The Badger Cull: Part 1

   The incidence of Tuberculosis (TB) in badgers, the spread to cattle, and the resulting proposed cull of UK badgers has seen huge news coverage and debate in the past year. This story resurfaced after further scientific investigation gave way to a proposed badger hunt, which was postponed as of October this year. The most famous opponent to this cull is Dr Brian May, who has been campaigning to stop what some see as unnecessary killing of native species; and even has his own website to this end.

   The problem lies in the fact that badgers can spread TB to cattle (and vice versa), as the same bacterium causes the disease in both animals; Mycobacterium bovis. Once cattle are infected with TB, they can easily infect other cattle, and so have to be immediately killed; harming agricultural production. To get up-to-date on the matter as it stands, I suggest visiting the BBC Q&A on the topic.

Badgers are still threatened by a possible go-ahead on the proposed
cull to reduce incidences of bovine TB. Source.

   So over the next couple of posts I thought I would look at the scientific papers that provide evidence on whether a badger cull could be effective, and therefore whether it is right that we should seriously harm another species to aid our agriculture.

   

Noc: The Talking Beluga Whale

   I'm sure most people noticed the newspaper articles back in October on the talking beluga whale called Noc. I thought a quick recap of this study was warranted, as The Guardian has named this one of their 'Top 10 wackiest environment stories of 2012'.

A beluga whale filmed wild in Alaska; source.

    This followed the study published in Current Biology by Ridgway et al., 2012, concluding that a beluga whale kept at the National Marine Mammal Foundation in San Diego had learned how to modify sounds to make them more human-like. Apparently this sounded so convincing it fooled a diver into thinking someone had yelled to get out the water; surfacing and calling "who told me to get out?". Ridgway et al., 2012, recorded and analysed these sounds, determining that they were several octaves lower than regular calls, and demonstrate "spontaneous mimicry of the human voice, presumably a result of vocal learning".

Figure 1 from Ridgway et al., 2012, demonstrating acoustic
similarities between human vocalisations (A) and Noc's vocalisations (B).

    The researchers have therefore interpreted Noc's unusual vocalisations as an attempt to mimic humans, due to the presence of human keepers and divers. They found that Noc's vocalisations had an amplitude rhythm similar to human speech (as in figure 1 above); vocal bursts were also similar, averaging around 3 per second.

    Noc has remained vocal, but stopped demonstrating speech-like behaviour after he matured. Vocalisations similar to human speech have also been recorded in white (beluga) whales in the wild, however Ridgway et al., 2012, note that Noc was not a 'good mimic' compared to well-known mimics like parrots. Although it does seem clear that a close association with humans can produce definite behaviour of vocal learning in other species.

A video of the human-like sounds Noc produces.

Critically Endangered Species of the Week: Variable Harlequin Frogs!

About:
    Harlequin Frog (or Clown Frog) actually refers to several species, all of which belong to the genus Atelopus. Atelopus varius, or the Variable Harlequin Frog is listed as critically endangered by the IUCN. All species of Harlequin Frog are named for their bright colours and patterns, and the Variable is usually orange or yellow with dark patches [2]. Individuals of the genus all have bright colouration to warn potential predators of the frog's toxicity [2, 3, 4]; the frogs produce tetrodotoxin, a potent neurotoxin.
    The species is mostly terrestrial, reproducing in water but swimming only rarely and relying on splashes for moisture [2, 4]. They are usually found on rocks or in crevices along streams in humid lowland and montane forests [1, 4]. The frogs eat small arthropods, and its only known predator is a parasitic fly that deposits larvae on the frog's thigh. These then burrow inside and consume the frog from within [2, 4].

The Variable Harlequin Frog, Atelopus varius, showing its
distinctive warning colouration. Photo from [2].

Geographical Range in the wild:
    The Variable Harlequin Frog is critically endangered in both Panama and Costa Rica, and now likely extinct in the former [1, 2, 3]. Atelopus varius now only exists as a single population from one locality in Costa Rica: Fila Chonta, 10km N-W of the city Quepos [1, 4]. 

