Posts by Anna LoPresti

Environmental History of Argentina’s Oldest National Park Unveiled

Posted by on Sep 6, 2016 in All Posts, Featured Posts, Science | 0 comments

Environmental History of Argentina’s Oldest National Park Unveiled

Spread the News:ShareA new study has shed light on the environmental history of Nahuel Huapi, the oldest national park in Argentina. The mountainous glacial region in northern Patagonia is vast, spanning two million acres, yet it has remained relatively unstudied, and little of its ecological history is understood. A study published on August 10 in ScienceDirect has revealed a window into the complex history of glacial Lake Perito Moreno Oeste in Nahuel Huapi, using lake sediments to look back through time. The research team, led by the Argentinian scientist Natalia Williams, investigated the glacial lake’s history by digging deep into the lake’s sediment. Williams and her team hoped to better understand the environmental factors like temperature and human activities influencing the lake’s ecology over the past 700 years, and had the help of a small aquatic species known as Chironomidae. Also known as midges, Chironomidae are a type of insect found on every continent including Antarctica. Across the globe, Chironomidae are abundant and can be used to understand the health and condition of water ecosystems. Unlike other species of their size, Chironomidae leave well-defined remains in lake sediments that allow researchers to study them like fossils. There are over 4,000 distinct Chironomidae species, which thrive in different environment conditions–some prefer warmer water while others prefer cold. By examining the number and species of past Chironomidae, the researchers can understand the health, composition, and temperature of the ecosystem through time. The team collected the proxy data by dropping a 43 cm-long hollow pipe, known as an LL, into the bottom of the lake at Llao-Llao Bay—the deepest point of the lake at 20 meters. When the core was dropped, it filled with sediment and trapped preserved organisms. When the pipe was pulled to shore, it contained the layers of sediment which had built up over time, providing a chronological history of the lake. The researchers were then able to analyze the sediment through photographs, chemical tests, and observations of the sediment and individual midges once they cut the pipe in half. Within the 43 cm-long core, a total of 1594 Chironomidae head remains were identified, and their depth within the core informed the researchers about the time of the deposition, with earlier organisms found deeper in the core. There were higher numbers of warm water species found at the surface layers of the core, representing the more recent history around 1900.  Their high abundance within the core corresponded to a period of time with higher temperatures and increasing human presence in Patagonia. The first buildings within the national park near Lake Perito Moreno were constructed in 1937, and the isolated glacier lake quickly became influenced by pollution, rising temperatures, the introduction of fish species, and the construction of roads. Though the lake was free of human influence until the beginning of the 1900s, the ecology of the lake quickly changed in response to human presence in the park. As roads were built and new species were introduced, the lake’s oxygen levels increased beyond healthy levels and allowed the explosion of the Chironomidae population. When the sediment core showed high levels of the species’ remains, the researchers determined that the lake was less healthy than the period prior to human influence, experiencing an ecological imbalance that prevented other aquatic species from thriving. In order to understand the full extent of human impacts on glacial environments, the history of a region must be taken into account. While it is not possible to go back in time to observe the past, species like those within the Chrionomidae give scientists the chance understand history more deeply.   Spread the...

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As Temperatures Rise, Poplars Replace Alaskan Tundra

