Vulnerability of Southern African Coastline

Current climate change has been attributed to the emissions resulting from anthropogenic activities. Although developed countries emmit the largest percentage of greenhouse gases that warm the earth, they are not the countries who will be most affected or harmed the implcations of climate change. Instead, the developing countries absorb most of the hardships born by climate change. All countries will have to bear the burden of something like temperature increases but it will greatly affect developing coastal countries who are also concerned with their vulnerability to consequential sea-level rise and ocean acidification.
 
 

Temperature Increases

Temperature increases have been attributed to anthropogenic emissions of greenhouse gases decreasing heat's ability to leave Earth's atmoshpere and return to space. during the last 150 years following the industrial revolution, the global average temperature has warmed by ~0.6ºC (Hardy, 40). Although this may not seem like a great deal it greatly changes the Earth's water cycle and how much glacial and ice quantities are storing water. As a result of increasing temperatures, ice cap and glacier melt increases and the oceans expand due to both the quanitiy additions made from the melting ice as well as from water expansion.  It has been predicted that these affects will combine to increase sea level by ~5.9 inches by 2050 and by ~13.8 by 2100 (Pinet, 540). 
 

        Ecosystem Reactions

Atmosphereic temperature increases likewise increase the temperatures of the oceans due to atmospheric & oceanic interaction. Oceanic temperature increases pose a problem for all marine organisms because they drastically change the ecosystems that have adapted to a certain way of life. Increasing temperatures will change the balance of ecosystems in that it will make some species become invasive species and move to new areas that are similar to their old ones. Others simply may not be able to adapt and consequently become extinct, while others quickly evolve to reduce their vulnerability. Changes like these can be quite detrimental to species because new predators are emerging as well as a possible abundance of pests because their predators moved to a more temperate climate. In terms of coastal regions with coral reefs, temperature increases can have detrimental affects.
 
 
Coral reefs are especially vulnerable to temperature increases in that if they are exposed to ocean temperatures that are 1.8ºF above their monthly average then they bleach (NOAA).  Bleaching is the process where coral reefs loose their color because their dinoflagellate symbionts (the small organisms that live in the coral) leave because they cannot handle the stress of the increased temperatures. When this happens the coral most often dies if the dinoflagellates do not return to them. If they do return to the coral, the ecosystem still has problems recovering. Because the temperature increases have weakened the coral, the organism is more seceptible to disease and do not grow as quickly (Hoegh-Guldberg, 1740).
 
 

        Implications for Southern African Countries

Several African countries recieve the benefit coral reef ecosystems (mangrove ecosystems) serving as natural barriers. These barriers not only provide steady streams of economic revenue to developing African countries but prevent the erosion of the coastlines. When coral bleaching occurs in response to temperature change, the coastlines become more vulnerable as the abrasive forces from waves and storms degrade the weakened corals. When the corals can no longer withstand the stress of marine temperature increases the coral dies and with it the effective barrier against coastline erosion. As a result the ocean consumes the coastline and the valuable resources that coastline communities extract from it (fishing success etc.)

Ocean Acidification

Ocean acidification is the profess in which the ocean absorbs CO2 and other greenhouse gases through oceanic and atmospheric interaction. When carbon is absorbed by the ocean it reacts with the water’s salty composition to produce carbonic acid thus making sea water more acidic and decreases its pH. Over the course of 1 year the ocean absorbs about 1.3 Pg Cy-1 of carbon from the atmosphere (Mann 393).
 

Ecosystem Reactions

Ocean acidification poses a great problem for any marine wildlife that rely on calcareous shell or structure. In the ocean becoming more acidic it will be increasingly difficult for organisms for make their calcium shells because the ocean water will be constantly attempting to dissolve them. This poses a threat to plankton that use calcium to make their shells. Ordinarily one species would not have an enormous effect on an ecosystem as vast as the world's oceans

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but this case is the exception. In plankton and othe calcareous diatoms being at the very bottom of the food chain, nearly every species relies on their multiplication in order to feed other species continuing up on the food chain. When plankton are negatively affected by ocean acidification so will all other species that depend on animals that feed on them.
 
Ocean acidification also threatens to dissolve coral reefs because their structure is mostly made of calcium carbonate. More specifically the coral will react to ocean acidification by: decreasing their linear extension rate, reduce their skeletal density or they will maintain their skeletal growth and density but at the expense of chronic stress and greatly reduced reproduction. None of which are positive outcomes to oceanic carbon absorption.
 
 

 Implications for Southern African Countries

In the oceans acidifying and degrading corals ability to multiply, coral reefs will shrink and consequentially allow the oceans to more easily erode Southern African coastlines. As for the dissolving of the shells of calcareous plankton and diatoms, this will affect the amount of fish and other important animals used commercially as a source of food and as an important component of export revenue and GDP.   
 
 

Sea-Level Rise

Sea-level rise is attributed to a combination of the impacts of humans and natural chemical properties. It has been established that humans emit greenhouse gases which warm the earth and consequentially melt glaciers, but the increase of oceanic temperatures also contribute to sea-level rise because of water expansion as temperature increases.
 

Ecosystem Reactions

As sea-level increases ecosystems would be constantly changing in efforts to adapt to these new developments.

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Some species would easily adjsut but others are not so mobile. The coral reefs for example are greatly affected by sea-level rise. Not only will they be unable to keep up with sea-level rise after a certain point but as they die they will no longer provide the effective coastal barrier they once did. As a result the ocean will more easily consume larger proportions of Southern African coastlines.

Implications for Southern African Countries

All countries will beaffected by sea-level rise but especially Southern African countries because of their already vulnerable state. Currently more than 1/4 of Africa's population lives within 100km of a coastal area (Desanker, 515). The anticipated sea-level rise will most likely displace this significant amount of people, forcing them to move, which is not only an inconvenience but a financial nightmare to relocate entire cities that do not have a substantial amount of money or constant revenue to speak of.Current models show that if the sea-level were to rise by 38cm by 2080 the number of people in Africa impacted by flooding and other problems could reach up to 70 million people in a worst case scenario (IPCC 2001). It has also been anticipated that a rise in sea-level will result in the “intrusion of salt water into estuaries, rivers, and streams, and seepage willcontaminate coastal aquifers, raising the water table and rendering some groundwater supplies undrinkable" (Pinet 540).The seepage of salt water into these sources will also salinify the ground and agricultural resources will become unproductive because the fertility of the soil will have vanished due to addition of salt, which will increase the vulnerability of Africa's coastal countries even more. Not only will the anticipated sea-level rise infiltrate water ways but it will also consume other resources that developing Southern African countries use as large sources of revenue. For example, there is a great number of diamond, gold, silver and other mines that could be consumed by the waves of the ocean which would increase Southern African vulnerability even more because those sources of revenue would no longer be easily exploited.
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