientists were looking specifically at early echinoderms, we are talking about fossils that date back to the Cambrian and Ordovician periods, about 541-444 million years ago! Usually, data from fossils this old is limited because many significant characteristics are worn away with time. However, echinoderms have notable skeletons that retain a great deal of important characteristics, making their skeletons excellent indicators of evolutionary changes through time.

Figure 1: a collection of different early Paleozoic echinoderm body plans. The one featured in (A) is non-radial, (B) is pentaradial attached, (C) is mobile and able to move around freely, and (D) – (F) are pentaradial stalked (hence the stem-like structures).

Methods: Once all the data was gathered, the next step was to find a way to accurately portray the changes of early echinoderm bodies through time. A morphospace, or a representation of every possible shape of echinoderms, was created, as shown in Figure 2. Four major echinoderm body plans were revealed in the graph. Three of the groups had radial symmetry (symmetry around a central part), while one was non-radial. Two of the groups were characterized by stem-like stalks that attached the echinoderm to the sea floor, while another group was mobile and free to move around. While Figure 2 shows the overall body plans of early echinoderms, this graph was further broken down into specific time intervals (each about 20 million years long) in order to study how the body plans changed over time. Figure 3 depicts how different the body plans were from one another throughout time.

Results: By studying the graphs, several important evolutionary trends can be picked out. Take, for example, Figure 3. The Cambrian was when the first major echinoderm body plans appeared, but the Ordovician was really where each body plan became more complex and different from one another, pointing to the Great Ordovician Biodiversification Event. Each body plan became more well-defined over time, and the differences between the various body plans are highlighted by the extinction of the transitional forms that connected one body plan to another. Even as evolution continued to progress, sometimes certain species would “readapt” a characteristic that they lost thousands of millions of years previously, showing how flexible evolution can really be.               

Figure 2: A graph that shows all the different body types of Echinoderms, separated by characteristic differences like mobility and radial symmetry (or lack thereof).

Why is this study important?  This study is important in studying the mechanisms behind the nature of the Cambrian explosion: why do all of these major animal groups start appearing and how have the groups changed over time? This study shows how fluid characteristics are throughout time, with the introduction, removal, and possibly even a re-introduction of characteristics to body plans as time progresses (this is called homoplasy). It highlights the various patterns of body types within Echinodermata and the patterns of gaining or losing characteristics over time, indicating the complexity in studying how animals change over time.

Figure 3: A graph that shows the diversity of echinoderms between the Cambrian and the Ordovician (541 – 444 million years ago).

The big picture: This study helps us fill in some of the gaps in our knowledge about the Cambrian Explosion, a consequential chapter in the history of living creatures, and how animals have evolved since that point. It shows how evolution has changed the bodies of animals within the same group over time and helps us understand how some animals (like sand dollars and brittle stars) can look so different, yet be closely related to one another. 

 Citation: Deline et al., Evolution and Development at the Origin of a Phylum, Current Biology (2020), https://doi.org/10.1016/ j.cub.2020.02.054

The relationship between rodents and Homo floresiensis

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Temporal shifts in the distribution of murine rodent body size classes at Liang Bua (Flores, Indonesia) reveal new insights into the paleoecology of Homo floresiensis and associated fauna

by: E. Grace Veatch, Matthew W. Tocheri, Thomas Sutikna, Kate McGrath, E. Wahyu Saptomo, Jatmiko, and Kristofer M. Helgen.

Summarized by: Kailey McCain

What data were used? Researchers once believed that Homo sapiens (i.e., modern humans) were the only hominid to reach the Indonesian islands. However, in the past few decades anthropologists, archeologists, and paleontologists have discovered an early hominid species’ cultural and skeletal remains, belonging to Homo floresiensis, on the island of Flores. Along with the hominid remains, 257,000 additional vertebrate skeletal elements were identified and 80% of the collected belonged to the murine rodent taxa (i.e., rats). The main rodent genera identified and used in this study varied in body size, which was used as a proxy (i.e., representative) to identify the paleoecology of the environment. The five genera used were: Papagomys, Spelaeomys, Hooijeromys, Komodomys, Paulamys, and Rattus (Figure 1).