Posted by on Aug 30, 2016 in All Posts, Featured Posts, Science | 0 comments

As Temperatures Rise, Poplars Replace Alaskan Tundra

Spread the News:ShareIn Alaska’s Denali National Park, summer temperatures have risen 2 degrees Celsius over the past century, with the majority of change occurring since the 1970s. The glaciers that cover 1 million square miles of the park are melting rapidly, exposing bare earth where there once was ice. An Ecosphere study, published July 19, finds that the rising temperatures impacting the glaciers are also affecting the plant communities that grow in newly exposed areas, fundamentally altering the Alaskan landscape and ecosystems. The research team, led by Carl Roland and Sarah Stehn, investigated how the Alaskan landscape near Denali’s Muldrow Glacier changed over time by recreating a study conducted 54 years ago by Leslie Viereck. In 1966, prior to the 2 degree temperature rise, Viereck set out to determine the plant succession in the area. Succession is the process of an ecosystem evolving over time. In mountain regions, it can occur when a glacier retreats or a river forms an outwash plain, and a new community of vegetation can grow. Viereck studied the outwash plain of the McKinley River, which flows west out of Muldrow Glacier, and examined areas ranging from 1 to roughly 5,000 years old. Based on his observations, he determined that the bare rocky plain would transition into a meadow, followed by small shrubs and eventually becoming a tundra ecosystem, with thick moss and a low canopy of shrubs. Half a century later, Roland, Stehn and their colleagues were able to replicate Viereck’s study to see if the temperature change has impacted the successional path laid out by their predecessor. Using a series of photographs, GPS, field notes and re-measured areas of land, the team found surprisingly different results. The newly exposed areas were not transitioning into meadows, but instead covered in balsam poplar trees. The new Alaskan landscape showed signs of succeeding into a forest rather than tundra—representing a completely different biome change. According to the study, the temperature rise fundamentally altered the climatic conditions of the ecosystem, and as time passes, the differences become increasingly larger. Like an archer shooting an arrow hundreds of meters away, even a small shift in the starting point can change the trajectory completely, and yield a very different outcome in the ecosystem structure and function. The poplars began to grow in the early succession landscape because they thrive in the warming climate, and require warmer soils to grow. Once the trees were established, they had the competitive advantage over other plant species—they produce seeds early and abundantly, and are able to thrive in bare soil when other species are not yet present. Once the trees begin to grow, they alter the landscape by blocking the sun from smaller plants, and allowing a different range of species to thrive. Both plants and animals that prefer woodland instead of tundra move to these newly formed forests. The trees also block the wind, allowing snow to build up where it previously would have been blown away. The thick layer of snow prevents permafrost from forming, keeping the soils warm. This one species, through a series of chain events, is able to colonize the area and alter both the species and climate of the region. While the newer areas of exposed land showed a dramatic shift in the projected succession, the older, more established areas of the landscape followed the path as predicted by Viereck. The areas located farther from the river and the end of the glacier plain had begun to grow before the temperature increase. Once the ecosystem had begun to develop, it is much more difficult to change its course. While poplars...

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East African Glaciers at Risk from “Global Drying”

Posted by on Aug 23, 2016 in All Posts, Featured Posts, Science | 3 comments

East African Glaciers at Risk from “Global Drying”

Spread the News:ShareIn the tropical climate of East Africa, glaciers are an unexpected, yet vitally important part of the ecosystem. Since 1900, African glaciers have lost a staggering 80 percent of their surface area, contributing to regional water shortages. While rising temperatures may seem like an obvious cause of global glacier retreat in many regions, the glaciers of east Africa are a unique exception. A study published in Cryosphere earlier this year has found that the largest glacier on Mount Kenya, the Lewis Glacier, is melting because of decreasing atmospheric moisture rather than increasing temperatures. African glaciers have all but disappeared, except for three locations in East Africa: Mount Kilimanjaro in Tanzania, Mount Kenya in Kenya, and the Rwenzori Range in Uganda. Scientists have been studying the few remaining African glaciers in hopes of preserving what is left of the rapidly melting ice. While headway had been made in understanding the causes of melting on Kilimanjaro, the melting on Mount Kenya, Africa’s second tallest mountain, has remained a mystery until now. The complex climatic features of Mount Kenya, combined with the lack of observational data, has made it difficult to pinpoint an exact cause of Lewis Glacier’s retreat. Lindsey Nicholson, a researcher at the Institute of Atmospheric and Cryospheric Sciences, led a study in 2013 that concluded a combination of causes was responsible for the melt, rather than one factor in particular. Building on  her previous work, the team, led by University of Graz’s Rainer Prinz and Lindsey Nicholson, set out to collect the data they needed to gain a more accurate understanding of why Lewis Glacier was melting. They installed an automatic weather station on the glacier at an elevation of 4,828 meters, and collected 773 days of data over the course of two-and-a-half years. In conjunction with the data from the weather station, the team used a model to predict how much Lewis Glacier would melt under a range of different scenarios. By manipulating variables, including precipitation, air temperature, air pressure, and wind speed, in the model, the team was able to see which factors played the biggest role in glacier melt. The team found that moisture had the biggest impact on Lewis Glacier’s surface area, rather than air temperature or a combination of other climatic factors. Despite differences in location and elevation, the glaciers of Mount Kenya and Kilimanjaro are melting for the same reason: East Africa is getting progressively drier, and the lack of water is impacting much more than just the glaciers. The glaciers on the peak of Kilimanjaro lie significantly above the regional freezing point—year round, the peak is cold enough to maintain its ice levels, even as surface temperatures in East Africa have steadily increased. Yet, Kilimanjaro’s glaciers continue to retreat and are projected to disappear completely by 2020. Temperature changes fail to explain the severity of the mountain’s glacier retreat. Observational studies have showed that Kilimanjaro is receiving less cloud cover that leads to increased radiation from the sun, and less precipitation, causing infrequent snowfall. The IPCC has projected a 10% decrease in rainfall during the already dry season from June through August, amplifying the impacts of regional dryness and drought. The impact of a drying climate has greatly impacted Kilimanjaro, and caused its glaciers to retreat from sublimation–a process by which the ice changes directly into water vapor rather than melting into water. The theory that moisture is the main factor impacting glacier melt on Kilimanjaro has, up until now, been assumed to be a product of the mountain’s height and not generalizable to all East African glaciers. Prinz and...

