Land Reclamation

Welcome back, I'm assuming you're here for more porpoise and dolphin pics? Ok, but not until we've explored some of our impacts on their marine environment!

The  population, commercial and industrial expansion of Hong Kong, particularly over the last 60 years, has resulted in a degradation of its coastline and marine environment. Perhaps the most notable activity that has caused this degradation is Land Reclamation.

As we identified early on in this blog, Hong Kong possesses a huge, expanding population that is requiring more and more land in order to live, work and survive. To fulfil this demand Hong Kong has frequently utilised land reclamation techniques.

What?

Simply put, it is the building up of the sea bed to create an above sea-level surface that is stable enough for further construction or other development. There are various methods used for achieving this build up but broadly speaking they involve the replacement of the soft silt sediments on the seabed with large deposits of rocks (Yan et al, 2013).

When?

The earliest reports of land reclamation in China originated from the Western Han Dynasty where coastal areas were reclaimed in order to create terraces for the recovery of salt from sea water.
Modern reclamation, as we would consider it (i.e. the creation of land for industry etc), began in Hong Kong during the mid 19th Century (Jiao, 2000) shortly after the beginning of the British occupation. Large areas of marshland close to the harbour were bought and reclaimed by traders wishing to create easy access to the harbour.

Since those initial projects, land reclamation has been undertaken on much larger scales culminating in an estimated 10% increase in land surface across Hong Kong by 2000. Furthermore, this increase is due to accelerate with the recent commencement of several larger scale industrial projects (Jiao et al, 2000). The graphic below gives an impression of how reclamation projects have advanced from their humble beginnings and have predominantly been focused on both sides of Victoria harbour with more recent undertakings towards the western edges of Lantau and the New territories.

Estimates of the evolution of land reclamation across Hong Kong, courtesy of www.scmp.com

Where?

Two of the most recent reclamation projects carried out (and in fact still being carried) in Hong Kong are the construction of the HK International Airport and the construction of the Macau-Zhuhai-Hong Kong Bridge:

Hong Kong International Airport

Take another quick look at our 'evolution of land reclamation' graphic; you see the huge area on the northern edge of Lantau? That's the site of Hong Kong's newest airport and home to over 12km^2 of reclaimed land, Hong Kong's largest, completed reclamation project so far (Plant et al, 1998).

If you're desperate for a little more on reclamation methods here's a link for a promo video released on Hong Kong International airports offical youtube channel, I won't embed the video because its seriously cheesy and saccharine with the positive (marketing) aspects of reclamation, but it does offer a brief synopsis of the reclamation project: HK Airport Reclamation.

Hong Kong - Zhuhai - Macau Bridge (HZMB)

A little further west from the airport is the bridge project which aims to be the first step in connecting three of the largest population centres of the Pearl River Delta (China's industrial centre) through a combination of bridge and tunnel networks. A large portion of this project is the creation of a series of new islands.

Preparatory construction work for the bridge commenced in late 2009 and has a predicted completion data of 2016  (ARUP website, 2010) .

Route of the New bridge, courtesy of www.NCE.co.uk

Impacts

It seems logical that the deposition of 1000s of tons of material into a coastal area is perhaps one of the most powerful impacts to which we could subject a marine environment.  Jefferson et al, (2009) created an informal hierarchy of  'development activities' associated with the industrialisation of Hong Kong and their respective impacts on the marine environment which placed land reclamation at the top of the list.

Those of you who tuned in last week may also notice that these two examples are placed, at least partially, within the same zone that the WWF Hong Kong identified as containing White Dolphin populations. Hung et al (2004) confirm that the ranging area of the dolphin populations identified across the Pearl River Estuary extend across western Hong Kong waters, although they go on to state that further investigation of true numbers are required. Regardless, it is clear that the reclamation being undertaken for these projects will have an impact upon these local cetacean populations.

Aside from the complete removal of swathes of environment, there are additional impacts relating to the upcast sediments and potential contaminants sealed within these deposits. Yan et al (2013) provide a case study for the future off-shore airport at Jinzhou Bay that models the impacts of two reclamation methods: Underwater Explosion and Silt dredging.

• As the name implies the 'Underwater Explosion' method of soft silt removal is through the explosion of Trinitrotoluene (TNT) packages that are placed deep within the sediments. The explosion leaves the sediment, and any previously sealed contaminants suspended in the water allowing rock deposits, that were previously dumped on top of the sediment, to enter the newly cleared area. This method can have two catastrophic effects on marine ecology: the primary explosion can disorientate, or even kill marine life, particularly those that possess carefully balanced swim-bladders (Jefferson et al, 2009), within a given radius whilst the dense spread of suspended sediment can extend across huge areas destroying the ability of phytoplankton to photosynthesise and negatively affecting zooplankton growth (Yan et al, 2013).

