Case Study: the Aral Sea

Today's post on the Aral Sea slightly deviates from the topic of food, but because it is one of the most catastrophic examples of the environmental impacts of intensive agriculture, I thought it deserved a place on this blog. So let's begin...

Abandoned boats scattered across desiccated areas
of the Aral Sea (Photo by Audun Kjørstad)

The Aral Sea, a large saltwater lake shared between Kazakhstan to the north and Uzbekistan to the south, was once the world's fourth largest body of inland water behind the Caspian Sea, Lake Superior, and Lake Victoria (Micklin, 1988). The Aral Sea drainage basin covers 1.8 million km² within seven nations, and is a terminal lake, i.e. it has surface inflow but no outflow (Micklin, 2006). It has experienced dramatic desiccation during the 20th century as a result of the diversion of riverine waters for agricultural irrigation from the Syr Dar'ya and the Amu Dar'ya starting in the 1960's. The Syr Dar'ya and the Amu Dar'ya are the main sources of water to the Aral Sea, and by the 1980's, these two rivers virtually dried up (Encyclopaedia Britannica, 2014).

The Aral Sea basin (Micklin, 2006)

Until 1960, the Aral Sea was a brackish lake (mean salinity of 10 g/L) that was inhabited by freshwater species. It supported a major fishery and was also used as a regional transportation route. In addition, the deltas of the Amu Dar'ya and the Syr Dar'ya supported rich bioligical diversity as well as activities such as irrigated agriculture and animal husbandry, among others (Micklin, 2006). It is interesting to note that the Aral Sea has been repeatedly flooded and desiccated throughout the Pliocene, the most recent replenishment occurring during the Pleistocene around 140,000 years ago. Over the past 10,000 years, fluctuations in the Aral Sea's surface level ranged from 20 to 40m as suggested by evidence such as marine fossils, archaeological sites and the like (Micklin, 1988).

Average annual water balance for the Aral Sea between
1911 and 2005 (Micklin, 2006)

What happened in 1960 that prompted the Aral Sea's tipping point? In the early days of the Soviet Union, communist authorities devised plans to increase the production of cotton, or white gold. Cotton production was increased in the 1920's, and by 1950 hundreds of kilometers of unlined canals from the Amu Dar'ya and Syr Dar'ya were carved into the surrounding desert to irrigate new cotton plantations (Stone, 1999). The effects of the rerouting of the two rivers were immediately felt, with major water deficits occurring by the 1980's, as can be seen from the above figure. Since 1960, the profile of the Aral Sea has been drastically modified due to this irrigation. Between 1987 and 1989, it was split into a "Small Aral Sea" in the north and a "Large Aral Sea" in the south. By 2005, the Large Aral Sea had become separated into three distinct bodies (Micklin, 2006).

Changes in the profile of the Aral Sea (Micklin, 2006)

So, why is all this important? The desiccation of the Aral Sea led to environmental impacts such as the loss of wetlands as a result of reduced river flow and the loss of fish species due to breeding ground destruction and increased salinity (Micklin, 2008). In terms of human impacts, the disappearance of the inland sea prompted the collapse of local fisheries, the end of shipping routes, and the exposure of a seabed rich in salt, pesticides, and other agricultural contaminants which can be transported by toxic dust storms (Micklin, 2008; Stone, 1999). Vozrozhdeniya (Resurrection) Island in the centre of the Aral Sea was once used as a ground for biological weapons testing. In 2001, the island was joined to mainland, creating a risk of human exposure to these weaponised organisms (Micklin, 2008). 

Resurrection Island (Micklin, 2008)

What's been done to alleviate the situation? In the 1990's, Kazakhstan attempted to restore the Large Aral Sea by constructing a dike to block outflow to the south, which was destroyed by a catastrophic failure in 1999. In 2005, however, a 13km earthen dike with a gated concrete dam for water discharge was installed with the aid of funding from the World Bank. This has led to an 18 percent increase in area of the northern portion of the Aral Sea, and fish are now being caught again in the area (Micklin, 2008). The Aral Sea has shown signs of restoration since then (e.g. Pala, 2011), and time will tell if the southern portion of the sea will one day reappear.

To conclude this post, I'm leaving you with this video of Bruce Pengra explaining how Landsat imagery has been used to document the Aral Sea's decline through time. It's truly amazing to see how the lake has transformed throughout the years. The disappearance of the Aral Sea is undoubtedly one of the great examples of global environmental change through time, and has taught humanity lessons on the effects of over-exploitation of natural resources from delicate ecosystems.

Thanks for reading!