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Walking on thin ice – Why we should care about the polar bear

Posted on by James Symington

solo-bear

I’m sure you’ve all seen enough TV adverts showing polar bears floating on small patches of ice by now to just roll your eyes and change channel. I’m also sure you’ve thought to yourself “Why is it always polar bears?” and “Why should I care?”. I’d like to explain why polar bears and, more broadly, arctic ice are so important and why, instead of averting our eyes, we should be paying more attention than ever.

Most scientists agree that polar bears are in serious trouble. With their habitat and hunting ground of choice, arctic sea ice, disappearing at a rate of 13 percent per year (Nsidc.org, 2017) polar bears are getting thinner (Obbard et al., 2016) and those cute baby polar bears are bearing the brunt of it (Pagano et al., 2012). Polar bears use the ice as platforms to catch their main source of food, ringed and harp seals, with a surprising amount of stealth and guile for 2.5m long, 700 kilo apex predators.

Derek never saw it coming.
Derek never saw it coming.

With longer swims required to reach the ice each year, fewer polar bear cubs can make the swim (Pagano et al., 2012 and Hassol, 2004). No more cubs mean no more polar bears. No more polar bears would have enormous knock-on effects on the artic ecosystem. For example, if harp seal numbers were to increase due to lack of predation, numbers of Northern shrimp would drop significantly (Hassol, 2004). Northern shrimp have no fewer than 16 predators and so act as a lynchpin for a significant portion of the food web (Parsons, 2005).

With a 0.48°C increase in global temperatures between 1984 and 2012, Winter ice cover in the arctic saw an almost 50% decrease. Check out this GIF from NASA for a better idea: http://photojournal.jpl.nasa.gov/archive/PIA14385.gif
With a 0.48°C increase in global temperatures between 1984 and 2012, Winter ice cover in the arctic saw an almost 50% decrease. Check out this GIF from NASA for a better idea: http://photojournal.jpl.nasa.gov/archive/PIA14385.gif

Why does this matter then? More than anything, the plight of the polar bear represents our success or failure in safeguarding our planet. Breaking apart the food web of the arctic doesn’t just affect the ecosystem there; If we continue the path we are currently on, then we risk damaging the ecosystem to the point where we lose out on 7 million tons of fish every year (Hassol, 2004 and EPA, 2017).

fishing-graph

It’s no coincidence that the loss of sea ice (B) is directly correlated with a drop in Northern shrimp (A) (Pandalus borealis). Cod can migrate to other areas of ice with more ease than shrimp so can maintain reasonable numbers for the time being.
It’s no coincidence that the loss of sea ice (B) is directly correlated with a drop in Northern shrimp (A) (Pandalus borealis). Cod can migrate to other areas of ice with more ease than shrimp so can maintain reasonable numbers for the time being.

Damage to the arctic ecosystem doesn’t stop at polar bears and fish. The effects of arctic ice reduction will be felt all over the globe from rising sea levels to the loss of cold-adapted species, such as the humble lemming. With enough warming, those cold-adapted species will struggle to survive while other invasive species will suddenly have massive stretches of land made available to them (Ware, 2013). The most serious problem, however, is that we may have set off a chain of events that is running far out of our control.

If left unchecked this feedback loop will be disastrous for humanity, with more frequency storms, more forest fires and some regions could even turn into new deserts.
If left unchecked this feedback loop will be disastrous for humanity, with more frequency storms, more forest fires and some regions could even turn into new deserts.

It isn’t all doom and gloom of course, its predicted that we’ll see more trans-arctic marine transport and (unfortunately) better access to arctic oil deposits which will help off-set the damage (Hassol, 2004 and Block, 2016). The question we need to ask ourselves, however, is “Will it be worth it?

A protest from Sierra club, a group of environmental activists, attempting to stop a mid-2000s arctic oil drilling project named “Liberty project” from Hilcorp.
A protest from Sierra club, a group of environmental activists, attempting to stop a mid-2000s arctic oil drilling project named “Liberty project” from Hilcorp.

Word count: 485

References:

  • Nsidc.org. (2017). Arctic Sea Ice News and Analysis | Sea ice data updated daily with one-day lag. [online] Available at: http://nsidc.org/arcticseaicenews/ [Accessed 20 Mar. 2017].
  • Obbard, M., Cattet, M., Howe, E., Middel, K., Newton, E., Kolenosky, G., Abraham, K. and Greenwood, C. (2016). Trends in body condition in polar bears ( Ursus maritimus ) from the Southern Hudson Bay subpopulation in relation to changes in sea ice. Arctic Science, 2(1), pp.15-32.
  • Pagano, A., Durner, G., Amstrup, S., Simac, K. and York, G. (2012). Long-distance swimming by polar bears ( Ursus maritimus ) of the southern Beaufort Sea during years of extensive open water. Canadian Journal of Zoology, 90(5), pp.663-676.
  • Hassol, S. (2004). Impacts of a warming Arctic. 1st ed. [ebook] Cambridge: Cambridge University Press. Available at: http://www.cambridge.org/gb/academic/subjects/earth-and-environmental-science/climatology-and-climate-change/impacts-warming-arctic-arctic-climate-impact-assessment?format=PB&isbn=9780521617789 [Accessed 20 Mar. 2017].
  • Parsons, D. (2005). Predators of northern shrimp,Pandalus borealis(Pandalidae), throughout the North Atlantic. Marine Biology Research, 1(1), pp.48-58.
  • gov. (2017). Climate Impacts on Ecosystems | Climate Change Impacts | US EPA. [online] Available at: https://www.epa.gov/climate-impacts/climate-impacts-ecosystems [Accessed 20 Mar. 2017].
  • Ware, C. (2013). Arctic at risk from invasive species. [Blog] The Ecologist. Available at: http://www.theecologist.org/News/news_analysis/2173097/arctic_at_risk_from_invasive_species.html [Accessed 20 Mar. 2017].
  • Block, B. (2016). Arctic Melting May Lead To Expanded Oil Drilling | Worldwatch Institute. [online] Worldwatch.org. Available at: http://www.worldwatch.org/node/5664 [Accessed 20 Mar. 2017].

