A Vanishing Sea of Toxic Dust Storms

In the last Climate Change MSc lecture of 2015, a case study was presented regarding the changes that have happened in a relatively short space of time in the Aral Sea, on the border between Kazakhstan and Uzbekistan. Figure 1 below clearly shows the reduction in the area covered by water in the sequence which runs from 2000 to 2015.

Figure 1: Aral Sea satellite image sequence from 2000 to 2015 (looping). The black outline is the approximate lake shoreline in 1960. Source: Constructed animating gif from NASA Earth Observatory images.

Otherwise known as the ‘Sea of Islands’, this endorheic sea was once the fourth largest inland sea in the world, and allowed fishing communities and agriculture to sustain themselves for decades in the early half of the 20^th century. As an endorheic sea (meaning no outflow to the ocean) it acts as a terminus for surrounding hydrological systems, also termed as a terminal lake. Terminal seas and lakes such as this are very sensitive to changes in climate, for example through changes in evaporation rates. In fact, the Aral Sea has undergone a cycle of drying out and filling up over the past 10 thousand years (Micklin 2007).

Another picture, Figure 2 (sourced cited by an article on the Aral Sea Crisis by Columbia University) shows some older images than Figure 1, which highlight the longer term reduction.

Figure 2: Clear reduction in Aral Sea. When combined with Figure 1 we see the extremes of the reduction in water surface area. Source: http:/www.envis.maharashtra.gov.in and cited by Thompson 2008

The main cause for this reduction was the development of the Karakum Canal, built for agricultural irrigation, shipping and fisheries allow for economic development of Turkmenistan. It was started in 1954 and completed in 1988. It has enabled huge areas of Turkmenistan to be committed to high intensity agriculture, essentially draining the Aral Sea of water.

The reason for this huge engineering endeavour was the farming of cotton. The cotton, nicknamed ‘white gold’, requires a huge amount of water. To make matters worse the engineering practices used to construct the canal allow around 50% of the water to be lost into the ground and to evaporation.

Impact

Micklin noted the reduction in water surface area to be around 75%, and the lake level reduction to be around 23 to 30 meters (Glantz 2007), which led to a volume reduction of 90% and an increase in salinity of over an order of magnitude, from 10 g/l to over 100 g/l. This lead to tragic and severe impacts to the local ecosystems, mainly fish species, as well as enhancing the frequency of dust storms to roughly ten per year (Glantz 1999, cited by an article by Thompson in 2008 on the Columbia University website). These impacts deveastated local communities and made the area extremely inhospitable. 

Knock on impacts on local communities and industries are numerous. Obviously, the fishing industry in the sea has been decimated due to increasing salinity and agricultural practices are now hampered by the loss of water resources. Mammals and birds have also seen sharp decline in species diversity: from 1960 to 2007, the area lost roughly half of the number of species (Micklin 2007).

The other major impact of over 36,000 km² (Wiggs et al. 2003) of dusty seabed being created is that there is now a large source of extra dust available to be picked up by the winds and on occasion whipped into dust storms (Figure 3). Roughly ten dust storms occur in the region per year (Glantz 1999, cited by an article by Thompson in 2008 on the Columbia University website).

Figure 3: Dust storms on the coast of the Aral Sea in May 2007 (Source: NASA)

Agricultural waste products containing pesticides, insecticides, herbicides and fertilisers have drained into the sea, accumulated over time, and then once the sea dried, they became baked into the exposed sediments. The desiccated land surface also potentially contains remnants from Soviet Union's biological warfare testing in the 1950’s, including Antrax, which is just waiting to be transported around by the aeolian processes. Vozrozhdeniye island, also known as Resurrection island, remained a controversial subject as it was one of the chief locations for such testing.

Wiggs et al. (2003) studied the link between aoelian dust and child health in the populations close to the Aral Sea, and found some associations to local respiratory illness in local populations, although there are significant long-distance sources of dust in the region too. Micklin (2007) also confirmed this negative impact on human health and agriculture in the wider area from dust storms that can grow to be 500km in size.

Climate perspective

Although the case of the Aral Sea’s reduction is an extreme example, it seems fair to assume that endorheic lakes will see pressure due to global climate change (Timms 2005), whether there is significant human influence or not. The Aral Sea has suffered from a two-pronged attack as the region undergoes warming, and agricultural exploitation and over-use. Strategies to preserve the remaining water in the North Aral Sea through damming projects after the sea split in to two basins in 1987, seem to be successful, which will enable the communities in the area to hold on to their way of life to an extent.

The former majesty of the larger portion of Aral Sea (the Big Aral), now seems to resemble no more than a salty (and toxic) dust bowl, with former islands now parched monuments to the impact of cotton farming and climate change, although to a lesser but still significant extent, (Aus Der Beek et al. 2011). The region will only come under more pressure if water resources become scarcer in the area linked to global warming and high evapotranspiration rates. 

Small et al. (2001) examined how the desiccation of such a large area through excessive irrigation has modified the sea surface temperatures, precipitation regimes and the hydrological cycle in the area. I wonder if the original plans to build the Karakum Canal took any of these knock-on effects in to consideration.

To end, I’ll post this interactive storymap hosted by Esri which highlights some human induced change since 1990 using the Landsat satellite imagery from NASA. The first example is the Aral Sea and, you can see again, by swiping the dividing line, how the lake has undergone a dramatic and rapid drying out in the last 25 years. The other pages of the map, also show cases of anthropogenic land use change from urban expansion, damming, land reclamation, and agricultural uses.

*UPDATE*
My brother's comment below makes a very good point regarding the fact that such a sad story, now serves as a an evocative reminder of the impact of human over exploitation of the environment. This reminder should be documented as it happens, not only in scientific literature, but in art too. We are both keen photographers, and so I thought I'd add this link to herwigphoto.com's Aral Sea project. Some amazing and poignant images.