The first casualty of warfare is truth – usually swiftly followed by humans – but often overlooked is the damage done to the ecosystem. 

From the Belgian and French fields left trench-scarred by World War I to the Japanese cityscapes forever changed by World War II's explosive nuclear conclusion, battlefields cause loss of life way beyond the human victims.  

The current conflict in Ukraine is leaving its own legacy on the region's ecology – and perhaps the biggest single event is the flood caused by the destruction of the Kakhovka dam. Kyiv and Moscow have blamed each other for the dam-breaking explosions, in the Russian-controlled Kherson region; but whatever the cause, the effect is the same – potential devastation of the ecological environment over a huge area. 

The soundbites paint the picture, with politicians and scientists alike warning of "an environmental bomb of mass destruction" causing "colossal environmental damage" that will "destroy the biodiversity" – an "ecological catastrophe" of fields "turning into deserts" in "the worst environmental disaster in Europe since Chernobyl."

One expert said the flooding "will definitely have extensive long-term ecological and environmental negative consequences not only for Ukraine but for neighboring countries and regions," while another word rang across the world: "ecocide."

But what are the effects, and the risks?

Poisoning the water

Floods cause huge destruction in various ways. First there is the sheer power of the onrushing water, then there is the detritus swept along by it. This flotsam includes dangerous materials usually kept well away from humans. Flooding can lethally distribute poisonous substances even in the 'cleanest' areas, let alone an industrial heartland transformed into a war zone.  

This was no minor dam. Built in the Soviet era, it's one of six that hold back the Dnipro river, which stretches from the very north of Ukraine to the Black Sea. At 2,200 kilometers long, the Dnipro (known to Russians as the Dnieper) is Europe's fourth-longest river, draining half a million square kilometers. 

The body of water behind the dam was one of the continent's largest reservoirs. Covering more than 2,000 sq km, 240 km long and up to 23 km wide, it was locally nicknamed the 'Kakhovka Sea.' Now that sea is flooding the land downstream – where, broadly speaking, Russian forces occupy the south-eastern left bank and Ukrainians the north-western right bank. 

Ukraine's President Volodymyr Zelenskyy immediately warned that the river had been contaminated with 150 tons of industrial lubricant, with another 300 tons at risk of leaking. 

"An oil slick of at least 150 tons formed and was taken by the current to the Black Sea," said Zelenskyy, who called the event "ecocide": "We cannot yet predict how much of the chemicals, fertilizers and oil products stored in the flooded areas will end up in the rivers and sea."

Environmental experts were horrified. "Just 1 liter of oil can contaminate 1 million liters of water. So 150 tonnes will have numerous impacts on Ukrainian water resources and the environment," said Yevheniia Zasiadko, Head of Climate Department at Kyiv-based environmental non-profit Ecoaction. 

"Oil spreads over the surface in a thin layer that stops oxygen from getting to the plants and animals that live in the water," she said, noting that the Dnipro draining into the Black Sea threatened to "affect the marine ecosystem" there and warning that riverside gas stations and sewage treatment plants downstream presented additional pollution risks. 

In subsequent days, the estimated volume of pollution has risen. As the reservoir was designed to fuel a hydroelectric power plant, a generation station stood in the way of the floodwaters. 

"Four-hundred tons of turbine oil is always there, in the units and in the block transformers that are usually installed on this equipment," said Ihor Syrota, the CEO of power company Ukrhydroenergo. "It all depends on the level of destruction of the units and this equipment… If the damage is extensive, then all the oil will leak out."

Sure enough, the numbers rose again. "Now we know that potentially 600 or maybe even 800 tons of oil have been released into the water," Ukrainian Environment Minister Ruslan Strilets said. "This oil spill will drift into the Dnipro, and I'm sure that it will be in Black Sea."

Nor is it just oil that's floating downstream. This is, after all, a war zone. The floodwaters have dislodged landmines which are now drifting downstream, threatening residents and rescuers alike. 

"This is both a water element and a mine hazard, because mines float here and this area is constantly under fire," said Oleksandr Prokudin, the head of Kherson's regional military administration, who has been overseeing rescue efforts.

