Aquatic biodiversity is important to the health and well-being of our planet, but is being threatened at an increasing rate. It is affected by many variables, including irrigation, contamination, and evaporation.
Irrigation is, possibly, the most subtle threat to aquatic biodiversity. Until recently, most irrigation issues were considered strictly from an engineering standpoint, with little regard to how construction and maintenance of irrigation channels would affect aquatic biodiversity. The channels were just earthworks, with no seepage protection. Over time, seepage affects a body of water’s biodiversity by changing its composition, affecting all life in or sustained by it.
Contamination of the body of water
In the past, lakes were often used as dumping grounds for waste materials. These materials are ingested by native animal and plant life, directly affecting aquatic biodiversity by killing off entire species. According to Philip Micklin and Nikolay V. Aladin’s article in the Scientific American, over the last thirty years animal life has decreased as follows: Fish species, from 32 to 6; bird species, from 319 to 160; and mammal species, from 70 to 32.
If rate of evaporation exceeds rate of rainfall, snowmelt, or groundwater supply, aquatic biodiversity is threatened.
When a body of water’s volume decreases (transforming the area into first a marsh, then dry ground, then eventually a desert) aquatic biodiversity changes as well. Micklin and Aladin state that the Aral Sea has actually suffered sufficient evaporation that it split into two smaller bodies, the Small and Large Aral Seas. The Large Aral Sea split again, into a deep western basin, a shallow eastern basin, and an isolated gulf. None are as deep as the original body of water and damage has been done to both plant and animal sectors. They further note that the marshland has decreased from 100,000 hectares in 1960 to 15,000 hectares in the 1990s.
Second, the percentage of salinity (the ratio of salt to water) can rise. Two of the smaller bodies are no longer habitable largely due to this aspect. According to Micklin and Aladin, the salinity of the Large Aral Sea has risen from about 14 grams per liter (g/l) to over 100. A typical ocean’s salinity is about 53 g/l, so this is devastating. What were once lush expanses of plant life sustained by the lake’s water are now barren except for the few varieties able to thrive in either saline soil, dry conditions or both.
If damage was restricted to this one body of water, the threat to aquatic biodiversity would not necessarily be world-threatening. The problem (exceedingly costly to fix once the damage has begun), however, is spreading. The latest victims are Central Africa’s Lake Chad and California’s Salton Sea. Unfortunately, even economically fortunate countries are cautious in allocating funds for remedying the problems. Unless ways can be found to help smaller countries, where immediate survival is often more urgent than long-term effects, we can expect these changes to continue, with disastrous effects.