 

Figures:

Figure 1 – Polar bear on ice – Available from: http://www.endangeredpolarbear.com/uploads/1/4/2/4/14243313/2894929.png

Figure 2 – Polar bear hunting seal – Available from: https://i.ytimg.com/vi/MC26JK9nk-8/maxresdefault.jpg

Figure 3 – Arctic ice loss from 1984-2012 – Available from: https://intellihub.com/wp-content/uploads/2015/01/1348775537_2624_composite.jpg

Figure 4A – Past and predicted fishing – Available from Reference number 3.

Figure 4B – Arctic sea ice loss graph – Available from: http://nsidc.org/images/arcticseaicenews/20101004_Figure3.png

Figure 5 – Arctic warming positive feedback loop – Available from: http://www.climateemergencyinstitute.com/uploads/arctic_fb1.png

Figure 6 – The Arctic is not for sale – Available from: http://www.k-zap.org/wp-content/uploads/2015/12/arctic-drilling.jpg



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.

 

screen-shot-2017-03-22-at-22-35-14

                                        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).

screen-shot-2017-03-22-at-21-44-41

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.

 

Word count [496]

 

 

 



King Louie’s Last Stand: Are we set to lose Southeast Asia’s jungle kingdoms?

Posted on by Robert Morris

With his charm, charisma and infectious enthusiasm for big band jazz, it was the Jungle Book’s King Louie who first introduced many of us to the rainforests of Southeast Asia. But beyond now sounding an awful lot like Christopher Walken, what’s happened to the old Orang-utan over the last 50 years?

Unfortunately, there’s little to report in the way of good news. Despite our affections, Orang-utans, along with much of their rainforest ecosystem, are struggling to survive. Mowgli, as it turns out, grew up…and in doing so, discovered that selling oil derived from palm nuts is a quick and easy means of turning a profit (McCarthy et al., 2012).

orang-utan
Times are tough for Orang-utans. Image credit: YeeChao, Koh via Flickr

As a result, the production of palm oil has become big business throughout the developing world, but particularly in Southeast Asia (Koh and Wilcove, 2007). The implications for rainforest ecosystems however, are dire. In order to produce palm oil, vast areas of rainforest must be cleared to make way for plantations of oil palms.

Such a widespread loss of habitat poses an obvious threat to iconic species such as the Orang-utan who depend on the rainforest for survival. However, the problem of palm oil may run deeper.

sun-bear
It’s not just Orang-utans that are endangered by land use change. Deforestation has likely contributed to a 30% decline (Fredriksson et al., 2008) in the population of Sun Bears and resulting human conflict is well documented (Wong, et al., 2015).  Image credit: skepticalview via Flickr
The region’s famous Black Panthers (left), or rather, melanistic Indochinese Leopards (AKA, Bagheera (right)), are struggling, having lost 93% of their Asian habitat (Hance, 2016).  Image credit: (left) Tambako via Flickr, (right) Disney
The region’s famous melanistic Leopards (left), AKA Bagheera (right), are also struggling, having lost 93% of their Asian habitat (Hance, 2016).
 Image credit: (left) Tambako via Flickr, (right) Disney

The emerging field of complexity science suggests additional concerns in that we should consider also the nature of deforestation patterns and the effect this has on the capacity of rainforests to recover from stress. Only then, can we hope to effectively conserve rainforest ecosystems.

Unsurprisingly, deforestation occurs largely along the fringes of roads. However, this results in not only habitat loss, but also habitat fragmentation. In isolating patches of rainforest within traffic laden road networks, organisms become trapped. Reducing the connectivity of an ecosystem in this way can in turn undermine its resilience (Pardini et al., 2010); that is, its ability to respond and recover from stress events.

For example, if a fire were to break out in an isolated forest surrounded by roads, mammal species may find it difficult to escape and would therefore perish. Furthermore, without the movement of organisms to transport seeds, some plant species could encounter difficulty recolonising the area once the flames have subsided.

It is worth noting that the barriers between isolated rainforest stands expand from busy roads to entire palm oil plantations spanning hundreds of square kilometres. When we consider that the plantations themselves can form barriers to even some bird species (Knowlton et al., 2017), the need for an urgent and effective solution becomes clear.

Indonesia, 2007.
Approximately 45% of the palm oil plantations in Southeast Asia were pristine rainforest in 1989 (Vijay et al., 2016). Image credit: CIFOR via Flickr

Alongside traditional restoration methods, the development of forest corridors may provide the answer (Sodhi et al., 2010), with similar projects having achieved success elsewhere in the world (Wyborn, 2011). In providing a means for organisms to travel between detached rainforest patches, ecosystem managers can enhance the resilience of the habitat and help to ensure its continued survival.

However, effective implementation must be swift. Else we run the risk of losing King Louie and his jungle kingdom, forever.

Click here more info on how ecosystems can be managed to improve their resilience.

Can King Louie be saved? Image credit: CIFOR via Flickr
Can King Louie be saved?
Image credit: CIFOR via Flickr

Word count: 500

References:

Fredriksson, G., Steinmetz, R., Wong, S. and Garshelis, D.L. (IUCN SSC Bear Specialist Group) (2008) Helarctos malayanus. The IUCN Red List of Threatened Species 2008. Available from: http://dx.doi.org/10.2305/IUCN.UK.2008.RLTS.T9760A13014055.en. [Accessed 14 March 2017].

Hance, J. (2016) Another big predator in Southeast Asia faces extinction. The Guardian, 31 August. Available from: https://www.theguardian.com/environment/radical-conservation/2016/aug/31/leopards-tigers-asia-snares-poaching-endangered-extinction [Accessed 14 March 2017].

Knowlton, J.L., Phifer, C.C., Cerqueira, P.V., Barro, F.D.C., Oliveira, S.L., Fiser, C.M., Becker, N.M., Cardoso, M.R., Flaspohler, D.J. and Dantas Santos, M.P. (2017) Oil palm plantations affect movement behavior of a key member of mixed-species flocks of forest birds in Amazonia, Brazil.Tropical Conservation Science, 10, 1-10.

Koh, L.P. and Wilcove, D.S. (2007) Cashing in palm oil for conservation. Nature, 448 (7517), 993-994.

McCarthy, J.F., Gillespie, P. and Zen, Z. (2012) Swimming upstream: Local Indonesian production networks in “globalized” palm oil production.World Development, 40 (3), 555-569.

Pardini, R., Bueno, A.dA., Gardner, T.A., Prado, P.I. and Metzger, J.P. (2010) Beyond the fragmentation threshold hypothesis: regime shifts in biodiversity across fragmented landscapes.PloS one, 5 (10), e13666.

