The University of Southampton

Tag: Tundra

Turmoil in the Tundra: the Cold Hard Truth

Posted on by Nikol Raykova

A harsh, cold land with no tree cover, temperatures averaging between -12 to -6 degrees Celsius, and enveloped in snow for the majority of the year (National Geographic, 2017).

Until the brief summer months bring warmth and plains become decorated with swathes of wildflowers. This is the tundra biome.

 

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                                        Figure 1: Arctic animals

 

A home to many endearing (and endangered) animals like the Arctic fox, snowy owl, lemmings and grey-wolves (Figure 1) (National Geographic, 2017). But why should we care about some cold desolate place? The answer is simple yet complicated.

It comes down to the ever looming climate change disaster. The Arctic tundra has been recognised as one of the most vulnerable biomes to environmental change. Permafrost (permanently frozen ground) covers much of the tundra, with the top 30cm or so of it melting and refreezing with the changing seasons (NOAA, 2017). However, in the last few decades increasing global temperatures, and human developments have lead to more melting. This can have a negative effect on the ecosystem as the more permafrost that’s melted, along with the later arrival of the autumn freeze time means that shrubs and other vegetation, that couldn’t take root before, can now grow, potentially altering the habitat (Heijmans et al 2016).

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Figure 2. Different types of interactions within an Arctic tundra ecosystem. Solid lines = consumption between predator and prey between trophic levels (different parts of the food web Dotted lines = interaction between species in the same trophic level (same part of the food web) (Ims and Fuglei, 2005).

 

Northward expansion of Low Arctic trees and shrubs has been seen due to the warmer temperatures and longer growing seasons. This has other ecological consequences, like change in the biodiversity of an area if new species are introduced (Post et al., 2009). Overall ecosystem structure change has been recorded in multiple studies, including interaction between animal species (Hobbie et al 2017).

Although they may be cute and fluffy Arctic foxes are one of the key species within Arctic tundra ecosystems because they are a top predator, meaning they help control herbivore populations (Figure 2). It’s been seen that where abandoned Arctic fox dens are found, the productivity of that area (i.e. plant growth, number of insect and herbivores etc.) has increased (Killengreen et al., 2007).

A study by Ims and Fuglei, (2005) has shown that lemmings are also key players in the Arctic tundra. These rodents are a key prey species for a number of predators that rely on certain densities of lemming populations to allow them to reproduce, as they need sufficient amount of food. Lemmings breed during the winter season and undergo growth under the snow, leading to a peak in population density in spring. This means that with predicted warmer winters (hence less snow, and more rain) lemming peak times are very likely to alter, with population peaks happening during autumn (Putkonen and Roe, 2003). A change in the number of prey available, will impact predator numbers. Arctic fox and snowy owl numbers are likely to decrease as they will have lower reproductive rates during years when peak lemming populations occur autumn.

A change in the relationships between key species like this can have unprecedented effects on their communities and ecosystems. With a grim future ahead for cold-loving animals and ecosystems.

 

 

References

National Geographic, (2017). Explore the World’s Tundra. Available at: http://www.nationalgeographic.com/environment/habitats/tundra-biome/ [Accessed 17 Mar. 2017].

NOAA (2017). Arctic Change – Land: Permafrost. Available at: https://www.pmel.noaa.gov/arctic-zone/detect/land-permafrost.shtml [Accessed 17 Mar. 2017].

Post, E., Forchhammer, M. C., Bret-Harte, M. S., Callaghan, T. V., Christensen, T. R., Elberling, B., … & Ims, R. A. (2009). Ecological dynamics across the Arctic associated with recent climate change. Science, 325(5946), 1355-1358.

Ims, R. A., & Fuglei, E. V. A. (2005). Trophic interaction cycles in tundra ecosystems and the impact of climate change. Bioscience, 55(4), 311-322.

Killengreen, S. T., Ims, R. A., Yoccoz, N. G., Bråthen, K. A., Henden, J. A., & Schott, T. (2007). Structural characteristics of a low Arctic tundra ecosystem and the retreat of the Arctic fox. Biological Conservation, 135(4), 459-472.

Putkonen J, Roe G. 2003. Rain-on-snow events impact soil temperatures and affect ungulate survival. Geophysical Research Letters 30: 1188.