Methods: The excavation site for the murine skeletal remains, as well as H. floresiensis, was within the Liang Bua, a limestone cave on Flores Island. The stratigraphy of Liang Bua was divided into sectors based on age, with the oldest being approximately 190-120 ka (thousand years ago) and the youngest sector at less than 3 ka. Once the sites were identified, researchers began excavating the remains by using a method called wet-sieving, which is the process of sediment separation using water to remove certain grain sizes and break apart agglomerates (i.e., a mass of sediment grains).

Once the murine remains were collected, researchers began identifying the different species by using molar and jaw sizes, as well as comparing the skeletal body to size to extant (i.e., living) rodents. In addition to dividing the remains into their different species, they were also further divided by size. The five distinct body size categories are: small (<100 g), medium (100-300 g), large (300-600 g), huge (600-1100 g), and giant (>1100 g).

Figure 1: This image represents how the different murine taxa, Papagomys, Spelaeomys, Hooijeromys, Komodomys, Paulamys, and Rattus, differ in body size and molar size.

Results: The data collected showed that the small and medium sized murines dominated the cave during the first two sectors (190-60 ka) but researchers noted a sharp decline in the medium sized murines during the 60-50 ka age range. This decrease in species can be correlated to the paleoclimate record, which indicated a substantial decrease in available vegetation. As time progressed to the age range 47-12 ka, researchers noticed no significant change in body size. This was a surprise to the researchers due to the geologic record indicating high levels of volcanic activity. The next range, 12-5 ka, exhibited a decrease in overall murine size that can be attributed to the high rainfall and monsoon season recorded for this time period. Finally, the age range 5-3 ka, showed the first increase of medium sized murines which could be correlated to the dispersal of Homo floresiensis and the subsequent opening of habitats, but will need further research to support the claim.

Why is this study important? This study is important because it shows the relationship between the dominant non-human animals and Homo floresiensis within the Liang Bua cave. Additionally, the researchers explored other ecological factors (e.g, weather, resource availability, volcanic activity) and showed how it affects not only the fauna in general, but showed the difference in responses between sizes.

Figure 2: This figure shows two images. Image (a.) shows researchers measuring a large modern cave rat, Papagomys armandvillei. Image (b.) shows a reconstructed image of H. floresiensis carrying a large rat over their shoulder.

The big picture: The researchers set out to determine the ways in which the dominant fauna, second to the hominid species, responded throughout time with the introduction and dispersal Homo floresiensis. While there was a relationship noted between murine size/distribution and hominid involvement, the data also suggested that additional ecological factors may have contributed; therefore, no significant conclusions can be made without additional research regarding the true impact of Homo floresiensis. 

Citation: Veatch, E. G., Tocheri, M. W., Sutikna, T., McGrath, K., Saptomo, E. W., & Helgen, K. M. (2019). Temporal shifts in the distribution of murine rodent body size classes at Liang Bua (Flores, Indonesia) reveal new insights into the paleoecology of Homo floresiensis and associated fauna. Journal of human evolution, 130, 45-60. https://doi.org/10.1016/j.jhevol.2019.02.002

Looking at past phosphorus accumulation in a Florida lake offers new insight on recent cultural nutrient enrichment

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A Holocene Sediment Record of Phosphorus Accumulation in Shallow Lake Harris, Florida (USA) Offers New Perspectives on Recent Cultural Eutrophication

by: William F. Kenney, Mark Brenner, Jason H. Curtis, T. Elliott Arnold, Claire L. Schelske

Summarized by: Mckenna Dyjak

What data were used?: A 5.9 m sediment core was taken in Lake Harris, Florida using a piston corer (a technique used to take sediment samples, similar to how an apple is cored). Lake Harris is a subtropical, shallow, eutrophic body of water (rich with nutrients) located near Orlando, Florida.  