A map of the geographical range of the Variable Harlequin Frog - the
orange area represents the current range, and the red is the extinct range.
Map from [1].

Number left in existence:
   Around 20-30 years ago the Variable Harlequin Frog was a common species with over 100 populations present in Costa Rica [1]. Since 1988 drastic declines have been reported, with an estimated 80% reduction in numbers with rapid population disappearance. It is likely that no individuals remain in Panama, and very low numbers from one population in Costa Rica [1, 4]. Specific numbers are unknown, but thought to be decreasing, and possibly as low as 60-95 individuals [4].

Why they are endangered:

• The major threat to the species is likely to be Chytridiomycosis, from infestation with Chytrid fungus [1, 2]. This has caused catastrophic declines in other species of the genus, and specimens collected in the past have tested positive for infestation.
• Habitat loss due to human destruction of natural forests [1].
• Predation by introduced trout [1].
• Importantly, the species was collected by the thousands in the 1970s for the international pet trade [1].

What can we do to help?
    Mainly further education and habitat protection, as a captive-breeding programme has been initiated for the Variable Harlequin Frog [1, 4]. The future of the species is still very uncertain, as there appears no legitimate protection of the last known populated habitat. If extinction is to be prevented, this area needs to be better protected from human destruction.


References:
1. http://www.iucnredlist.org/details/54560/0
2. http://animal.discovery.com/tv/vanishing-frogs/top-5/variable-harlequin-frog.html 
3. http://www.endangeredspeciesinternational.org/amphibians5.html
4. http://en.wikipedia.org/wiki/Atelopus_varius

Biodiversity as an Ecosystem Service

    Biodiversity and Ecosystem Services (BES) was a termed coined in the 1990s to describe the essential benefits that ecosystems provide to humanity (e.g. Daily, 1997). This mainly looks at changes to patterns relevant to economic or cultural evaluation, and is important as it can describe the losses humans might face with decreasing biodiversity (Cardinale et al., 2012). Humanity prospers from many ecosystem services, including; diverse and numerous food sources (plants and animals), pharmaceutical products, waste decomposition and recycling, and cultural inspiration. In many cases biodiversity has been considered so important to human culture, and having such a large impact, that it has been itself called an ecosystem service (Mace, Norris and Fitter, 2012).

    This means that biodiversity is often viewed as an underlying factor driving ecosystem services; usually in this case the presence/absence of entire habitats or organism groups. A good example of this is that high biodiversity is required for the maintenance of mangrove forests, and these are important for local human settlements as flood protection (Cardinale et al., 2012).

A diagram produced by Cardinale et al., 2012, summarising several
 hundred studies. This shows the great effect biodiversity
has on increasing ecosystem services.

    Cardinale et al., 2012, reviews past papers on biodiversity loss and the effects this has on ecosystems - they find several consensus points on these effects, from a high number of studies. These include:

1. Analyses published since 2005 have shown that, as a general rule, reductions in the diversity of genes, species and groups of organisms reduces the efficiency by which whole communities capture essential resources (nutrients, light, water or prey; e.g. Cardinale et al., 2011; Worm et al., 2006). This actually seems very consistent across different groups, trophic levels and ecosystems (Cardinale et al., 2012). 
2. There is mounting evidence that high biodiversity increases the stability of ecosystem functions through time; for example total resource capture and biomass production are more stable in a diverse community (e.g. in Hector et al., 2010). However it is not known that biodiversity enhances all form of community stability, and has not yet been looked at in a more encompassing light (Ives and Carpenter, 2007).
3. Diverse communities (high biodiversity) are more productive as they contain key species with a large influence and differences in functional traits. This higher productivity is extremely important for human resource utilisation. However the actual extent to which some of these influences broadly contribute to ecosystem function has yet to be confirmed.
4. Functional traits of organisms have large impacts on the magnitude of ecosystem functions - this means that different traits are lost in extinctions, and this causes fluctuations in ecosystem functions. I.e. if a highly productive species, important to the ecosystem (and to humans as a resource), is lost then reductions in ecological process may follow (which can have negative impacts on human civilisations). However there is considerable variation in the impacts loss of particular traits can have on an ecosystem, and so we must know great detail about the species at risk of extinction and the possible effects of this to predict any consequences accurately (Suding et al., 2008).