Sodhi, N.S., Koh, L.P., Clements, R., Wanger, T.C., Hill, J.K., Hamer, K.C., Clough, Y., Tscharntke, T., Posa, M.R.C. and Lee, T.M. (2010) Conserving Southeast Asian forest biodiversity in human-modified landscapes.Biological Conservation, 143 (10), 2375-2384.

Vijay, V., Pimm, S.L., Jenkins, C.N. and Smith, S.J. (2016) The impacts of oil palm on recent deforestation and biodiversity loss. PLoS One, 11 (7), e0159668.

Wong, W.M., Leader-Williams, N. and Linkie, M. (2015) Managing human-sun bear conflict in Sumatran agroforest systems.Human Ecology, 43 (2), 255-266.

Wyborn, C. (2011) Landscape scale ecological connectivity: Australian survey and rehearsals.Pacific Conservation Biology, 17 (2), 121-131.



Why those holiday snaps may never look the same again….

Posted on by Lauren Scrace

From Sunday night Attenborough documentaries, to gap year photos from people you haven’t seen for years, we’re becoming increasingly informed about the world around us, enticing us to explore.

The Great Barrier Reef stretching the Queensland coastline is such a vast natural spectacle it can be seen from space. This complex ecosystem is home to over 450 types of coral and provides a habitat for marine creatures ranging from tropical fish to turtles (1), making it a popular holiday destination but for how much longer?

Lizard Island, Luxury Lodges of Australia, Queensland
Unbleached Coral reef community. Queensland (2)

This beautiful system is under threat from rising sea temperatures, putting stress upon the corals causing them to release the algae from their tissues leaving only ghostly white calcium skeletons remaining. Both the coral and the algae rely on their partnership for energy and safety.

These ‘bleached’ corals are unsustainable and will perish within weeks if the sea temperature fails to return to within tolerable ranges. Due to the certainty of rising ocean temperatures, restoration success is unlikely and the devastation likely to continue. (1)

Once a year the reef engages in mass reproduction, triggered by temperature and the lunar cycle, this supports continued reef biodiversity as well as providing an ample source of food for reef dwellers. A shift in the temperature cues for reproduction will have severe impacts on community biodiversity as compared to natural incidents global shifts cause a greater long term impact, reducing the possibility of recovery (3).

exclusive-coral-bleaching-in-new-caledonia2-1120x747
Coral bleaching event. Picture credit- The Ocean Agency / XL Catlin Seaview Survey / Richard Vevers  (4)

Environmental change that impacts the structure of the corals will also affect their functional ability within the community. (5) Corals provide shelter for many marine species, allow for protected migration and increased genetic flow through coral corridors.  This change alter the community structure and exasperate the global mass extinction we are currently experiencing.

So what is actually happening?

Global activities are impacting the future of this system dramatically, through climate change and our ever-increasing carbon footprint.

Corals extract calcium carbonate (the substance that forms eggshells) from the surrounding sea water to build the reef, using energy utilized from the algae within their structures. Each species builds differently to give beautifully diverse reefs, supporting creatures from zooplankton to green turtles.

Increasing atmospheric CO2, is absorbed by the oceans where its combined with seawater to produce an acid, leading to ocean acidification. This reduces the concentration of carbonate ions available for use by the corals to build their structures. (6)

These global changes aren’t the only driver of community shifts. On a local scale, flooding in Queensland has caused sediment and pesticide run off into the oceans. This increased nutrient input is devastating to a system reliant on diversity (7,8),  where some species are more susceptible to change than others, causing a decline in both population density and biodiversity.

So our holiday snaps might never look the same again… To mitigate this change we need to alter our way of life, just travelling to see them impacts their survival! But keep snapping and keep people talking, its the only way we are going to make change!

 

5.8 tonnes of CO2 is released per person during a flight from London to Darwin Australia!! 
Flight # Details: Tonnes CO2
1 Return From London Gatwick to Darwin Australia 1 passenger 5.8

 

[500 Words]

 

References

  1. Australia’s Coral Reefs under Threat from Climate Change by Lesley Hughes, Will Steffen and Martin Rice (Climate Council of Australia).
  2. Great Barrier Reef | Australia’s Great Natural Wonder”. Great Barrier Reef. (2017). 21 Mar. 2017.
  3. Nyström, M., Folke, C., & Moberg, F. (2000). Coral reef disturbance and resilience in a human-dominated environment.Trends in Ecology & Evolution, 15(10), 413-417.
  4. The Ocean Agency. 2016. THE 3RD GLOBAL CORAL BLEACHING EVENT – 2014/2017. Available at: http://www.globalcoralbleaching.org/#essential-facts. [Accessed 21 March 2017].
  5. Richmond, R. H. (1993). Coral reefs: present problems and future concerns resulting from anthropogenic disturbance.American Zoologist, 33(6), 524-536.
  6. Hoegh-Guldberg, O., Mumby, P. J., Hooten, A. J., Steneck, R. S., Greenfield, P., Gomez, E., & Knowlton, N. (2007). Coral reefs under rapid climate change and ocean acidification.science, 318(5857), 1737-1742.
  7. Mongin, M., Baird, M. E., Tilbrook, B., Matear, R. J., Lenton, A., Herzfeld, M., & Duarte, C. M. (2016). The exposure of the Great Barrier Reef to ocean acidification.Nature communications, 7.
  8. Dubinsky, Z. V. Y., & Stambler, N. (1996). Marine pollution and coral reefs.Global change biology, 2(6), 511-526.


Humanity must stop neglecting changes in Seagrass Meadows before disaster?

Posted on by Anonymous

Seagrass meadows are a vital habitat and food source for many endangered species but these crucial habitats are under threat from environmental change caused by human impacts climate change, coastal developments, fishing and aquaculture (Waycott etal, 2009).

Figure 1- Manatee feeding on seagrass (USGS, 2016)
Figure 1- Manatee feeding on seagrass (USGS, 2016)

Climate Change

Climate change will cause a wide variety of impacts on the oceans which will effect seagrasses increasing water temperatures will lead to increased instances of seagrass die off, ocean acidification caused damaged to the cells plants require to photosynthesize and grow (Repolho et al, 2017).

As seagrass requires shallow habitats as sea levels rise there will be a loss of seagrass in deeper areas of their range seagrasses will move shoreward this trend is similar to trends that are being seen from increased amounts of sediments within the water as they will lack the sunlight to photsynthesise (Davis et al, 2016).