Heijmans, M. M. P. D., van Huissteden, J., Li, B., Wang, P., Limpens, J., Berendse, F., & Maximov, T. C. (2016). Can wet summers trigger permafrost collapse at a Siberian lowland tundra site?. INTERNATIONAL CONFERENCE ON PERMAFROST, 2016-06-20/2016-06-24

Hobbie, J. E., Shaver, G. R., Rastetter, E. B., Cherry, J. E., Goetz, S. J., Guay, K. C., … & Kling, G. W. (2017). Ecosystem responses to climate change at a Low Arctic and a High Arctic long-term research site. Ambio, 46(1), 160-173.

 

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Green Invasion on the Arctic Tundra

Posted on by Isabelle Mills

As the 24-hour summer sun melts the long winter snow, a flush of green emerges from the cold, frozen landscape. In recent years unexpected visitors have migrated into the harsh environment that 50 years ago would have succumbed to the cold. Rising global temperatures and atmospheric carbon dioxide (CO2), particularly since the turn of the millennia, is allowing shrubs and spruce (Reid, n.d.) found further south in boreal forests to survive the new tundra conditions.

This is a typical Tundra environment during the summer period. The soil is either permanently or semi-permanently frozen and the vegetation is dominated by mosses, lichens and grasses that clump together to withstand the strong cold winds. In the winter temperatures average -34C and in the summer 3-12C (NHPTV.org, 2017).
This is a typical Tundra environment during the summer period. The soil is either permanently or semi-permanently frozen and the vegetation is dominated by mosses, lichens and grasses that clump together to withstand the strong, cold winds. In the winter temperatures average -34 degrees Celsius and in the summer 3-12 degrees Celsius (NHPTV.org, 2017).

The effect of modern humans’ industrial activity discharging Carbon Dioxide (CO2) into the atmosphere has caused the average global temperature to rise 0.99 °C relative to 1951-1980 figures (NASA, 2017). Due to the nature of the environment, Arctic regions are more sensitive and experience the warming effect two to three degrees higher than the global average (Ramsayer, 2016).

The combination of increased CO2, higher temperatures, and subsequently longer growing seasons is in fact benefitting some vegetation.  Satellite images have shown a 29.4 percent increase of greening in the far north of Russia, Scandinavia, Alaska and Canada where previously only limited vegetation could grow (Ramsayer, 2016). However, as with all dramatic changes there are winners and loser and many mosses and lichens have been declining.

Here we can see the encroachment of the boreal forest treeline on the tundra environment. Species include Black Spruce (Picea mariana). Though the trees are sparsely located and thin, it highlights how the ecosystem is becoming more habitable to a new range of vegetation (Goldstone, 2013).
Here we can see the encroachment of the boreal forest treeline on the tundra environment. Species include Black Spruce (Picea mariana). Though the trees are sparsely located and thin, it highlights how the ecosystem is becoming more habitable to a new range of vegetation (Goldstone, 2013).

There are multiple reasons for Arctic greening, one being increased temperature. When the temperature rises closer to its optimum growing temperature the rate of the chemical processes such a photosynthesis and enzymes function within the plant improves dramatically. The efficiency of photosynthesis (process of absorbing light energy to react with CO2 to produce sugars) improves because the quantity of photosynthetic pigments increases under warmer temperatures (Saxe et al., 2002). When exposed to temperatures above the optimum, it can cause proteins to become inactive, inhibiting CO2 fixation needed for photosynthesis (Shailes, 2013). This may be one of the reasons behind decline in the native mosses and lichens in the region.

Higher temperatures also create a longer growing season (previously 50-60 days) (Krajick, 2016) allowing the frozen soil to thaw. Species including Alder can now successfully compete as their seedlings are able to grow quickly allowing the roots to take hold and withstand frost cover at the end of the growing season.

Arctic Greening has also been influenced by rising CO2 acting as a fertiliser for plants in soils with a low moisture content. CO2 is a limiting factor in photosynthesis, with more readily available, photosynthesis can function more efficiently (Saxe et al., 2002). Studies have shown that plants have the ability to photosynthesise up to 40 percent faster when they are subjected to CO2 concentrations between 475 and 600ppm (Pearson et al., 2013).