    Several other consensus points on the effects of biodiversity on ecosystems and their services are also explored in Cardinale et al., 2012, demonstrating the large impact species loss can have. As ecosystem services can be extremely important to human culture and civilisation, and biodiversity underlies many of these services, maintenance of species number is of clear significance to humanity.

Critically Endangered Species of the Week: the Jamaican Iguana!

About:

    The Jamaican Iguana (Jamaican Ground Iguana, Jamaican Rock Iguana), Cyclura collei, is believed to be one of the most endangered lizard species at present [1]. The Iguanas are large and heavy-bodied, often green to blueish in colour, with darker olive-green colouration on the shoulders [3, 4]. Three dark chevrons can be seen along the animal's back, and the crest scales found here are often lighter in colour than the body [3, 4]. 
    Male Jamaican Iguanas  grow to almost 17 inches in length, and females usually to almost 15 inches [3]. The species shows small amounts of sexual dimorphism, as the dorsal crests of the males grow higher.
   The species is primarily herbivorous, consuming a diverse range (over 100 species) of leaves, flowers and fruits [3].

The Jamaican Iguana, Cyclura collei, likely has a remaining
population of less than 100 individuals. Picture from [2].

Number left in existence:

    Surveys of previous ranges have revealed the Jamaican Iguana is extinct in all areas aside from the Hellshire Hills [3]. A preliminary study in 1990 revealed a population of under 100 individuals, but found minimal juvenile recruitment [1]. The population in the area does appear to be increasing due to reintroduction and predator control, however it is unknown how protected any individuals straying out of this area are.

Geographical Range in the wild:

The small remaining geographical range of the Jamaican
Iguana - a <10km squared range in the Hellshire Hills.

    The species is only known to exist in the extremely limited area of the Hellshire Hills, Jamaica [1, 3, 4]. Despite having a larger, suitable, range available in this area, the Iguanas are only found in the central core area protected from Indian Mongoose [4]. This gives a range of <10 square kilometres; research has failed to locate any individuals further afield than this [1]. This is much smaller than their widespread historical range in the 19th century.

Why they are endangered:

• A main reason for their decline is high levels of predation by introduced species; the massive population decline in the 19th century is partially attributed to the introduction of the Indian Mongoose [1, 4], and these have been found to prey on young iguanas and eggs at present. Introduction of dogs for pig hunting, cats and feral pigs has also harmed populations [1].
• Habitat destruction; their small habitat is being increasingly degraded by human encroachment from the edges [1].
• Extensive logging for charcoal production by humans has destroyed much of their suitable habitat [1]. This tree-cutting is illegal.

What can we do to help?

    The central core area of the Hellshire Hills is now under extensive predator control, and mature Iguanas are being reintroducted; together this means the population in this area is increasing. The Hellshire Hills area is also protected by law under the Forest Act of 1996, however this has received little enforcement [1]. A conservation group specific to the species also captures, rears and releases the Iguanas, giving them a 'kick-start' [4]. 
    The Iguanas main need now is translocation to predator-free islands (which obviously requires a lot of resources in moving the animals, and in locating and maintaining the islands as refuges), and further prevention of deforestation in their current range and these new areas. Translocation is highly important, as threatening development projects have been proposed for the Hellshire Hill area, including large-scale limestone mining, human settlements and tourism [1].

References:

1. http://www.iucnredlist.org/details/6027/0
2. http://bushwarriors.org/2011/07/26/iucn-species-of-the-day-jamaican-iguana/
3. http://en.wikipedia.org/wiki/Jamaican_iguana
4. http://www.iguanafoundation.org/s17-118-Jamaican-Iguana.aspx

Management of Ecosystems With Fire

   Controlled fires are very often used as a way to maintain the complexity, and therefore plant biodiversity, of a number of managed areas, such as grassland and forests. Appropriate burning practices can be extremely significant in preventing full succession to low diversity tree systems, and maintaining high numbers of habitats, along with other methods (see checklists created for this purpose by Lindenmayer, Franklin and Fischer, 2006). Menke, 1992, noted how prescribed burning can reduce alien annual plant seed production, increase diversity of smaller plants as competition for resources is removed, and increase long-term native seed establishment. It could be thought that this would result in increasing number of habitats for small animals such as insects (as long as the burning is controlled).