Methods: The 1.2 m sediment core is long enough to provide the complete environmental history of Lake Harris. However, the core must be interpreted first. In order to do so, the core was first dated using lead isotope 210Pb and carbon isotope 14C. The next steps involved using proxy data (preserved physical characteristics of the environment) to determine net primary productivity (the concentration and accumulation rates of organic matter), lake phosphorus enrichment (three forms of phosphorus), groundwater input (concentration and accumulation rates of carbonate material, like limestone), macrophyte abundance (e.g., sponge spicules), and phytoplankton abundance (e.g.,diatoms).

Results: The study found that Lake Harris began to fill with water in the early Holocene (~10,680 calendar years before the present) and transitioned to a wetter climate in the middle Holocene. The transition is indicated by a change in carbonate to organic sediments; a higher amount of organic sediments would suggest an increase in rainfall needed to support the plant life that would become the organic matter. A low sedimentation rate indicates that the lake was experiencing oligotrophication (depletion in nutrients) through the Holocene until around the 1900s. After the 1900s, there were increased sedimentation rates (Figure 1. A, B, D, and E) which indicates cultural eutrophication (increase of nutrients in bodies of water). Phosphates and nitrates from common fertilizers and other human activities (which is why it’s called “cultural eutrophication”) can allow algae (e.g., diatoms) to grow rapidly and reduce the amount of oxygen in the lake. An increased sedimentation rate can be used to determine whether a body of water is in a state of eutrophication, because the amount of phytoplankton (such as diatoms) would increase in accumulation. Total phosphorus accumulation rates can also indicate eutrophication.

Figure 1. Sedimentation rates for (A) bulk sediment, (B) organic matter, (C) CaCO3, (D) total phosphorus, (E) diatom biogenic silica and (F) sponge spicule biogenic silica versus core depth. Near the top of the core we can see a significant increase in A, B, D, E, and F which provide evidence for cultural eutrophication (increased sediment rates).

Why is this study important?: This study shows that, without being disturbed, Lake Harris was prone to becoming depleted in nutrients, the process of oligotrophication. The complete change of course due to human activities (i.e., fertilizer runoff) is more detrimental than was previously considered. This study showed that throughout the environmental history of Lake Harris there was never a sign of natural eutrophication, but rather that of oligotrophication. 

The bigger picture: Cultural eutrophication is a serious problem plaguing many aquatic systems and has serious consequences such as toxic algae blooms, which can have far reaching effects like on the tourism industry in Florida! The extent of damage caused by human activities is shown in this study and can help us understand how lakes responded in the past to the introduction of cultural eutrophication.  

Citation: Kenney WF, Brenner M, Curtis JH, Arnold TE, Schelske CL (2016) A Holocene Sediment Record of Phosphorus Accumulation in Shallow Lake Harris, Florida (USA) Offers New Perspectives on Recent Cultural Eutrophication. PLoS ONE 11(1): e0147331. https://doi.org/10.1371/journal.pone.0147331

Understanding how climate change affects predator-prey relationships in snails and clams

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Climate-mediated changes in predator-prey interactions in the fossil record: a case study using shell-drilling gastropods from the Pleistocene Japan Sea

Tomoki Chiba and Shinichi Sato

Summarized by Baron Hoffmeister

What data were used? This study used a predator-prey analysis of drill holes found on fossil bivalve (clam) shells produced by gastropods (snails) found in the Oga Peninsula off the coast of Japan.

Methods: This study used computer analysis on fossil assemblages of bivalves to determine the location of predatory drill holes and the species of bivalves which indicated whether they are warm water dominant or cold water dominant species. The location of the drill holes on the bivalve shells was also analyzed to determine different predatory gastropods (Figure 1).

Figure 1. These are photographs of two predatory drill holes taken from a microscope. Section A-C is a predatory drill hole located on the center of the shell, and section D-F is a drill hole located on the shell edge. These two different types of predation patterns indicate two separate predatory gastropod species. Image from Chiba and Sato (2016).