The Arctic region of interest covers an area of 10 million square miles. The average rate of greening has been identified as 29.4%. Some areas highlighted in green and blue showed a percentage growth of 34-41%. The areas identified in orange and red experienced a decrease in greening by 3 to 5%. These images were developed from the information gathered by MODIS satellite instruments (Hansen et al., 2013).
The Arctic region of interest covers an area of 10 million square miles. The average rate of greening has been identified as 29.4%. Some areas highlighted in green and blue showed a percentage growth of 34-41%. The areas identified in orange and red experienced a decrease in greening by 3 to 5%. These images were developed from the information gathered by MODIS satellite instruments (Hansen et al., 2013).

Temperatures are expected to rise alongside CO2 concentrations, inevitably changing the structure of the Arctic region and enhancing the greening effect leading to further warming. This will cause further encroachment of the treeline and a decline in mosses and lichens which will in turn alter the ecosystem relationships and dynamics between plant and animal species (Pearson et al., 2013).

 

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In Text References: 

Krajick, K. (2016). Where Trees Meet Tundra, Decoding Signals of Climate Change. [Blog] State of the Planet. Available at: http://blogs.ei.columbia.edu/2016/11/16/where-trees-meet-tundra-decoding-signals-of-climate-change/ [Accessed 16 Mar. 2017].

NASA. (2017). Climate Change: Vital Signs of the Planet. [online] Available at: https://climate.nasa.gov/vital-signs/carbon-dioxide/ [Accessed 17 Mar. 2017]. [Accessed 18 Mar. 2017].

Pearson, R., Phillips, S., Loranty, M., Beck, P., Damoulas, T., Knight, S. and Goetz, S. (2013). Shifts in Arctic vegetation and associated feedbacks under climate change. Nature Climate Change, 3(7), pp.673-677.

Ramsayer, K. (2016). NASA Studies Details of a Greening Arctic. [Blog] NASA. Available at: https://www.nasa.gov/feature/goddard/2016/nasa-studies-details-of-a-greening-arctic [Accessed 20 Mar. 2017].

Reid, R. (n.d.). Explore the World’s Tundra. [online] National Geographic. Available at: http://www.nationalgeographic.com/environment/habitats/tundra-biome/ [Accessed 19 Mar. 2017].

Saxe, H., Cannell, M., Johnsen, Ø., Ryan, M. and Vourlitis, G. (2002). Tree and forest functioning in response to global warming. New Phytologist, 149(3), pp.369-399.

Shailes, S. (2013). It’s getting hot out here: the challenges facing plants in hot weather. [Blog] Plant Scientist. Available at: https://plantscientist.wordpress.com/2013/07/23/its-getting-hot-out-here-the-challenges-facing-plants-in-hot-weather/ [Accessed 16 Mar. 2017].

 

Image References:

Goldstone, H. (2013). Dramatically Greener Arctic in Near Future. [Blog] Capean Islands. Available at: http://capeandislands.org/post/new-research-predicts-dramatically-greener-arctic-near-future#stream/0 [Accessed 19 Mar. 2017].

Hansen, K., Cole, S. and Mariaire, R. (2013). NASA – Amplified Greenhouse Effect Shifts North’s Growing Seasons. [online] NASA. Available at: https://www.nasa.gov/topics/earth/features/growth-shift.html [Accessed 19 Mar. 2017].

NHPTV.org. (2017). Tundra. [online] Available at: http://www.nhptv.org/wild/tundra.asp [Accessed 21 Mar. 2017].

 

 



When Nelly The Mastodon packed her Trunk….

Posted on by William Townsend

The Mammoth Steppe

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Figure 1. An artist’s rendition of the Mammoth Steppe

The “mammoth steppe” ecosystem existed approximately 11 thousand years ago, during the Pleistocene epoch (University of California Museum of Palaeontology, 2011). This ecosystem was typified by high species densities, highly productive vegetation and high levels of nutrient cycling. (Pleistocene Park, 2017). In appearance it was very similar to the modern tundra ecosystem seen in northern latitudes such as Iceland and Northern Canada. Within these ecosystems the predominant species were large herbivores; Steppe Bison (Bison priscus), Horses (Equus lambei), Musk ox (Boothrium bombifrons) and Mammoths (Mammuthus primigenius) (Guthrie, 1989; Merck, 2011) but other large herbivorous species included the woolly rhino and giant deer (Van Kolfschoten, 2007) were also present in less abundance.