Prescribed burning of grassland to increase fertility, and decrease
competition for establishing plant species; source.

   However, I wanted to highlight a paper that is set to be published in February 2013 by Little, Hockey and Jansen, who looked at the impact of controlled burning on South African grassland bird and arthropod (such as insects) diversity. By studying eight sights of varying fire frequency over two summer seasons found that both of these assemblages reflected the immediate habitat disturbance of the fires in changing ways (depending on season and management practices). Fires particularly affected grassland-breeding birds, as areas were burnt in the territory-forming stage of the breeding cycle. Of 10 arthropod orders investigated in the area, only one responded positively to burning (that containing grasshoppers). Coleman and Rieske, 2006, also found arthropod abundance in oak-pine forests was devastated by burning, and took at least two growing seasons to begin recovery.

   I think studies such as this show that while controlled burning is becoming a popular method of reducing low diversity tree systems, and reestablishing native and rarer plant species, it can have dramatic affects on animal systems, even causing huge drops in abundances. This shows that it is necessary to investigate the effects of burning in particular areas before this is used to maintain ecosystems.

Critically Endangered Species of the Week: the Spoon-billed Sandpiper!

About:
    The Spoon-billed Sandpiper, Eurynorhynchus pygmeus, is one of the world's most endangered birds [2]. They are small, wading birds, individuals only averaging 14-16cm in length [5]. Breeding adults have a red-brown head, neck and breast with dark brown streaks, pale black-brown-grey wings and white underparts [3]. Non-breeding adults lack the reddish colouration.
    The species has a very specialised breeding habitat; they use only lagoon spits with adjacent estuary or mudflat habitats for feeding during nesting [1, 3]. They feed by pecking and probing in the sand and water, and use their bill as a shovel [1, 3]; for this reason they have a bill that is unusually spatulate, or spoon-shaped [3, 5].

The Spoon-billed Sandpiper, Erynorhynchus pygmeus, 
showing the distinctive spatulate bill shape.

Number left in existence:
    The species has an already extremely low population size, and has been found to be undergoing a dramatic rate of decline; 2,00-2,800 breeding pairs were estimated in the 1970s, to fewer than 150-320 in 2008 [1, 2, 3]. The breeding population in 2009-2010 was optimistically estimated to be 120-200 pairs, equating to 240-400 mature individuals, and 360-600 individuals total (although is likely less than this) [1].

Geographical Range in the wild:
     Spoon-billed Sandpipers have a naturally limited breeding range on the Chukotsk peninsula and up to the isthmus of the Kamchatka peninsula, in north-eastern Russia [1, 2, 3, 5]. The birds migrate down the western Pacific coast through Russia, Japan, North and South Korea, China, Hong Kong, Taiwan and Vietnam [1, 3]. They mainly overwinter in Bangladesh and Myanmar [1, 3].
   Overwintering and breeding occur at specific sites year on year, and breeding takes place in extremely specialised habitats, almost always within 5km of the sea shore [1].

Why they are endangered:

• The tidal flats that form the migratory and wintering habitats are being reclaimed for industry, infrastructure and aquaculture. These areas are also becoming increasingly polluted by human activity [1, 3].
• The birds are regularly caught in nets set to catch other waders for food in the main wintering areas of Myanmar and Bangladesh [1, 5]. Immature birds are particularly exposed to capture as they spend more time in non-breeding areas, harming recruitment of the species [5].
• Nests in the vicinity of villages are sometimes destroyed by dogs [1]. Additionally, human disturbance (residents and researchers) may have caused increased levels of nest desertion [1, 3].

