Some environmental disasters happen in the blink of an eye, much too quickly for anyone to react: an oil spill, a nuclear explosion, the sudden collapse of a tailings dam.
They are often the result of an operator's error, or sloppy inspection, or adverse weather conditions no one could have foreseen.
Mistakes happen, we say, because life is like that. The world is unpredictable and, as rigorously as we try to meet its contingencies, nature's play of atoms - or the game of chance - is too complex for us to fathom. To err is human.
But there is another group of eco disasters that are years, sometimes decades in the making. It is hard to trace them back to a single source because the gradual accumulation of bad judgments, blind ideology, indifference, greed, or plain stupidity is so enormous that it defies all logic.
Such an example is the massive diversion of rivers in the Soviet Union that, over a period of 50 years, has led to the demise of Central Asia's Aral Sea. Another is the damming of the Colorado River.
Another dark legacy of the 20th century - Sasyk Lyman
Although not nearly as famous, and playing out on a much smaller scale, Sasyk Lyman - on the Black Sea coast of Ukraine south-west of Odessa near the border with Romania - stands out as another testimony to the devastating environmental policies of the 20th century.
The origins of the catastrophe date to the late 1960s and early 70s, when the Soviet Union began the planning of a huge land-reclamation project in the dry steppes of southern Ukraine with the goal to increase agricultural input.
It envisioned the construction of a complex irrigation network that would connect, through a series of inter-basin transfer canals, the three major European rivers on the northern coast of the Black Sea: the Danube, Dniester, and Dnieper.
As part of the project, it was decided that the series of brackish bays, estuaries, lakes, and lagoons along the Black Sea coast (collectively known in Russian as lymans) would be incorporated as sort of aqueous stepping-stone system.
The idea was to cut off the lymans from the sea, link them with artificial canals and pumping stations, and gradually enable their conversion into a network of freshwater reservoirs.
'Nothing went as planned' - 30,000 hectares of fertile soil destroyed
The Danube-Dnieper Complex had to divert 16 cubic kilometers of water annually and irrigate some 8.7 million hectares of land.
In its scale and pure madness, it was similar to the Soviet Union's other gargantuan project of the same period, the Northern River Reversal, which intended to divert the flow of Siberian rivers to the southern steppes of Central Asia.
The first part of the project, the Danube-Dniester Irrigation System (DDIS), commenced in 1976 at Sasyk Lyman, a 210 square kilometre lagoon near the southernmost point of Ukraine. For the purpose, Sasyk was linked to the nearby Danube Delta by a 13.5-kilometer long canal, while a 14-kilometer concrete dike cut it off its opening to the sea.
Giant pumping stations began taking out the salt water and replacing it with Danube water. It was believed that three 'washes' over a period of 18 months would completely convert the former Black Sea lagoon into a freshwater reservoir.
Nothing went as planned. Although the salinity in Sasyk decreased substantially, salt water continued to enter the basin from springs connected to underground caverns.
By the early 1980s, with tens of millions of dollars already invested in the project, irrigation went ahead anyway, despite the fact that the levels of dissolved salts were too high (1.6 grams/liter) for agriculture.
As a result, nearly 30,000 hectares of prime chernozem (black-earth) soil were irreversibly destroyed.
Tourism, fisheries collapse. Enter schistosomiasis
The engineers decided to raise the level of Sasyk by half a meter in order to further dilute the salts, but that did not help either and only contributed to the erosion of the coast. Locals started joking bitterly that non-irrigated lands produced better harvest than irrigated ones.
The tourist industry suffered substantially as well. The Sasyk lagoon had once been a prime summer vacation spot in the Soviet Union, with hotels and health spas dotting its coast, the beaches packed with visitors.
When the irrigation project began, tourism quickly disappeared and the entire industry fell apart. The populations of marine fishes collapsed and so did the once substantial fishing industry in the area. Levels of local unemployment and poverty rose and people started to leave.
After the dissolution of the Soviet Union in 1991, Ukraine's economic crisis and high electricity prices made the operation of Sasyk's main pumps untenable. But that only worsened the environmental problems, as circulation of water stopped and toxic blooms of blue-green algae intensified, depleting oxygen levels.
What followed was a mysterious spike in respiratory illnesses, rashes, hepatitis, and certain cancers among the local population, especially among children. The water became infested with schistosoma parasites, a flatworm, which causes potentially lethal complications in humans. Nobody dared to swim in Sasyk anymore.
'Return Sasyk to the sea!'
Residents have not stood by quietly. For nearly 20 years now they have been calling for the dismantling of the concrete dike and "returning Sasyk to the sea".
Irina Vykhrystiuk, a local environmental activist, headed for many years an NGO called Vidrodzhennia (Renaissance), focusing on the plight of Sasyk and advocating the removal of the dike.
"I'd like to return Sasyk to the way I knew it", she says, "so that my own children and grandchildren could see at least a bit of what we once had."
According to polls conducted among the local population, 97% of respondents are in favor of such measures. There were mass protests in 2008, when over five hundred people came out on the dike to ask for its removal.
However efforts have been thwarted by some local businesses, which own stakes in a freshwater fishery at Sasyk, and the Danube-Dniester Irrigation System - which is oddly still in existence and continues to receive state funding, despite the fact that there is no more irrigation and much of the pipe and pumping infrastructure has been dismantled.
But with other priorities holding sway in present-day Ukraine, the prospect of "returning Sasyk to the sea" is still far away, with neglect the most likely outcome for many years to come.
To walk along its coast today, meanwhile, is to catch a glimpse of a human-made apocalypse. A grey, empty expanse of water. Dilapidated villages and sanatoria overgrown by grass. Old coastal cemeteries eroded by high water, bones and coffins exposed to the air.
Sasyk is the place where even the dead feel betrayed.