Coastal Developments

The construction of ports, artificial beaches and the reclamation of land, the adding of material to the water to fill in the area, this leads to more sediments within the water. The increased amount of sediments in the water can lead to seagrass beds being completely buried by the sediment and stopping plants from photosynthesising which it needs to survive, during the construction of the Pointe-Rouge Harbour over 68ha of seagrasses were lost due to water sediment and 11ha destroyed by construction (Boudouresque et al, 2009).

Figure 2- The Light grey shows dead seagrass and the dark grey living seagrass after the laying of a cable between two islands in the South of France (Boudouresque et al, 2009)
Figure 2- The Light grey shows dead seagrass and the dark grey living seagrass after the laying of a cable between two islands in the South of France (Boudouresque et al, 2009)

 

Fishing and Aquaculture

A trawler can uproot between 99,000-363,000 shoots during a trawl and in some areas of the Mediterranean over 80% of the seagrass meadows have been destroyed due to trawling (Boudouresque et al, 2009). Aquaculture, mainly fish farms, can cause a process called eutrophication, an excessive increase in nutrients heading into a body of water leading to high algal growth, because of the nutrients from uneaten food and excretion from the fish as it is focussed in one area around the fish farm this causes the reduction in size of the plants in the area due to reduced light reaching the plants, leading to a regression of the plants in the areas around fish farms (Ruiz et al, 2001).

pic-3
Figure 3- Changes in seagrass area by coastlines and in most coastlines more studies report a decrease (Waycott et al, 2009).

Future of Endangered Species

Dugongs, sea turtles and manatees all directly depend upon seagrass in many tropical regions for food and with decreases in seagrass globally, figure 3, they is likely to be further pressure put onto these already endangered species (Waycott et al, 2009), and if humanity does not take steps to solving the problems mentioned here the future of these iconic species is in real danger.

 

 

Reference List

Boudouresque, C., Bernard, G., Pergent, G., Shili, A., Verlaque, M., (2009), Regression of Mediterranean seagrasses caused by natural processes and anthropogenic disturbances and stress: a critical review, Botanica Marina, 52, 395-418

Davis, T., Harasti, D., Smith, S., Kelaher., (2016), Using modelling to predict impacts of sea level rise and increased turbidity on seagrass distributions in estuarine embayments, Estuarine, Coastal and Shelf Science, 181, 294-301

Repolho, T., Duarte, B., Dionísio, G., Paula, J., Lopes, A., Rosa, I., Grilo, T., Caçador, I., Calado, R. and Rosa, R. (2017). Seagrass ecophysiological performance under ocean warming and acidification. Scientific Reports, 7, p.41443.

Ruiz, J., Perez, M., Romero, J., (2001), Effects of Fish Farm Loadings on Seagrass (Posidonia oceanica) Distribution, Growth and Photosynthesis, Marine pollution bulletin, 42(9), 749-760

USGS, (2016). Manatees [online] Available at: https://www.usgs.gov/centers/wetland-and-aquatic-research-center-warc/science-topics/manatees [Accessed 20 Mar. 2017].

Waycott, M., Duarte, C., Carruthers, T., Orth, R., Dennison, W., Olyarnik, S., Calladine, A., Fourqurean, J., Heck, K., Hughes, A., Kendrick, G., Kenworthy, W., Short, F. and Williams, S., (2009). Accelerating loss of sea grass across the globe threatens coastal ecosystems,. PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 106(30), 12377-12381

 

Word Count – 489

 

 

 



Will Intensifying Agriculture Save Us, or Starve Us?

Posted on by Deanna Fox

The surge in human population in recent years is predicted to reach an unprecedented 9.1 billion people by 2050 – a 14% increase of our current population (McKee et al., 2004). This epidemic of population growth means we are faced with the daunting challenge of attaining sustainable increase in crop production to meet the increasing food demands.

Anthropogenic disturbance in natural landscapes is one of the largest contributors to biodiversity loss. Here is the aftermath of land clearance for palm oil plantations, Borneo. Photo credit: Rhett A. Butler (2012). Available at: https://news.mongabay.com/2012/09/agriculture-causes-80-of-tropical-deforestation/
Anthropogenic disturbance in natural landscapes is one of the largest contributors to biodiversity loss. Here is the aftermath of land clearance for palm oil plantations, Borneo (Butler, 2012).

Global agricultural intensification has increased our food production to meet this demand through conversion of natural to simplified agricultural landscapes and escalating the application of agrochemicals such as pesticides and fertilisers (Matson et al., 1997). This simplification is a major cause of the accelerating loss of biodiversity, which affects ecological processes such as nutrient recycling, carbon storage and pollination (Flynn et al., 2009).

A biotic communities’ functional traits (i.e. characteristics) influences ecosystem functioning through mediating changes in biotic processes, such as predation and competition (Wood et al., 2015). For example, where there are collectively few traits in a community, circumstances of “niche overlap” are common, meaning ability to utilise a broad range of resources within a community decreases, whilst competition for a narrow selection resources increases (Flynn et al., 2009).

Figure 1: Theoretical total functional traits in natural, low-intensity agriculture, intensive agriculture, and managed through polyculture settings4.
Figure 1: Theoretical total functional traits in natural, low-intensity agriculture, intensive agriculture, and managed through polyculture settings (Wood et al., 2015).

Intensive agriculture may degrade (A) the number of functional traits in a given area (functional trait space). However, theoretically implementing adequate management strategies promoting multi-species crops (polycultures) may aid limited recovery of total functional traits (B), recovery to the levels of natural counterparts (C), or even exceed this (D) by endorsing evolution of new species with novel traits (figure 1).

Biodiversity loss through agricultural intensification has been reported for birds, insects, plants and mammals, along with functional trait diversity (Flynn et al., 2009).

 

 

 

“Between 1970 and 1990, 86% of farmland bird species had reduced ranges and 83% had declined in abundance [in Europe]” (Benton et al., 2003)

 

The resulting loss of functional traits (including foraging strategies and diet) has significant implications for the removal of insects from farmland, whereby insect subtraction is reduced. The disruptive effects this has on pest communities increases the risk of outbreaks, which not only influences community structures, but hinders crop productivity (Wood et al., 2015).