What can we do to help?
    Some breeding and wintering areas are already protected, however lobbying is required to establish more protected zones. Researchers and local environmental groups have been educating villages in the geographical ranges, encouraging them to agree to a hunting ban on the species and to respect them [1, 2]. Additionally a captive-rearing and breeding programme started in 2011, taking place in the UK - this has seen some success, as fourteen Spoon-billed Sandpipers were hatched this year [see video; 4, 2, 5].

Some of the few Spoon-billed Sandpipers hatched in captivity,

at the Slimbridge wetland centre in Gloucestershire [4].

    Research and monitoring of population numbers at known breeding sites is still very much a necessity, and searches for suitable habitat in North Kamchatka is also important [1]. However scientific research needs to be more strictly controlled, with no egg or bird collection or nest disturbance for any reason. The species would greatly benefit from a stopping of hunting in key sites in Myanmar, Bangladesh and Russia, and needs legal protection passed [1].

References:
1. http://www.iucnredlist.org/details/106003060/0
2. http://www.saving-spoon-billed-sandpiper.com/
3. http://www.birdlife.org/datazone/speciesfactsheet.php?id=3060
4. http://www.guardian.co.uk/environment/2012/jul/13/spoon-billed-sandpiper-chicks-hatch
5. http://www.wwt.org.uk/conservation/saving-wildlife/science-and-action/globally-threatened-species/spoon-billed-sandpiper

Eutrophication: Once Happened, Can We Reverse It?

    So what happens if no methods are put in place to prevent eutrophication, or the measures fail, and the water body becomes algae-dominated and turbid? Can the eutrophication and associated impacts be reversed? And can this result in a recovery of water bodies and their ecosystems? Without getting too far into complicated details, some studies on lakes damaged by eutrophication have found a simple diversion of nutrient sources away from water bodies has helped recovery; for example Lake Washington (Edmondson, 1980). However waste pipe diversions took place before extreme effects of eutrophication had materialised.

Lake Washington.

    Contrastingly, a great deal of longer-term research demonstrates that once a threshold is crossed, a 'tipping point', which pushes the system into the low biodiversity, turbid state, there are many factors which prevent recovery to clear water (Kumagai and Vincent, 2003). Occasionally this is due to an insufficient reduction in nutrient levels, i.e. failure to stop agricultural run-off or sewage from reaching the water body. 
  
    However, usually systems appear to recover in tests such as those above, but additional factors later cause a move back to turbid water, even without the addition of more nutrients by humans. For example, leaving piscivorous fish in a recovering water body can cause (smaller) planktivorous fish populations to remain low, leading to decreased predation of algae and returning algal blooms (Kumagai and Vincent, 2003). Fish such as pike (often introduced into lakes by humans) also have to be removed for efficient recovery, as these disturb sediments, increasing turbidity and releasing stored nutrients, making it more difficult for plant communities to recover (Kumagai and Vincent, 2003). 

    Additionally, Sondergaard et al., 1996, demonstrated that grazing waterfowl (such as swans) can prevent lakes recovering after eutrophication. Birds were found to suppress the regrowth of plants in these lakes (required for the return from a turbid water state), negatively impacting water quality; many hypertrophic areas therefore also require enclosures protecting them from grazing. Gulati, 1995,  notes that many lakes have returned to a turbid state as recovery has only focused on reducing the amount of nutrients entering the water; biomanipulation such as the above is generally found to be necessary if water bodies are to improve after eutrophication. A classic case of this is the Norfolk Broads (such as Barton Broad), which has suffered chronic eutrophication, and required huge amounts of additional aid in the form of biomanipulation to even recover small areas.

    Because so many factors are involved in water body recovery, truly reversing eutrophication becomes basically unfeasible - these all need to be continually maintained, and how can we act on all these issues with limited monetary resources?

