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.

Agriculture Part 1

Hi, welcome back.

Last time I, hopefully, gave you an impression of where this blog would take us as well as a few facts and figures to get us rolling. Today I’d like to introduce my first theme in environmental impacts of an increasing human population…..AGRICULTURE.

Hong Kong has a total area of approximately 1100km² consisting of Hong Kong Island, Kowloon Peninsula and the New Territories (including Lantau Island and over 260 smaller islands). The Hong Kong Government estimate that only a quarter of the total area represents ‘developed’ land and it is within this 275km² that the majority of Hong Kong’s 7.2 million strong population live and work.

A false-colour satellite image of Hong Kong depicting developed (pink) and natural (green) landscapes (Courtesy of Wikipedia, annotated by the author).

Clearly the areas of ‘developed land’ are predominantly highly urbanised or industrialised in order to accommodate the local population. Unfortunately outside of this area Hong Kong’s geography mainly comprises mountainous topography that prevents the development of large scale agricultural activity. It is estimated that at the beginning of 2014 there was only 7km² of active farmland in the whole region! (Hong Kong Government, 2014).

So how do they pick up the slack? They look to the north...CHINA! According to the HK Food and Health Bureau 90% of their fresh food is sourced directly from China.

Currently, and historically, China possesses the world’s largest population with 1.3 Billion people in 2013 (you guessed it: World Bank). However, as of 1998 the country only had 0.1 Hectares of arable land per person - that's less than half the world average at the time (Zhu and Chen, 2002). Given their population and low percentage of arable land how do they produce enough to subsist? Let alone have an excess with which to help out other countries?

Well, a major aspect of the country’s high productivity from a limited area is due to the introduction of Nitrogen based chemical fertilisers (CF-N) (Wikipedia). After the Second World War the application of these fertilisers allowed China’s overall food production to increase by over 450% in 50 years (1950-2000) (Chinese Agriculture Yearbook 1980-1999 cited in Zhu and Chen, 2002). This massive growth was achieved in spite of an overall decrease in the total arable area of the country, predominantly due to increasing levels of construction and industrialisation (People's Republic of China Government website).

There we have it: a clear example of an increasing population placing a severe impact on an environment. Complete with an anthropogenic solution of chemically altering the environment in order to inflate its naturally sustainable production level.

However, there are a couple of sides to this story that we have not yet covered: Firstly is the fact that achieving this immense output is requiring higher and higher applications of CF-N's each year. For a little context (by now I hope you realise that this means ‘here are some numbers’) these yearly increases mean that in 1998 China used 30% of the total Nitrogen fertilisers used in the world (Zhu and Chen, 2002).

Ok, that seems like a good place for a cliff-hanger. I’ll get another post up over the next few days where we can further this analysis and have a look at the impact that this massively increased quantity of Nitrogen is having on the natural environment and what steps could/can be taken to mitigate its effects.  Much like Stallone’s chef d'œuvre it’s sure to be a post filled with thrills.