Results: This study showed that drilling predation was influenced by the change of sea surface temperatures and sea level due to glacial-interglacial climate cycles. A glacial period occurs due to cool temperatures and glacial advancement, and an interglacial period occurs when glaciers retreat and sea level rises due to warming temperatures. As warm water currents decrease, so does the presence of warm-water predator gastropods. This causes them to shift their range, therefore changing rates of predator and prey interactions. In this study, predation slowed as seawater temperatures decreased and in turn found that this moderated the predation pressure between the gastropods and bivalve prey. This study also found that predator and prey interactions in a shallow-marine ecosystem are likely to weaken with cooling temperatures and strengthen with warming temperatures.

Why is this study important? This study indicates that predator-prey relationships can be used to help interpret changing climates and the implications it has on ecosystems. This study also notes that ocean climate variability has large implications of range shifts which can be used to interpret how organisms respond to changing climate conditions.

The big picture: The information found in this study can be used to help interpret current-day climate change and its influence on predator-prey relationships in relation to the biogeographical distribution of species due to ocean temperatures. This is useful for identifying ecosystems globally.

Citation:

Chiba, T., and Sato, S. I.. (2016). Climate-mediated changes in predator-prey interactions in the fossil record: a case study using shell-drilling gastropods from the Pleistocene Japan Sea. Paleobiology 42(2), 257–268. doi: 10.1017/pab.2015.38

Signs of Injury and Disease in Jurassic Marine Reptiles

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Palaeoepidemiology in extinct vertebrate populations: factors influencing skeletal health in Jurassic marine reptiles

Judith M. Pardo-Pérez, Benjamin Kear, and Erin E. Maxwell

Summarized by: Kailey McCain

What data were used? Researchers wanted to create a baseline for measuring overall health of large marine animals in the Jurassic period. Given the prevalence of Ichthyosauria, a large extinct marine reptile, researchers chose to survey five different species/taxa (i.e., biological classification of organisms) that lived at different ocean depths and varied in size: Hauffiopteryx, Stenopterygius, Suevoleviathan, Eurhinosaurus, and Temnodontosaurus.

A total 236 specimens were collected at a Lagerstätte deposit in Germany, which is a site with exceptional (in quantity or quality) fossil preservation.

Figure 1: This image represents four examples of the skeletal pathologies found by researchers. (a) shows stiffness in the femur and fibula (limb bones). (b) shows stiffness in the spinal column. (c) shows a fracture in the gastralium, which provided support in the abdomen. (d) shows a fracture in the rib cage.

Methods: The 236 specimens were classified by species, and then further classified by age range (i.e., juvenile, young adult, adult). Researchers began studying the fossils for signs of trauma that could have resulted from injury or skeletal diseases (pathologies). Due to the large availability of the Stenopterygius specimens, researchers dated and grouped them into three categories regarding the Toarcian Oceanic Anoxic Event (T-OAE). This was a time in the Jurassic Period when the oxygen levels were depleted and toxic greenhouse gases (e.g., carbon dioxide and hydrogen sulfide) became the major component of the atmosphere; the specimens were grouped as before T-OAE, during  T-OAE, and after T-OAE. The purpose behind comparing pathological data to the T-OAE is to determine if the depletion of oxygen had any significant effect on marine health.

All of the data was inputted into a statistical software, R, to determine any significant correlations and variables. 

Results: The data collected showed that trauma associated with healing was the most common pathology recorded; however, there was not a skeletal region significantly affected more than the others. These commonalities were shared by all five taxa of ichthyosaurs . Additionally, when comparing the overall size of the specimens and percentage of pathologies found, it was determined that the large species were approximately 2.4 times more likely to show signs of trauma and disease. This correlation was also found to be true when looking at the developmental data collected for Stenopteryguis; it was concluded that the adults were 4 times more likely to have signs of disease or trauma than the juvenile specimens.Regarding the data collected for the Toarcian Oceanic Anoxic Event , researchers could not find any significant data that could correlate an increase in pathologies due to the depletion of oxygen.