Eutrophication: Prevention Methods

    Having thought about the consequences of eutrophication, we might now think 'do methods exist to prevent this?' Now the best way to reduce this nutrient-load on water bodies would be to stop having agricultural areas and settlements near them - obviously this is completely unfeasible and never going to happen. However there are several measures that can be put in place to maintain the health of our water bodies, without severely impacting our way of life:

• Riparian Buffers: These are vegetated areas between a river and adjacent areas of land use, and are a widely used method for removing pollutants (like the excess nutrients in eutrophication) from agricultural areas. This means less surface run-off meets a stream/river, leading to less nutrients being deposited at their mouth (e.g. in a lake or sea), and some prevention of eutrophication. Lee, Isenhart and Schultz (2003) found a combined species buffer zone can remove between 80-97% of the nitrogen and phosphorous run-off. However different species have been found to contribute different rates of absorption to a buffer zone (Haycock and Pinay, 1993). Older forests have also been shown to be much less efficient at trapping N and P than younger forests (Mander et al., 1997).

A Riparian Buffer zone either side of a stream in Iowa.

• Maintenance of river floodplains: Maintaining flat plains adjacent to rivers can also help to reduce nutrient-load in mouth water bodies; as when the river breaks its banks and floods, sediments and nutrients are deposited on the plains either side of the river. Tockner et al., 2002, found of a river-floodplain system in Switzerland that the floodplain served as a major sink of phosphorus and suspended matter, and was never a source for organic nutrients. However quantification of their use in preventing eutrophication does vary; Tockner et al., 1999, found of a system in Austria that the floodplain did serve as a sink for sediments and nitrates, but was actually a source for dissolved organic carbon and algal biomass.

A river floodplain on the Isle of Wight.

• Meandering: Having a wide and straight river causes the water to flow faster, preventing sediments and nutrients from being deposited on the banks and bottom, and reaching larger water bodies as nutrient-rich. Introducing meanders to rivers slows the water flow, and causes more nutrients to be deposited on the bends; reducing eutrophication in end water bodies.

Meanders of the Rio Cauto in Cuba.

• Divertion of waste pipes: A fairly obvious measure, sewage pipes that offload into water bodies should be diverted away from areas in danger of eutrophication. Alternatively, wastewater can be treated to reduce the amount of nutrients carried into water bodies. This can dramatically decrease incidences of eutrophication, as anthropogenic waste is one of the widest known causes for destruction of lake ecosystems (Sreenivasan, 1969).

   These are all ways in which we can fairly easily reduce anthropogenic pollution and associated eutrophication of water bodies. While methods such as re-meandering and creation of floodplains may have high monetary costs and require maintenance, these are still preferable to the difficult, time-consuming, and often impossible process of recovering systems damaged by unnatural eutrophication.

Critically Endangered Species of the Week: the Pygmy Three-toed Sloth!

The Pygmy Three-toed Sloth, Bradypus pygmaeus. Picture source.

About:
    The Pygmy Three-toed Sloth, Bradypus pygmaeus, the smallest of all sloths, was only described as a separate species in 2011 [1,2,3]. The species likely evolved as a result of Island/Insular Dwarfism (e.g. Lomolino, 1985), due to the isolation of individuals of a mainland Panama population of Brown-throated Three-toed Sloths [2].
   The sloths have a tan-coloured face, with a dark band across the brow and usually orange eye patches. The back is often dark brown with a dorsal stripe. They also have long hairs on the sides of the head, giving the impression of a hood [2,3,4]. Individuals tend to weigh 2.5-3.5kg, and measure 48-53cm on average [2].
   Like all other three-toed sloths, they are arboreal mammals that feed on leaves. Uniquely, the Pygmy Three-toad Sloth is found exclusively in red mangroves, and feed on coarse leaves [2,4]. Again like other sloths their coats may appear green-tinged, due to the growing algae that serves as camoflage [2,3,4].

The Pygmy Three-toed Sloth, Bradypus pygmaeus. Picture source.

Number left in existence:
    Little is known of remaining population numbers, however it is estimated that the population consists of less than 500 individuals, and is declining [1,5]. Other estimates of 300, or 200 individuals have been proposed [5].


The small orange area shows the geographical range
of the Pygmy Three-toed sloth; Isla Escudo De Veraguas.