• The 'Silt Dredging' method involves the construction of dredgers which suck up the silt and deposit it elsewhere. This method lacks the severe impact of the former, but possesses the same risk of disturbing contaminated sediments whilst also requiring an additional area for dumping of the extracted deposits.

A quick aside: for any Environmental Modelling MSc people out there I really recommend having a look over the case study I mentioned earlier (Yan et al, 2013). It's a good example of a modern project involving comparisons, predictions and evaluations through model application and is the kind of work that any of us may be involved with in the future.

And now, as promised....porpoises!

D'AAAAAW!!!! courtesy of www.china.org.cn

Won't somebody please think of the porpoises???

This post marks the introduction of a new theme here at standing-room-only: Impacts on Marine Ecology.

The 263 islands forming Hong Kong boast an incredible 733km of coastline leading to the expanse of the South China Sea. This setting provides an multitude of habitats for various marine fauna. WWF Hong Kong provides a great synopsis of marine biodiversity across the islands.

Perhaps the most noteworthy members of HK's marine ecology are the Chinese White Dolphin (Sousa chinensis) and the Finless Porpoise (Neophocaena phocaenoides). Whilst a total of 16 Cetacea species (Wikipedia) have been recorded in Hong Kong waters the White Dolphin and Finless Porpoise are the only members of this group that are spotted with enough frequency to be considered local species (Jefferson et al, 2009).

The Finless Porpoise, courtesy of the WWF.

• The Finless Porpoise is highly distinctive due to it lack of a dorsal fin (bet you didn't see that coming?), a unique trait amongst porpoises.

A distribution study carried out by Jefferson et al, 2002 observed that in the Hong Kong area the porpoises are limited to the southern and south-eastern waters and appear to traverse this area on a seasonal basis. It is thought that the porpoises' aversion to freshwater prevents their movement from straying further west where the freshwater outflow from the Pearl River Delta has a stronger influence on local salinity levels.  The study also notes that coastal areas with seasonally increased freshwater input (Southern Lantau island for example) cause the populations to avoid the area until salinity levels are recovered.

Between 1995 and 2000 the same study recorded that the abundance of the mammals in the HK area varied seasonally from approximately 55 observed members in autumn to over 150 in spring-time. It is thought that this fluctuation is caused by porpoise groups moving north-east into Chinese waters during the summer.

Chinese white dolphin, courtesy of actionasia.com

• The Chinese White Dolphin (also known as the Indo-Pacific Humpback Dolphin) has a light pink skin, a result of blood vessels close to the skin surface that are used to regulate the internal temperature of the mammal.

The White Dolphin appear to be the antithesis of the Finless Porpoise in regards to preferred habitat: they are present across all of Hong Kong's western waters and are rarely observed in HK's central-southern or south-eastern waters. The dolphin population is also known to extend north from western Hong Kong, following the freshwater influence of the Pearl River Estuary (Jefferson et al, 2009).

Further studies by the, now ubiquitous, Jefferson and Hung, 2004 recorded that although dolphin numbers in, and adjacent to, Hong Kong waters varied between 103 in spring to 193 in autumn, these variations were not reflected in the overall population. This suggests that, unlike the Finless Porpoise, the White Dolphin is a year round resident of HK waters.

The two species are known to coincide in just one area: the Soko Islands. Which may account for the recent government proposed plans to create a new marine park in the vicinity (Hong Kong Government, 2014).

Soko Islands (image courtesy of South China Morning Post). Read article here.

It is widely accepted that Hong Kong's marine ecology has suffered massive deterioration and is potentially on the verge of collapse (WWF website). The impact of large scale development across Hong Kong and China is negatively affecting, and in some cases completely obliterating the habitat for Cetaceans. Join me next time when we take a look at these impacts and how they are affecting the marine ecology.

Can't get enough Porpoises!

Agriculture 2 - Nitrogen: too much of a good thing?

Last time on Standing Room Only....

• Due to its lack of adequate arable land Hong Kong relies upon imports from China for 90% of its fresh food.
• Annually increasing applications of nitrogen chemical fertilisers (CF-N) allow China to supply not only its world leading population but export the excess to Hong Kong and numerous other countries.
• Of late China accounts for 30% of the worlds yearly total Nitrogen fertilisers (CF-N's) used.

and now Part 2...