Application of pesticides to a monoculture crop in an attempt to control pest population. Photo credit Unknown. Available at: http://sitn.hms.harvard.edu/flash/2015/gmos-and-pesticides/
Application of pesticides to a monoculture crop in an attempt to control pest population (Hsaio, 2015)

Shifts toward monoculture (single-species) crops, and reduced predation, facilitates the spread of pests, increasing the risk of epidemics. Pesticides are commonly used as a control measure, although are often toxic to many species.  DDT, commonly used through the mid-20th century, accumulates in increasingly high concentrations up food chains between predators. This concentration may increase thousand-fold or more, of the content in the original source. This caused the endangerment of many predatory birds such as the peregrine falcon and kestrel through thinning their egg shells thus increasing infant mortality. Loss of top predators disrupts regulation of species populations further down the chain, unbalancing the community (Peakall, 1970).

Biodiversity loss is having severe adverse impacts on the health of our biotic communities, and therefore ecosystems. While agriculture cannot be halted all together, we could improve crop strength through diversity through implementing adequate management strategies to promote biodiversity, and use this to control pest outbreaks in an ecologically sensitive manner.

 

References

Benton, T. G., Vickery, J. A. and Wilson, J. D. (2003) ‘Farmland biodiversity: Is habitat heterogeneity the key?’, Trends in Ecology and Evolution, 18(4), pp. 182–188. doi: 10.1016/S0169-5347(03)00011-9.

Butler, R. A. (2012) Agriculture causes 80% of tropical deforestation, Mongabay. Available at: https://news.mongabay.com/2012/09/agriculture-causes-80-of-tropical-deforestation/ (Accessed: 21 March 2017).

Flynn, D. F. B., Gogol-Prokurat, M., Nogeire, T., Molinari, N., Richers, B. T., Lin, B. B., Simpson, N., Mayfield, M. M. and DeClerck, F. (2009) ‘Loss of functional diversity under land use intensification across multiple taxa’, Ecology Letters, 12(1), pp. 22–33. doi: 10.1111/j.1461-0248.2008.01255.x.

Hsaio, J. (2015) GMOs and Pesticides: Helpful or Harmful?, Harvard University: The Graduate School of Arts and Sciences. Available at: http://sitn.hms.harvard.edu/flash/2015/gmos-and-pesticides/ (Accessed: 20 March 2017).

Matson, P. A., Parton, W. J., Power, A. G. and Swift, M. J. (1997) ‘Agricultural Intensification and Ecosystem Properties.’, Science, 277(5325), pp. 504–509. doi: 10.1126/science.277.5325.504.

McKee, J. K., Sciulli, P. W., Fooce, C. D. and Waite, T. A. (2004) ‘Forecasting global biodiversity threats associated with human population growth’, Biological Conservation, 115(1), pp. 161–164. doi: 10.1016/S0006-3207(03)00099-5.

Peakall, D. B. (1970) ‘Pesticides and the reproduction of birds.’, Scientific American, 222, pp. 72–78. Available at: http://sitn.hms.harvard.edu/flash/2015/gmos-and-pesticides/.

Wood, S. A., Karp, D. S., DeClerck, F., Kremen, C., Naeem, S. and Palm, C. A. (2015) ‘Functional traits in agriculture: Agrobiodiversity and ecosystem services’, Trends in Ecology and Evolution. Elsevier Ltd, 30(9), pp. 531–539. doi: 10.1016/j.tree.2015.06.013.

 

[492 words]



Invasion of the Arctic: How warming temperatures have led to non-native species introduction

Posted on by Anonymous
Source: Animal Club (2017) Available from: http://elelur.com/mammals/arctic-fox.html
Arctic Fox (Animal Club, 2017.  Available from: http://elelur.com/mammals/arctic-fox.html)

In the eyes of an arctic fox (Alopex lagopus), the temperatures of the tundra provide seamless living conditions. Their adaptations to low temperatures make their arctic habitats suitable for them to hunt, reproduce and in turn survive. However, their survival is threatened by increasing temperatures in the arctic, as it has become more suitable for red foxes (Vulpes Vulpes), too (Killengreen et al., 2007). As the red fox invades the territory of the arctic fox, they undergo competition for land and prey. Although this has not led to a direct decline in arctic fox numbers, it can have further impacts on food webs and community dynamics within the Arctic ecosystem (Gallant et al., 2012).

This is just an example of the new reality in the Arctic; ice is melting due to increased temperatures, and the ecosystem is changing vastly (Serreze et al., 2000). Many of us are aware that global temperatures are rising due to increased greenhouse gas emissions entering the atmosphere, however the rate of temperature change varies across the globe. Where average temperatures have increased by 0.4°C over the past 150 years, it is believed that warming in arctic regions has been almost 3 times higher (IPCC, 2014).

The increased warming creates an environment which is suitable for other, non-native species (Post et al., 2009) – such as the example of the Red Fox. Species towards the South of the Arctic have increased their range, placing pressure on the existing Arctic communities (Root et al., 2003). This ‘invasion’ is not limited to animal species; invasive species in the form of plant communities can also intrude on the ecosystem. For example, the warming has allowed shrub tundra to expand into a wider variety of habitats, and Boreal forest has begun to infringe on the tundra ecosystem (Hinzman et al., 2005).

Source: Animal Photgraphics (2017) Available from: http://alaskaphotographics.photoshelter.com/image/I00009qTaSPpYpaA
Arctic Ground Squirrel. (Animal Photgraphics, 2017. Available from: http://alaskaphotographics.photoshelter.com/image/I00009qTaSPpYpaA)

Another example is of the arctic ground squirrel (Urocitellus parryii), which acts as an ecosystem engineer through its key role in the food web (Wheeler, 2011). The arctic ground squirrel burrows into vegetated land as a mechanism for survival. The burrowing action also changes the composition of the soil, which is important for other ecological processes. However, as boreal, woody forests become more prominent than the easily accessible vegetation, the arctic ground squirrel loses its habitat (Donker & Krebs, 2011).

 

 

 

Figure 1. Predicted global surface temperature change, based on carbon emissions scenarios (IPCC, 2013).
Figure 1. Predicted global surface temperature change, based on carbon emissions scenarios (IPCC, 2013).