Figure 2: This image shows a fully preserved fossilized ichthyosaur, Stenopterygius .
https://www.nationalgeographic.com/science/2018/12/incredible-jurassic-ichthyosaur-fossil-preserves-skin-blubber/

Why is this study important? This study showed the differences in skeletal pathologies present in a diverse set of marine reptiles. By differing in size, age, time, and ocean depth, researchers were able to obtain an overall survey of health and easily compare the pathology data to other ecological conditions (e.g., climate change).

The big picture: The research collected in this study provided a baseline for variables that affected the skeletal health of Jurassic marine reptiles. The data supporting the correlations between size and age range of different taxa within the extinct Ichthyosauria can be compared to other extant (i.e., living) reptiles to provide an estimation and a possible explanation for the prevalence of skeletal pathologies.

Citation: Palaeoepidemiology in extinct vertebrate populations: factors influencing skeletal health in Jurassic marine reptiles. (2019). Royal Society Open Science, 6(7). https://doi.org/10.1098/rsos.190264

Behind the Storm: How Climate Change Affects Women’s Empowerment in Africa and Asia

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A Qualitative Comparative Analysis of Women’s Agency and Adaptive Capacity in Climate Change Hotspots in Asia and Africa

by: Nitya Rao, Arabinda Mishra, Anjal Prakash, Chandni Singh, Ayesha Qaisrani, Prathigna Poonacha, Katharine Vincent, and Claire Bedelian

Summarized by: Lisette Melendez

What data were used? This study focused on the lives of 25 women from geographically different areas in Africa and Asia, including deserts, mountains, and deltas. Even though their cultures and livelihoods differed, they were connected by one phenomenon: climate change. Climate change is something that affects humanity as a whole, but the most severe impact will be felt by our vulnerable communities. As summers grow hotter and droughts increase, those whose livelihoods depend on natural resources will face extreme adversity in the coming years.

Figure 1: A map of all the areas that were surveyed in this study.

Methods: The focal point of the study was to investigate how a woman’s agency – or ability to make meaningful and strategic decisions – was impacted by her surroundings. During field research, each woman was interviewed and their livelihood, exposure to environmental risks (like cyclones, flooding, and storm surges), and societal standing were charted. Then, conditions like material possessions, supportive legal systems, and environmental stress were analyzed in each situation to measure the impact each had on the given woman’s life.

Results: With climate change leading to inconsistent rain and extreme temperatures, land becomes infertile and inadequate for farming. Men often migrate away in search of better job opportunities, and while this presents as a source of empowerment for women, with the chance of increasing their involvement in managing money, the research shows it was actually a burden. One young woman noted, ‘Men can easily migrate for work whereas we have to stay here (at home) to take care of the family’. The women were often left alone to provide food for their children and maintain the crops and pay the bills. Even in states with relief programs for floods and droughts, women were often excluded from receiving aid – reinforcing cultural norms that disadvantage women globally. The same trend can be seen in the United States right at this very moment, with up to 90% of women and minority business owners being excluded from the Paycheck Protection Program.

Environmental stress overshadowed the benefits women received from becoming a greater part in household decisions and in the workforce. Why? Because climate change has destructive consequences for the environment in which these women base their lives on. The struggle to simply survive in barren fields forces women to work harder, in poorer conditions, and for lower wages.

Figure 2: The United Nations’ Sustainable Development Goals

Why is this study important? This study provides vital information for governments to implement effective social programs for their citizens. It advances conversations about gender equality on the international stage and urges leaders to commit to gender equality when drafting important documents like the United Nations’ Sustainable Development Goals and the Sendai Framework for Disaster Risk Reduction.  

 The big picture: The negative environmental impacts of human-driven climate change are now inevitable: global temperatures will continue to rise, droughts will become more prevalent, and storms will intensify. It is important, now more than ever, to ensure that countries have the necessary social programs that can effectively help people sustainably adapt to the changing environment. Resources and adaptation strategies must be made available to the communities that are most vulnerable to fluctuating circumstances. 