Clearly using larger and larger amounts of CF-N can result in higher yields being produced more quickly and therefore enable multiple crop cycles within a time frame that previously would have only allowed a single harvest. 

The downside is that the efficiency of the fertilisers decreases substantially when greater volumes are applied: physical factors such as the proportion of nitrogen that a soil can retain and the methods used to apply the fertiliser place hard limits on how much nitrogen (N) is actually utilised by the plants. Perhaps it's a little easier to explain this by thinking in terms of a 'nitrogen balance' within a soil:

Known input of CF-N = N present within harvested crop + Unaccounted N. 

This unaccounted N is 'lost' through the crop process in a variety of manners,  Zhu and Chen, 2002 provide a great quantitative assessment of how this 'Unaccounted N' is distributed, although it's a little dry if you're not into numerous statistical comparisons etc. so here's my take on it:

• Up to a third of the applied N is retained in the soil. This proportion is dependent upon crop type, irrigation and the history of N application (longer periods of fertiliser use result in greater accumulation of N). Potentially this retained nitrogen can be used up by the next crop cycle but only if the N remains in the root zone.
• Potentially a fifth of the CF-N can leach out of the root-zone (again this is highly dependent upon soil type, depths, irrigation etc). Predominantly this leaching occurs during the crops' initial growing process when there is a lot of water flowing through the ground but the plants have not developed sufficiently to use the majority of the fertiliser. 
• A small amount of the excess nitrogen can be lost due to above ground run-off. As with leaching this generally occurs early on in the crop cycle, flooding or excess irrigation carries nitrogen rich silts away from the crop-land and into local watercourses.
• The primary cause of nitrogen loss is denitrification and may account for up to a massive 50% of unaccounted nitrogen. Dentrification refers to the the microbial reduction of CF-N producing gaseous emissions which are subsequently lost to the atmosphere.

Visual representation of the nitrogen balance courtesy of the FAO.

So, we know that the application of increasing quantities of CF-N can lead to larger quantities of N escaping the agricultural system and reaching the natural environment. Now we need to consider what are the effects of dumping an excess of nitrogen into a carefully balanced ecosystem?

We've seen that the unaccounted N is basically transported in two ways: hydrologically (leaching and run-off) and through gaseous emission (denitrification). 

Hydrologically lost CF-N have an incredibly high chance of reaching local water systems where they can cause large scale contamination.  This form of contamination is so common and wide spread that the World Health Organisation denotes agricultural application of nitrogen as a primary cause for nitrate water pollution (WHO, 2011). They go on to state that drinking water sourced from agricultural areas often exceeds 50mg/l (that's 5 times the level generally observed from drinking water derived from surface water in non agricultural areas). 

Nitrogen that finds its way into lake systems also leads to a substantial increase in 'Algae Blooms'. The eutrophication of algae has a hugely destructive effect on lake ecology and is potentially irreversible in some cases (Carpenter et al, 1999).

Chemical fertilisers (including CF-N) causing eutrophication and its resultant impact on lake ecology. Courtesy of sciencebitz.

The major emissions resulting from microbial reduction of CF-N (denitrification) are nitric oxide (NO), nitrous oxide (N2O) and di-nitrogen (N2) (Zhang et al, 2009).  Perhaps the most important of these to consider within the scope of this blog is nitrous oxide. Emissions of N2O are a major contribution to the greenhouse effect (which is widely documented so let's not dive into its intricacies at the moment) Wikipedia. Although agriculturally derived quantities of nitrous oxide are currently considered to be relatively low (around 0.2kg N/ha./year) the amount is increasing each year (Kim et al, 2007). More importantly the IPCC has predicted that N2O has nearly 300 times the global warming potential of CO2 over the next 100 years!

OK, I feel that we've identified that we have the ability to drastically enhance a soil's naturally sustainable output to a level that can cope with the demands of an ever increasing population. We've also determined that this prolific productivity comes with a price: two significant impacts upon the environment. Let's put a pin in agriculture for now so that next time we can explore some other environmental impacts caused by an increasing population.

Even Paul Walker and Vin Diesel are obsessed with NOS (Nitrous oxide for the uninitiated)!

P.S....

If you fancy a bit of further reading Gruber and Galloway, 2008 have an informative and accessible article in 'Nature' that explains some more of the nitrogen cycle. I strongly recommend checking it out.