The Arctic ecosystem is so complex that the full effects of climate change are not yet understood. This means that the invasive species described above have the potential to interrupt even more ecological processes and food webs. This could also affect human livelihood as we also rely on the stability of the food chain for survival. Furthermore, global warming is expected to cause temperatures to increase even more, dependent on emissions scenarios (Figure 1). This would cause the number of invasive species in both terrestrial and marine ecosystems to increase, threatening the existing communities to an even greater extent.

 

 

References

Donker, S. A., Krebs, C. J. (2011) Habitat Specific Distribution and Abundance of Arctic Ground Squirrels (Urocitellus parryii) in Southwest Yukon. Canadian Journal of Zoology, 89, 570-576.

Gallant, D., Slough, B. G., Reid, D. G., Berteaux, D. (2012) Arctic fox versus red fox in the warming Arctic: four decades of den surveys in north Yukon. Polar Biology, 35(9), 1421-1431.

Hinzman, L. D., Bettez, N. D., Bolton, W. R. et al. (2005) Evidence and Implications of Recent Climate Change in Northern Alaska and Other Arctic Regions. Climatic Change, 72(3), 251-298.

IPCC (2013) Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, 1535 pp.

IPCC (2014) Climate Change 2014: Synthesis Report. Contribution of Working Groups I, II and III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. IPCC, Geneva, Switzerland, 151 pp.

Killengreen, S. T., Ims, R. A., Yoccoz, N. G., Brathen, K. A., Henden, J., Schott, T. (2007) Structural Characteristics of a Low Arctic Tundra Ecosystem and the Retreat of the Arctic Fox. Biological Conservation, 135(4), 459-472.

Post, E., Forchhammer, M. C., Bret-Harte, S. M. et al. (2009) Ecological Dynamics Across the Arctic Associated with Recent Climate Change. Science, 325(5946), 1355-1358.

Root, T. L., Price, J. T., Hall, K. R., Schneider, S. H., Rosenzweig, C., Pounds, J. A. (2003) Fingerprints of Global Warming on Wild Animals and Plants. Nature, 421, 57-60.

Serreze, M. C., Walsh, J. E., Chapin, F. S., III, Osterkamp, T., Dyurgerov, M., Romanovsky, V., Oechel. W. C., Morison, J., Zhang, T., Barry, R. G. (2000) Observational Evidence of Recent Change in the Northern High Latitude Environment. Climate Change, 46, 159-207.

Wheeler, H. C. (2011) Arctic Ground Squirrels Urocitellus parryii as Drivers and Indicators of Change in Northern Ecosystems. Mammal Review, 43, 238-255.

[479 Words]



Fuelling the Fire of Climate Change

Posted on by Lara Jackson

Human activities are fuelling the fire of climate change!

Whether it’s caused by us, or exacerbated by our actions, climate change is real and it’s one of the biggest threats to ecosystems and species on earth!

Climbing global temperatures are changing weather patterns, resulting in more frequent, adverse events, such as droughts and wildfires [figure 1](Campbell et al, 2014). The scale of such environmental disturbances can be influential in determining the composition and structure of biological communities (Campbell et al, 2014).

An example of a forest wildfire.
Figure 1 – Up in flames: A wildfire burns voraciously in Arizona, USA. Available: http://wildlife.org/wildfire-toward-understanding-its-effects-on-wildlife-from-the-wildlife-professional/

A community is an assemblage of organisms of differing species that inhabit the same geographical area (Campbell et al, 2014).

 

Wildfires destroy communities that aren’t adapted to such large-scale environmental changes (Campbell et al, 2014). Although they do occur naturally, rapid land-use change, El Niño events and droughts are extending the wildfire season, intensifying the impacts in tropical environments (Campbell et al, 2014).

Fires negatively affect the biodiversity of tropical forests as they destroy the climax community; following the fire, generalist and broadly-distributed species are selected for because these pioneer species can tolerate the harsh, burnt conditions (Campbell et al, 2014). This, coupled with the increased penetration of sunlight to the forest floor, means that they dominate the under-storey, reducing the species diversity of the growing vegetation (Cochrane et al, 1999).

Furthermore, fires reduce the abundance of flowering and fruiting trees; this deters animal species which would usually be attracted to such flora from re-inhabiting the area, thus, seeds are not dispersed and the recovery of the forest is even slower (Campbell et al, 2014). In 1997-1998, 5 million hectares of tropical forest and 70% of seedlings and saplings were destroyed in Sumatra (Kinnaird et al, 1998). Subsequently, there were observable decreases in the abundance of frugivores like siamangs (Hylobates syndactylus) seen in figure 2 (Campbell et al, 2014).

A Siamang (Hylobates syndactylus), the largest of the gibbon family that experienced population declines following severe forest fires in Sumatra. Available: http://www.houstonzoo.org/blog/see-the-siamangs-like-never-before/
Figure 2 – Siamangs (Hylobates syndactylus), are the largest of the gibbon family. They experienced significant population declines following severe forest fires in Sumatra between 1997-1998 when 5 million hectares of their home was burnt to a crisp! Available: http://www.houstonzoo.org/blog/see-the-siamangs-like-never-before/

Three years after a forest fire in Brazil, there were noted increases in the sensitivity of insectivorous birds to the consequential changes in forest composition (Barlow et al, 2004). Hence, fires also displace numerous animal species that live within the forests, disrupting ecological interactions, like food-webs, that maintain biological processes (Campbell et al, 2014). Furthermore, correlations were found between burn severity and tree mortality rates after the wildfire, leading to significant changes in forest structure (Barlow et al, 2004).

The increasing frequency of wildfire events and the subsequent disturbance to the environment has the potential to cause unparalleled changes in the composition of tropical forest communities (Cochrane et al, 1999). Not only do fires severely impact the structure and quality of the flora, they decrease the species diversity of vegetation present in the forest and result in declines in abundancy of fruiting and flowering plants. Furthermore, they have knock-on consequences for the fauna inhabiting the forest. Animals are displaced, biological interactions and processes are disrupted and frugivore and bird populations decline. To reduce the large-scale environmental changes caused by wildfires, we must adjust our habits to slow the rate of climate change and moderate the impacts of global warming.

 

References:

Barlow, J. & Peres, C.A. (2004) Ecological Responses to El Nino-induced Surface Fires in Central Brazilian Amazonia: Management Implications for Flammable Tropical Forests. Philosophical Transactions of the Royal Society B, vol 359(1443):367-380

Campbell, N. Reece, J. et al (2014). Biology: A Global Approach. Pearson Education Limited. Tenth Edition.

