The sleepy coastal village of Fish Hoek has been periodically rudely awoken by the increased spate in shark sightings and indeed, attacks. This rampant increase is largely attributed to chumming by shark tour operators, an increased swimmer populace or the over-fished state of our seas. This controversy has fuelled many a heated fireside debate and has tendency to ignite passionate argument even between close friends. The role that global climate change plays in forcing shark behavioural changes is commonly overlooked and with the upcoming COP17 summit to be held in Durban next month, it is perhaps time that this external factor is paid more due attention.


Catch phrases like “global warming” and “global climate change” are often tossed, almost carelessly, around in the media. With COP17 mere days away we are likely to see these words increase in frequency at a rate comparable to the increase in shark-sightings reported for Fish Hoek beach in the month of December. But what do they really mean? Moreover, what do their really mean to the average Capetonian and can their effects be explained in a manner that is tangible to those of the far south? Allow me an attempt.


Like a human body or a modern computer, the Earth is an integrated system containing many different components which are all reliant on one another for healthy functioning. Thus, changes to one component will have knock-down effects on a wide variety of other parts and may ultimately result in complete malfunctioning of the greater biogeochemical system. Human behaviour, particularly in the form of fossil fuel burning, is responsible for changing the chemistry of the Earth’s atmosphere. The sheer number of knock down effects from this simple phenomenon is so extensive that scientists cannot hope to quantify them accurately. Some of the more well-established effects include the increase in temperature of Earth’s atmosphere, a corresponding increase in the sea-surface temperature and increased carbon dioxide uptake by the sea, which leads in increased ocean acidity. Again, what do these three broad effects mean to the average Capetonian chilling by his or her braai at the bottom of the Dark Continent? Increased global temperatures will impact on everyone’s circulation patterns. Is it possible that the frequency of the Cape Doctor’s routine summertime visits are increasing and increasing in their intensity? What is becoming of the winter time storms and how will climate changes impact on the rainfall to the Cape Town, a situation which is already dire.


The second effect mentioned; increases in sea-water temperature, is closely linked to melting of the polar ice-caps. Media has sensationally portrayed this phenomenon in those iconic and tear-jerking images of starving polar-bears stranded on fragmenting icebergs. Granted that our polar bear population has never exceeded zero, one may feel that this impact is far removed from our sub-tropical locality. Unfortunately, this is not so. Increased sea-surface temperatures also results in the thermal expansion of ocean water, effectively leading to a mean global rise in the sea-level. In the long term, residents of the valley may thus have reason to be concerned and in the short term we may all start to worry about the future of our most valuable asset; our beautiful, though not blue-flag, beach.


Finally ocean acidification, which has already seen a drop by one logarithmic pH unit, is expected to impact detrimentally on calcareous organisms. These include the magnificent and sensitive coral reefs but also organisms such as mussels and lobsters which have shells made of calcium carbonate that readily dissolve under acidic conditions. Furthermore, planktonic fish larvae are also more sensitive to such changes in ocean chemistry so our fish stocks may well further deplete beyond the already dismal levels caused by over-fishing. These species form the base of many complex food changes, so disruptions at the bottom have the potential to cause larger scale eco-system collapses.


These few examples, adapted to our locality, convey the threats associated with the global climate change phenomenon. They are just a drop in the proverbial (and heating) ocean compared to the number of other examples that I have not mentioned. Climate change is real and happening and we have a responsibility to do something about it. The non-believer may be swayed by some if the stats; the atmospheric pre-industrial carbon dioxide (a green-house gas) concentration was 280ppm and this has since risen to the current concentration of 387ppm. Should drastic action not be taken, carbon dioxide concentrations are expected to hit between 467-555ppm by the year 2050. The cynic can argue that carbon dioxide levels have been this high in the geological past, so I must stress that it is not merely the levels that should concern us, but the unprecedented rate at which we attained these levels. Past high CO2 atmospheres are characterized by more gradual nature-mediated changes which allow for organisms to adapt through evolutionary processes. The current rate at which CO2 concentration is increasing does not allow for such adaptation to occur.   


Adaptation. Nice word. And one that is destined to be used by 3rd world politicians at the upcoming COP17 summit. The last two climate summits have been debacles, to say the least, and the upcoming event in Durban may well go the same way if it is not mediated sensitively and correctly. A contentious issue exists in that 1st world countries are likely to be interested in putting together a costly mediation program involving global participation. Third world players, South Africa included, have many more pressing issues that need to be addressed prior to our involvement in a global climate-mitigation program. Many of these issues are set to be compounded by the changes in the global climate system and thus the third world country needs to focus its efforts on providing the means and skills for its citizens to adapt to a changing environment. Third world reluctance to buy into the global approach certainly makes sense from a ‘polluter pays’ perspective as most of the CO2 in the atmosphere results from the historical industrialization of 1st world countries such as Europe and the USA and the more recent rapid advancement of highly populated countries like China and India. However, this does not mean that we are absolved of all responsibility; South Africa owes it to the global community to move away from our reliance on coal as our primary source of energy. Failing that, we must focus on cleaner ways to derive our coal-fired energy, and to reduce power losses associated with the long distance transport over our extensive power-line network.


Whilst politicians handle the COP17 side of things, the man on the ground at that thin finger of land that is the Cape of Good Hope, can also do his bit to help out. Be aware of your energy use and your carbon footprint, promote a sustainable lifestyle, buy South African to cut-down on transport emissions, and educate those around you so that they too can do all of the above. And if you really want to do your bit to reduce atmospheric CO2, go swimming at Fish Hoek beach, get eaten and thereby sequester carbon to the deep ocean. Ok, that was a terrible last-ditch attempt at jest in what is not really a laughing matter. The fact that there is no lighter side to climate change has already been well established by scientists. Increasing temperatures result in increased evaporation, thus greater cloud cover and less light to the surface of the Earth. Seriously, it’s called albedo.

 Bjorn von der Heyden

Bjorn is currently pursuing a PhD in marine biogeochemistry in the Southern Ocean. He focusses on the role that iron mineralogy plays in sustaining phytoplankton growth and primary productivity. He is enrolled at Stellenbosch University and collaborates actively with researchers at Princeton University where he was based in 2010. His work involves annual visits to a synchrotron facility in Berkeley, USA, where he is able to analyze particles down to the nano size domain.

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