Geographical Range in the wild:   The Pygmy Three-toed Sloth is endemic to Isla Escudo de Veraguas, in the islands of Bocas del Toro, off the coast of Panama [1,2,3,4]. This gives the species a very isolated, restricted range of only around 4.3km squared [1]. Furthermore, the sloths have only been located in the red mangroves of the island, giving a range of 1.3-1.5km squared [1,4].

Why are they endangered:

• The island is thankfully uninhabited, however seasonal visitors (e.g. fishermen and local people) are known to hunt the sloths opportunistically [1,3].
• Studies such as Silva et al., 2010, suggest the species has a low level of genetic diversity, which may harm chances of survival if the population decreases any further [1].
• Indigenous people have been illegally cutting down the mangroves, reducing the available habitat and food for these sloths [1,3,4].
• Being so isolated, the species cannot disperse to other areas when under pressure from destruction of habitat and hunting [2].

What can we do to help?
    Thankfully Isla Escudo de Veraguas is protected as a wildlife refuge, contained within the Comarca Indigenous Reserve [1,4]. However much stricter enforcement of this protection is drastically required - the area receives little attention from wildlife protection authorities, as evidenced by the continued felling of the red mangroves [1,2]. Local awareness programmes are always required to encourage conservation of the species.

                           A video by ZSL EDGE, on their attempts to conserve the Pygmy Three-toed Sloth.

References:
1. http://www.iucnredlist.org/details/61925/0
2. http://en.wikipedia.org/wiki/Pygmy_Three-toed_Sloth
3. http://www.arkive.org/pygmy-three-toed-sloth/bradypus-pygmaeus/
4. http://www.edgeofexistence.org/mammals/species_info.php?id=1396
5. https://www.zsl.org/conservation/news/in-search-of-the-pygmy-sloth,960,NS.html
6. http://www.guardian.co.uk/environment/gallery/2012/sep/11/most-endangered-species-in-pictures#/?picture=395933529&index=1 

Eutrophication: Effects

    Eutrophication (or hypertrophication) is the response of an ecosystem to the addition of artificial or natural resources to an aquatic system. The most common mode of eutrophication is the enrichment or fertilisation of water bodies with nitrogen (N) and phosphorus (P). As these are extremely important limiting factors for life, due to their inclusion in amino acids (to build proteins), high levels of eutrophication can cause disastrous consequences to an ecosystem.

   These nutrients are present in low concentrations in pristine water bodies to support life, however when the water becomes in enriched in N and P this can cause problems for the ecosystem and health of the area. The rough order of effects goes as follows:

1. Water bodies become unnaturally enriched in N and P (usually).
2. Unnaturally high rates of plant production (primary) result, as these nutrients are no longer limiting their growth. It is normally surface plants and particular types of algae that grow rapidly.
3. This results in algal surface blooms, preventing the sunlight from penetrating the water.
4. Plants beneath the surface cannot photosynthesis, die and are decomposed (mainly by bacteria).
5. The increased action by decomposers causes oxygen depletion from the water.
6. Lack of oxygen (and sometimes blooms of toxic species of algae) often cause the death of benthic organisms (e.g. invertebrates) and fish.
7. This ultimately results in a turbid, harsh system with low biodiversity - lacking in fish, multicelled plants and invertebrates, and algae-dominated. This gives the look of a 'green soup', which can be seen below.

Hungabee Lake (left), Canada; a healthy lake system. Lake Taihu (right)
is a highly turbid, algae-dominated lake resulting from eutrophication.

   Eutrophication does take place as a natural process as sediments and organic matter accumulate. However, anthropogenic influences cause this to happen in a much more rapid timescale - the main source of nutrient flow into water bodies is nearby human settlements. Direct flows are increasingly common, taking the form of agricultural run-off from farm fertilisation and waste pipes. Increasing atmospheric pollution is even causing eutrophication in lakes at a great distance from any humans. 

   Currently this seems yet another way in which human utilisation of resources is damaging the environment and harming biodiversity, and many studies have been undertaken into the attempted recovery of these systems. The methods in which this has been attempted, and whether we even can repair the damage done will follow...