Cochrane, M.A. & Schulze, M.D. (1999). Fire as a Recurrent Event in Tropical Forests of the Eastern Amazon: Effects on Forest Structure, Biomass and Species Composition. Biotropica, vol 31(1):2-16

Kinnaird, M.F. O’Brien, T.G. (1998) Ecological Effects of Wildfire on Lowland Rainforest in Sumatra. Conservation Biology, vol 12(5):954-956


Word Count: 499



Living on the Edge: Habitat Fragmentation in Our Rainforest Ecosystems

Posted on by Leah Line

The Brazilian Atlantic rainforest is made up of some of the most important ecosystems on earth (Magnago et al., 2014). It supports species that are not found anywhere else on the planet (Ribeiro et al., 2009). However, the rainforest is not the vast expanse of green canopy that you might imagine.

In fact, deforestation has divided the landscape. Now, more than 80% of the remaining forest is made up of fragments with an area of less than 50 hectares (Ribeiro et al., 2009). Almost half is less than 100 metres from its edges (Ribeiro et al., 2009).

Deforestation leads to isolated fragments of rainforests. Source: Bierregaard, 2016
Deforestation leads to isolated fragments of rainforests. Source: Bierregaard, 2016

The situation in the Brazilian Atlantic rainforest is not uncommon. Due to fragmentation, more than 70% of the world’s forests are now within 1 kilometre of a forest edge, impacting rainforest ecosystems across the globe (Haddad, 2015).

WHAT IS HABITAT FRAGMENTATION?

Habitat fragmentation is the division of a habitat into increasingly smaller and more isolated pieces (Haddad, 2015). In rainforest ecosystems, this is done through deforestation. Fragmentation effects the entire ecosystem, by reducing forest area, increasing isolation and increasing forest edges (Haddad, 2015).

EDGE EFFECTS

Edge effects are the ecological changes that occur at the boundaries of these habitat fragments (Laurance et al., 2016). They can include (Laurance et al., 2016)

–  Increased wind damage
–  Changes in temperature and humidity
–  Increased flooding

These effects may make the environment along the edges of fragments unsuitable for certain species, making their available habitat even smaller (Turner, 1996).

As forests become increasingly fragmented, their exposure to edge effects also increases. Source: www.summitlearning.org
As forests become increasingly fragmented, their exposure to edge effects also increases. Source: www.summitlearning.org

THE HABITAT MATRIX

The landscape surrounding forest fragments is referred to as a “matrix” of habitats (Haddad, 2015; Gascon et al., 1999). The matrix plays an important role in acting as a selective filter for the movement of species between fragments (Gascon et al., 1999). Animals that cannot survive the matrix will be unable to move across fragments. This not only makes the animals themselves at risk of decline, but if they play a role in seed dispersal (by transporting plants’ seeds in their faeces, fur or feathers) plants will also be at risk.

“Why did the cassowary cross the road? To disperse seeds.” Cassowaries are important for seed dispersal in the rainforests of New Guinea, but could be threatened due to fragmentation of their habitats. Source: Roberts, 2016
“Why did the cassowary cross the road? To disperse seeds.” Cassowaries are important for seed dispersal in the rainforests of New Guinea, but could be threatened due to fragmentation of their habitats. Source: Roberts, 2016

But, it is not all bad news: studies have found that some species, such as Amazonian frogs, possess traits that allow them to use the matrix for movement and reproduction, as well as allowing them to tolerate edge effects and survive in the remaining fragments (Gascon et al., 1999).

Some species, such as frogs, possess traits that allow them to survive habitat fragmentation in rainforests. Source: Niem, 2015
Some species, such as frogs, possess traits that allow them to survive habitat fragmentation in rainforests. Source: Niem, 2015

LOOKING TO THE FUTURE…

Considering the range of impacts, it is unsurprising that the fragmentation of rainforests is one of the greatest threats to global biodiversity (Magnago et al., 2014). And the future does not look bright; as human populations continue to rise, the extent of deforestation and fragmentation of our forests is likely to also increase (Haddad, 2015).

But all is not lost; conservation projects mitigate some negative impacts, with studies discovering types of forest that can reduce edge effects near fragment margins (Mesquita et al., 1999).

BUT WHAT CAN I DO?

Take a look at the following website by Greenpeace and see what you can do to prevent deforestation: http://www.greenpeace.org/usa/forests/solutions-to-deforestation/

[499 words]

References

Bierregaard, R., 2011. Forest fragments under research in the Biological Dynamics of Forest Fragments Project. [photograph] Reproduced in: Hance, J., 2011. Lessons from the world’s longest study of rainforest fragments. [online] Available at: https://news.mongabay.com/2011/08/lessons-from-the-worlds-longest-study-of-rainforest-fragments/ [Accessed: 21/03/17]

Gascon, C.; Lovejoy, T. E.; Bierregaard, R. O.; Malcolm, J. R.; Stouffer, P. C.; Vasconcelos, H. L.; Laurance, W. F.; Zimmerman, B.; Tocher, M. and Borges, S., 1999. Matrix habitat and species richness in tropical forest remnants. Biological Conservation, 91(2-3), pp. 223-229

Haddad, N. M.; Brudvig, L. A.; Clobert, J.; Davies, K. F.; Gonzalez, A.; Holt, R. D.; Lovejoy, T. E.; Sexton, J. O.; Austin, M. P.; Collins, C. D.; Cook, W. M.; Damschen, E. I.; Ewers, R. M.; Foster, B. L.; Jenkins, C. N.; King, A. J.; Laurance, W. F.; Levey, D. J.; Margules, C. R.; Melbourne, B. A.; Nicholls, A. O.; Orrock, J. L.; Song, D. and Townshend, J. R., 2015. Habitat fragmentation and its lasting impact on Earth’s ecosystems. Science Advances, 1(2), pp. 1-9

Laurance, W.F.; Camargo, J. L. C.; Fearnside, P. M.; Lovejoy, T. E.; Williamson, G. B.; Mesquita, R.C.G.; Meyer, C. F. J.; Bobrowiec, P. E. D. and Laurance, S.G.W., 2016. An Amazonian forest and its fragments as a laboratory of global change. pp. 407-440. In: L. Nagy, B. Forsberg, P. Artaxo (eds.) Interactions Between Biosphere, Atmosphere and Human Land Use in the Amazon Basin. Springer (Ecological Studies 227), Berlin, Alemanha.