Citation: Rao, N., Mishra, A., Prakash, A. et al. A qualitative comparative analysis of women’s agency and adaptive capacity in climate change hotspots in Asia and Africa. Nat. Clim. Chang. 9, 964–971 (2019). https://doi.org/10.1038/s41558-019-0638-y

Climatic variations over the millennia analyzed for predicting future climatic variability

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Little Ice Age climatic erraticism as an analogue for future enhanced hydroclimatic variability across the American Southwest

by: Julie Loisel, Glen M. MacDonald, Marcus J. Thomson

Summarized by: Baron Hoffmeister

What data were used? This study used climate data from climate proxy databases and dendrochronology  along with computer software for modeling climate patterns  

Methods: This study used climate proxy data in conjunction with computer modeling and simulation software to determine hydroclimatic variability (i.e. the change in water conditions) in the North American Southwest.

Results: This study found that in the North American southwest is prone to variable climate conditions such as drought, as well as rapid snowmelt and severe rainstorms that can lead to flooding. Hydroclimatic variability in the southwest has not remained constant over the past one thousand years. In fact, there was high climate variability in the North American southwest during the Medieval Climate Anomaly (MCA; i.e. a period of warm climate that lasted from 950 c. to 1250) and the Little Ice Age (i.e. a period of cooling right after the MCA lasting until about 1850). Results show that the Little Ice Age had a higher amount of variability than the Medieval Climate Anomaly (see Figure 1). This was confirmed using climate data from tree ring growth analysis (i.e. the space between rings indicates the amount of growth) obtained by the North American Drought Atlas, a network of climate data points covering North America (figure 2), as well as climate proxy data from the El Junco diatom index from the Galapagos Islands. A diatom is a single-celled alga with cell walls made of silica. The oxygen used to make the silica is preserved in their shells and can be helpful climate proxy data.

Figure 1. This is a time series that displays annual climate variations based on the Palmer Drought Severity Index (i.e. climate data regarding precipitation and temperature). There is greater variability in the Little Ice age than the Medieval Climate Anomaly, and this can be seen by the bar graph at the bottom of the figure. This bar graph indicates the number of years where variability is above the 90th percentile.

This study also compared climate proxy records from fossil-coral oxygen isotopic records from Palmyra island in the tropical Pacific that recorded El Niño Southern oscillation patterns. El Niño Southern Oscillation is a weather pattern that has irregular periods of variation in wind and sea surface temperatures over the tropical eastern Pacific. Records of these weather patterns can be found in assemblages of certain coral fossils which serve as indicators for sea surface temperatures from the past. These were all analyzed and compared with the El Junco diatom index, and tree ring growth data using computer software. The researchers found a correlation between the El Niño Southern Oscillatory system and drought amplitude in the North American southwest increasing hydroclimatic variability. Also, with recent weather patterns, the computer simulations suggest that a ‘warm Little Ice Age’ scenario with high hydroclimatic variability accompanied by periods of warm and dry conditions is likely to occur sometime during the 21st century. 

Figure 2. The black border is the southwestern portion of North America being considered for this study. The black squares are climate data points provided by the North American Drought Atlas.

Why is this study important? This study shows how past climate change can help us understand how climate can change in the future and what the effects of that might be. In the North American southwest, hydroclimatic variability can lead to floods and drought impairing proper land management. Without experiments like this, climate change and its global effects cannot be understood. The results produced from this study can be used as a model for developing other climate reconstruction models.  

The big picture: This study explores the potential for climate variability modeling using historical climatic data as a reliable indicator for future climate predictions. It is important to be able to understand these historical climate events and weather patterns along with their effects on environments. Successfully being able to do this can lead to well-rounded land and water resource management in the face of climate change. 