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Photo Friday: The Glaciers of Denali National Park

Posted by on Aug 12, 2016 in All Posts, Featured Posts, Images | 0 comments

Photo Friday: The Glaciers of Denali National Park

Spread the News:ShareDenali National Park spans a vast six million acres in central Alaska, and contains the tallest mountain on the continent that gives the park its namesake: Denali, formerly known as Mount McKinley. The summit reaches over 20,000 feet above sea level, and is one of the most isolated mountain peaks in the world—following only Mount Everest and Aconcagua. Glaciers cover an incredible one million acres of the park, making up one-sixth of the total land area. The park contains hundred of glaciers, but the largest flow from the peak of Denali. Kahiltna Glacier is the not only the longest glacier in the park, but at 44 miles it is the longest glacier in the entire Alaskan Range. Most Denali mountain climbing expeditions start on Kahiltna glacier at Mount McKinley basecamp–or, as its called by climbers, “Kahiltna International Airport.” In addition to offering mountain climbing, Denali is the only U.S National Park with a working kennel. Sled dogs are used throughout the park to reach isolated locations within the wilderness area, and park visitors also have the chance to mush for themselves.   The park is also home to the world’s deepest glacier, the Great Gorge of the Ruth Glacier. The ice is a staggering 3700 feet deep, and is tucked between 4000 foot tall walls of the gorge.   Spread the...

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Ice loss surpasses poaching as largest threat to Barents Sea polar bear

Posted by on Aug 10, 2016 in All Posts, Featured Posts, Science | 0 comments

Ice loss surpasses poaching as largest threat to Barents Sea polar bear

Spread the News:SharePrior to the 1970s, hunting decimated polar bear populations across the Arctic. The international community has made strides in protecting the iconic species from over-harvesting through conservation agreements, which have helped the species start to recover. However, a review paper published in Polar Research in July suggests that the road to recovery is far from over, as ice loss now replaces poaching as the most pressing threat to polar bear survival in the Barents Sea area, north of Norway and Russia. The paper, written by Magnus Anderson and Jon Aars, of the Norwegian Polar Institute, comprehensively covers the history of polar bear population changes over the course of 100 years. By examining historical documents and current scientific studies, the authors find that ice loss, in conjunction with human encroachment on habitat and pollution, have replaced hunting as the largest threat to polar bear populations in the Barents Sea area. Somewhere between 100 and 900 polar bears were poached each year between 1870 to 1970 in Greenland and the Barents Sea region. Arctic countries then came together to protect the species as the bears were pushed toward the brink of extinction. In 1973, the Agreement on the Conservation of Polar Bears was facilitated by the International Union for Conservation of Nature and signed by five countries, marking an important step in the conservation of the polar bear and Arctic ecosystem. With the additional support of Russia’s and Norway’s polar bear hunting bans, enacted in 1956 and 1973, respectively, the Barents Sea polar bear’s outlook became more promising. In Svalbard, a glacier-rich archipelago north of the Norwegian mainland, polar bear populations doubled in the decade following the conservation agreement. There were approximately 2,000 bears in the region as of 1980. While population recovery occurred, it happened slower than anticipated by the scientific community. The Intergovernmental Panel on Climate Change mentioned the impacts of climate change on sea-ice cover for the first time in its third assessment in 2001. The inclusion of ice loss in the report shed light on a potential new threat to polar bear populations, which depend on the Arctic ice for their way of life. It also offered an explanation for the slow recovery of the species following the Russian and Norwegian poaching bans. According to current assessments, the polar bear habitat in the Barents Sea will substantially decrease over the next few decades due to ice loss and glacier retreat, as a consequence of anthropogenic climate change. Polar bear populations are expected to decline accordingly. The Polar Research study states that the main reason for the loss of polar bear populations will be the loss of an ice “platform” needed to hunt for prey — ringed, bearded, and harp seals. As the ice melts, polar bears lose their hunting grounds and must travel greater distances under more treacherous conditions in order to find food. Anderson and Aars cite prior studies conducted by Carla Freitas, Ian Stirling, and others which have tracked trends in polar bear movement with GPS collars and have found that the thickness and persistence of ice significantly affects the location of polar bears and their hunting grounds. In addition to impacting the species’ hunting ability, ice is critical for breeding, traveling, and denning. A loss of  habitat means fewer travel routes for males to find females during the breeding season and a drop in breeding rates across the Arctic. According to the authors’ research, when females have to give birth and raise their cubs, they are hard-pressed to find suitable denning and birthing areas. In the fall, the ice and snow begins...

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