Magnago, L. F. S.; Edwards, D. P.; Edwards, F. A.; Magrach, A.; Martins, S. V. and Laurance, W. F., 2014. Functional attributes change but functional richness is unchanged after fragmentation of Brazilian Atlantic forests. Journal of Ecology, 102(2), pp. 475-85

Mesquito, R. C. G.; Delamônica, P. and Laurance, W. F., 1999. Effect of surrounding vegetation on edge-related tree mortality in Amazonian forest fragments. Biological Conservation, 91(2-3), pp. 129-134

Niem, Y. Tree frog silhouette. [photograph] Available at: http://fotovenopilon.si/entry/jury/awards.php?section=D [Accessed: 22/03/17]

Ribeiro, M. C.; Metzger, J. P.; Martensen, A. C.; Ponzoni, F. J. and Hirota, M. M., 2009. The Brazilian Atlantic Forest: How much is left, and how is the remaining forest distributed? Implications for conservation. Biological Conservation, 142(6), pp. 1141-1153

Roberts, G., 2016. Cassowary on road. [photograph] Available at: http://sunshinecoastbirds.blogspot.co.uk/2016/06/queensland-road-trip-13-etty-bay.html [Accessed: 22/03/17]

Turner, I. M., 1996. Species Loss in Fragments of Tropical Rain Forest: A Review of the Evidence. Journal of Applied Ecology, 33(2), pp. 200-209



Going with the Flow? How ‘friendly’ are Dams really?

Posted on by Elizabeth Henderson

With a growing global population, dams are more relied on than ever to provide electricity and secure land; with over 45,000 >15m tall dams existing globally (World Commision.2005), and mans’ intrusion on biodiversity being a well-known threat (MEA, 2005a), dams may not be as environmentally friendly as they seem.

Dams ultimately obstruct water ways, breaking up continuous systems and causing a number of effects due to their construction (Collier 1996). Like sticking tape across guitar strings; it will still play music, but not to the same extent. They do so in 4 main ways(Ligon 1995):

  • Water flow
  • Sediment
  • Nutrients
  • Energy
  • Biota

 

Water flow is slower upstream due to the build-up of water, which can lead to the creation of reservoirs, an entirely new Ecosystem. The rivers, are more likely to host large plant populations and a different community of organisms (typical of higher order rivers), at much lower orders (Figure.1).
Downstream flow is regulated by the dam itself, and so changes on location. But typically reduce peak flows that provide erosion and creation of sediment downstream (McCartney 2009).

Dams are nutrient and sediment sinks, inhibiting what’s carried downstream. Reducing the flow of all particles to downstream systems, and increasing their build-up in upstream systems, causes different shifts in their Ecosystems. High nutrients upstream puts systems at risk of Eutrophication (a swift increase in phytoplankton blocking sunlight to larger plants, causing substantial loss of oxygen and life), but the loss of material downstream can cause other changes (Figure.2).

The unification of the McKenzie river before (darker blue, 1969) and after (light blue, 1980), which caused in the loss of habitat via islands and sheltered streams, resulting in a 50% decrease in salmonids
The unification of the McKenzie river before (darker blue, 1969) and after (light blue, 1980), which caused in the loss of habitat via islands and sheltered streams, resulting in a 50% decrease in salmonids (Ligon 1995)

Energy includes temperature. Larger reservoirs can become stratified, making specific levels: An upper, warmer, oxygen rich layer and a lower, colder, high nutrient and low-oxygen layer. Dam outflow can come from either of these levels, which effects what occurs downstream. Any change in temperature often puts areas at odds with what it should be for seasonal levels, such as reducing fish growth and plant productivity if lowered (McCartney 2009).

With Biota, fish community migration is the main issue. This mainly refers to the reproduction cycles of migratory fish, such as salmonids, which reproduce in highland areas after migrating upstream. Many dams introduce fish ‘ladders’ in which the fish can ‘jump’ upstream, and others such as the ‘fish cannon’ (see video) or bristle walkways for hagfish. However the main problem is fish can’t typically find the entrance.

Freshwater Ecosystems are more diverse per m2 than both land and marine biomes (MEA 2005b), to sustain this diversity, regional change across the entire river system needs to be present (MEA 2005a). Heavily dammed rivers (e.g. 25), such as the Snake and Columbia Rivers, USA, have ecosystems vastly different from unmodified rivers, causing the loss of its Sockeye and Chinook Salmon (Collier et al 1996). This also causes a similarity of conditions, which increases the risk of invasive species, as they can compete better in ‘more general’ ecosystems (Olden, 2006).

Overall Dams vastly impact river ecosystems, a brief few have been highlighted, but needless to say there are many more, they’re not so ‘friendly’ after all.

.

 

References

Word Count: 499

Collier, M., Webb, R.H. & Schmidt, J.C. (1996) Dams and Rivers: A Primer on the Downstream Effects of Dams

[David] (06, February, 2011) River Continum, Retrieved from URL: http://yorkshiredalesriverstrust.blogspot.co.uk/2011/02/ecology-of-river-changes-as-you-move.html

Ligon, F.K., Dietrich, W.E. & Trush, W.J. (1995) Downstream Ecological Effects of Dams, BioScience, 45(3): 183-192

McCartney, M. (2009) Living with Dams: Managing the Environmental Impacts, Water Policy, 11(1): 121-139

Millenium Ecosystem Assessment (2005a) Ecosystems and Human Well-being: Biodiversity Synthesis, World Resource Institute, Washington, DC

Millenium Ecosystem Assessment (2005b) Ecosystems and Human Well-being: Wetlands and Water Synthesis, World Resource Institute, Washington, DC

Naiman, R.J., Decamps, H. & McClain, H.E. (2005) Riparia: Ecology, Conservation, and Management of Streamside Communities, Elseiver, New York

Olden, J.D., LeRoy Poff, N. & Bestgen, K.R. (2006) Life-History Strategies Predict Fish Invasions and Extirpations in the Colorado River Basin, Ecological Monographs: Ecological Society of America, 76(1): 25-40

[Tech Insider] (2017, 3rd Feburary) Salmon cannon gives fish a boost over dams, Retrieved from: https://www.youtube.com/watch?v=xIB2616zcLk

World Commissions on Dams (2000) Dams and Development: A New Framework for Decision-Making, Earthscan Publications, London