Citation: Loisel, J., Macdonald, G. M., & Thomson, M. J. (2017). Little Ice Age climatic erraticism as an analogue for future enhanced hydroclimatic variability across the American Southwest. Plos One, 12(10). doi: 10.1371/journal.pone.0186282

The environmental consequences of potential agricultural activity on land that will become suitable for crops due to climate-change

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The environmental consequences of climate-driven agricultural frontiers

L. Hannah, P. R. Roehrdanz, K. C. KB, E. D. Fraser, C. I. Donatti, L. Saenz, T. M. Wright, R. J. Hijmans, M. Mulligan, A. Berg, A. van Soesbergen

Summarized by Mckenna Dyjak

What data were used?: Climate-driven agricultural frontiers are areas of land that currently do not support the cultivation of crops but will transition into crop-yielding land due to climate change. The frontiers were identified using seventeen global climate-models (mathematical representations of atmosphere, land surface, ocean, and sea ice used to project future climates) for Representative Concentration Pathways 4.5 and 8.5 (RCPs, greenhouse gas concentration trajectory). The climates in which twelve globally important crops (corn, sugar, wheat soy, etc.) can grow were determined by using three modeling methods: Ecocrop (model of crop suitability based on known ranges of optimal temperature and precipitation), Maxent (used in determining species distribution under climate change) and the frequency of daily critical minimum and maximum temperatures provided by the NOAA Earth System Research Laboratory Twentieth Century Reanalysis Version 2. Water quality impacts, soil organic carbon impacts (consequences of the release of organic carbon preserved in soil), as well as biodiversity impacts (variety of life in an ecosystem) were data used in this study to determine the outcome of developing the frontiers. 

Methods: The climate-driven agricultural frontiers were found by aligning the preferred climate of crops with the predicted climate determined by the RCPs. The water quality impact was analyzed by using a hydrological model to determine the fraction of water that would be contaminated by the agriculture on the frontiers. Soil organic carbon impacts were determined by using a global dataset that estimates the amount of soil organic carbon present at the top 100cm (soil can store some of the organic carbon that is cycled throughout the earth). The biodiversity impacts were assessed by compiling biodiversity hotspots, endemic (found only in a certain area) bird areas, and Key Biodiversity Areas and comparing them to the agricultural frontiers to find any overlap.

Results: The climate-driven agricultural frontiers were found to cover 10.3-24.1 million km2 of Earth’s surface; the areas can be seen in Figure 1. The models project that the largest portion of frontiers will be in the boreal regions of the Northern Hemisphere (e.g., places where coniferous trees- like pine trees- thrive) and mountainous areas across the world. In these areas, it was found that potato, corn, and wheat are the crops that will make the biggest contribution to the potential agriculture lands. 

Figure 1. These are the predicted global climate-driven agricultural frontiers for RCP8.5 2060-2080 (scenario of future climate if society does not make efforts to cut greenhouse-gas emissions). The areas in blue are future frontiers that will transition from no current ability to support crops to the ability to support one or more crops. The areas in red are uncultivated areas that will transition to support multiple crops.

The release of carbon from the soils in the agricultural frontiers was predicted to be about 177 gigatons of carbon after 5 years of plowing took place on the untilled land (land not cultivated for crops). There is so much carbon stored in the topsoil layer of these frontiers that the 25-40% estimated release is equivalent to around 30 years of current US carbon emissions. These numbers do not include the release of carbon that will occur in the high-latitude soils due to warming alone. When analyzing the biodiversity impacts it was found that 56% of biodiversity hotspots, 22% of Endemic Bird Areas (EBAs), and 13% of Key Biodiversity Areas (KBAs) intersect with the agricultural frontiers. The fact that suitable climates for species will change with warming as well was taken into account (both crop and species suitability moves upslope). Water quality will be negatively affected by the biocide runoff in these frontiers and will affect 900 million to 1.6 billion people, as well as ecosystem health. 

Why is this study important?: Russia is already discussing using the warming land to their advantage for developing agriculture and it is likely that Canada will as well. This study outlines the detrimental outcomes of cultivating these lands and urges for international policies for sustainable development of the frontiers. Due to climate change and unsustainable farming practices current farmland is becoming unusable. With a predicted increase in need for food due to a growing population, as well as unusable farmland, there will be a push for developing new lands; however, it is important to know the potential risks and how to mitigate them.

The bigger picture: With climate change and population growth occurring side by side it is important to know how to handle them in the worst-case scenarios and what measures will need to be taken to do so. It is also important to note that food insecurity is not usually linked to food production but rather to socio-economic disconnects such as food deserts (neighborhoods without healthy food sources). 