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Figure 2. The extent of the Mammoth Steppe across the landmass Beringia

Whilst this is not an exhaustive list of the species present, as exemplified by the fossil record presented in Cooper (2008), this megafaunal community provides a good example of the prevalent community assemblage of the ecosystem. An example of this ecosystem is “Beringia” the landmass present when the bed of the Bering sea was exposed linking Siberia and North America.

 

How The Mammoth Went Extinct And Took Its Habitat With It

There are two prevalent theories as to how species within these ecosystems went extinct; The impacts of Climate change and the impacts of overhunting by humans. In terms of “biogeographic population theory” these constitute the environmental and biotic constraints; the limits placed upon a species by the environment and by other species, however both are driven by a change in climate. The direct impact of environmental change was increased seasonal variation and widely fluctuating climates, putting stress on many species and limiting populations. Indirectly this increased the pressure between species, with declines in food sources due to altered growing seasons resulting in resident humans relying more heavily on large mammal hunting. The combination of environmental and biotic pressures it is thought, resulted in the extinction of many large  grazing species in this ecosystem and it is argued, resulted in a shift away from the tundra and towards higher productivity systems (Pleoistocene Park, 2017).

 

Why Does It Matter?

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Figure 3. The modern extent of the tundra ecosystem

When applied to modern tundra ecosystems, which share much of the same range as the “Mammoth steppe”, these theories could have several implications. With modern human driven climate change, species that are highly sensitive to changes like snow cover reduction and rising temperatures in the modern day tundra ecosystems could be at risk. This is visible in Caribou populations, which show a decline correlated with rising temperature and rainfall (Vors and Boyce, 2009) and who’s populations may be influenced by plant community shifts driven by abiotic changes.

Musk ox populations also show variability as a result of forage ability, habitat availability, and infectious diseases. increasing temperature and humidity (Ytrehus, et al., 2008).

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Figure 4. An artist’s rendition of the tundra ecosystem

With the loss of such prevalent grazing herbivorous species could come a resultant ecosystem shift as seen during the Pleistocene quaternary extinction, and result in the loss of the modern tundra ecosystem.

Word Count: 495

 

Bibliography

Cooper, C.L. (2008) Pleistocene Fauna. Available at: http://www.uky.edu/OtherOrgs/KPS/poky/files/pokych10-01-29.pdf (Accessed: 1 March 2017).

Lenart, E.A., Bowyer, R.T., Hoef, J.V. and Ruess, R.W. (2002) ‘Climate change and caribou: Effects of summer weather on forage’, Canadian Journal of Zoology, 80(4), pp. 664–678. doi: 10.1139/z02-034.

Merck, J. (2011) Alaska 2007 – the mammoth Steppe. Available at: https://www.geol.umd.edu/~jmerck/alaska/alaska11pleistocene.html (Accessed: 1 March 2017).

Pleistocene Park (2017) Pleistocene park: Restoration of the mammoth Steppe Ecosystem. Available at: http://www.pleistocenepark.ru/en/background/ (Accessed: 1 March 2017).

University of California Museum of Paleontology (2011) The Pleistocene epoch. Available at: http://www.ucmp.berkeley.edu/quaternary/pleistocene.php (Accessed: 1 March 2017).

Van Kolfschoten, T. (2007) The collapse of the mammoth Steppe ecosystem. Available at: http://www.nwo.nl/en/research-and-results/research-projects/i/57/3357.html (Accessed: 1 March 2017).

Vors, L.S. and Boyce, M.S. (2009) ‘Global declines of caribou and reindeer’, Global Change Biology, 15(11), pp. 2626–2633. doi: 10.1111/j.1365-2486.2009.01974.x.

Ytrehus, B., Bretten, T., Bergsjø, B. and Isaksen, K. (2008) ‘Fatal pneumonia Epizootic in musk ox (Ovibos moschatus) in a period of extraordinary weather conditions’, EcoHealth, 5(2), pp. 213–223. doi: 10.1007/s10393-008-0166-0.