Citation: Hannah L., Roehrdanz P. R., K. C. K. B. , Fraser, E. D. G., Donatti, C. I. , Saenz, L., Wright, T. M., Hijmans, R. J., Mulligan, M., Berg, A., and van Soesbergen, A. (2020) The environmental consequences of climate-driven agricultural frontiers. PLoS ONE 15(2): e0228305. https://doi.org/10.1371/journal.pone.0228305

Using Cliffs on Earth to Understand Water Flow on Ancient Mars

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Prolonged Fluvial Activity From Channel-Fan Systems on Mars

by: Gaia Stucky de Quay, Edwin S. Kite, and David P. Mayer 

Summarized by: Lisette Melendez

What data were used? In geology, there’s a basic pillar called “The Principle of Uniformitarianism”. It suggests that geologic processes almost always occur in the same manner and intensity now as they did in the past – which is why geologists can look at the rock record to learn more about Earth’s future. In the same vein, many geologic processes that occur on Earth, like landslides, volcanoes, and erosions, can be used to study the same processes on different planets!

This study focused on analyzing pictures of alluvial fans (finger-like deposits that are usually created when running water in arid or semi-arid (e.g., deserts) flows downhill onto a flat surface, as shown in Figure 1) on Mars taken by the Context Camera (CTX) on the Mars Reconnaissance Orbiter (MRO). The scientists also compared Martian alluvial fans to the ones found here on Earth using elevation data collected by the NASA Shuttle Radar Topography Mission. These alluvial fans usually mark the end of a water channel, so they can be used to study ancient water deposits on Mars.       

Figure 1: An example of an alluvial fan on the surface of Mars, taken by the Mars Reconnaissance Orbiter.

Methods: To study the channels of Mars, the CTX images were converted into digital elevation models, so information like width, slope, and height could be gathered from the data. The valleys on Mars were also measured for how closely they resembled a V-shape. Valleys shaped by rivers have a V-shape, while valleys shaped by other features, like glaciers, tend to have a U-shape.

After gathering all this data, the scientists desired to make an inference about the sediment on Mars, which is too small to be picked up by the camera. So, they turned to places on Earth that had alluvial fans that were very similar to the ones being studied on Mars: the Serra Geral in Brazil, the Great Escarpment in western South Africa, and the Western Ghats in India. These places were ideal parallels for the Martian surface because there’s little to no active tectonic plate movement in the area and the rocks are very well preserved over a long period of geologic time. The big difference is that instead of being placed along mountainsides or plateaus, the slopes that are being studied on Mars are usually along crater rims. 

Results: The channels studied on Mars were found to be less concave (curved inwards) and have very steep slopes, indicating a dry environment. The data on concavity and erodibility (likeliness to erode away) on the Martian alluvial fans was most similar to the data found on the South African slopes, which reinforces the idea that the environment was similarly hot and dry.

Figure 2: The cliffs of Earth (Brazil, South Africa, and India) used to study the sediment on the Martian surface.

Why is this study important? This study is another piece of evidence behind the idea that Mars was once full of water, before it underwent serious climate change. Understanding the history of water on Mars is crucial to understanding what conditions are necessary for life to evolve (which can help paleontologists learn about the first life on Earth, too!). It’s also interesting to note how we can learn more about planets that are millions of miles away by looking right here on Earth!

 The big picture: More than a billion years ago, water used to run freely on the surface of Mars, creating channels and alluvial fans. Scientists use images of the geologic features that remained after water was no longer on the Martian surface to learn more about the history of the Red Planet and the potential implications for human exploration. Learning more about the surface and climate of Mars is necessary for understanding the hazards and potential resources that would be encountered on a crewed mission to Mars.

Citation: Stucky de Quay, G., Kite, E. S., & Mayer, D. P. ( 2019). Prolonged fluvial activity from channel‐fan systems on Mars. Journal of Geophysical Research: Planets, 124, 3119– 3139.  https://doi.org/10.1029/2019JE006167