The deadly risks of floating mines were summarized by Erik Tollefsen, head of the Red Cross's weapon contamination unit: "All we know is that they are somewhere downstream."

After the floods, the desertification

After the flooding comes the opposite problem: desertification. One is sudden but temporary; the other is slower but can be much harder to reverse.

Olexi Pasyuk, a campaigner with environmental group CEE Bankwatch, said the flood's "temporary impacts" might only last a week. "However, later on the bigger impact will be caused by lack of water as Kakhovka reservoir is a source of water for the watering system of south Kherson region," he added. "We can expect significant problems for agriculture and for local people who live off it."

Flooding washes away crops and soil, making it harder for farmers to successfully grow the vital produce that gave Ukraine the "Europe's breadbasket" nickname. Add in that 2,000 sq km of fertile farmland was irrigated by water from Kakhovka reservoir, and the risk is that poisoned farmland denuded of topsoil could also face drought.

That would cause risks in the short and long terms. Farms without irrigation in the summer months would affect food production and security; fields left empty in drought conditions create ideal 'dustbowl' circumstances for further degradation.

Speaking to the UN Security Council on Tuesday, UN aid chief Martin Griffiths called the dam's collapse the conflict's "most significant incident of damage to civilian infrastructure," with "grave and far-reaching consequences for thousands of people in southern Ukraine – on both sides of the front line."

"The dam is a key source of agricultural irrigation in southern Kherson and the Crimean peninsula," he said, warning that flooding will "disrupt farming activities, damage livestock and fisheries, and bring widespread longer-term consequences. This is a massive blow to a food production sector which is already significantly damaged."

The dam collapse has left 94 percent of irrigation systems in Kherson, 74 percent in Zaporizhzhia and 30 percent in Dnipro regions "without a source of water," according to the Ukrainian Agricultural Ministry, which warned of "fields in southern Ukraine perhaps turning into deserts."

It will also affect Russian-controlled land on the Crimean peninsula, which relies on water from mainland Ukraine – Russian troops last year reopened a water channel linked to the Kakhovka reservoir which Ukraine had closed after Crimea came under Russian control in 2014.

"It's going to be a social-economic disaster. Farmers won't be able to grow crops," said Wim Zwijnenburg of Dutch non-governmental organization PAX. "Ukraine had already [blocked] the river to Crimea prior to the conflict to stop the water flow, which already led to some desertification in the area. It's hard to predict anything — most of the effects will probably play out in two to three years' time."

Wildlife at risk

It's not just crops at risk: The dam disaster will have wide-ranging effects on wildlife. No wonder Ukraine's Deputy Foreign Minister Andrij Melnyk called it "the worst environmental disaster in Europe since Chernobyl." 

"First of all, the Kakhovka reservoir is likely to be drained to zero, and we understand that the number of fish will gradually go down," said power company boss Ihor Syrota. Ukraine's defense ministry said that floodwaters killed around 300 animals at the Nova Kakhovka zoo. And the flooding will affect delicate downstream ecosystems like the Black Sea Biosphere Reserve, home to thousands of species, and the Oleshky Sands desert.

"Due to the comprehensive damage done to the area, this is the biggest ecocide in Ukraine since the beginning of the full-scale invasion," said Deputy Minister of Environmental Protection and Natural Resources Oleksandr Krasnolutskyi. 

"Along the territory where the water is flowing, there were natural parks created with the goal of preserving threatened or unique animal and plant species found on the Red List. We are worried these species will stop existing," continued Krasnolutskyi.

Some Ukrainian regions are part of the pan-European 'Emerald Network' – areas of special conservation interest which partly function as vital wildlife corridors. 

"The Emerald Network includes territories intended for bird migration and nesting. European regulation stipulates that these areas need to be protected in order to not disrupt the migration patterns of these species," Krasnolutskyi said.

Such rich ecosystems can take decades to create but be lost in days, warned Modupe Jimoh, assistant professor of Civil and Humanitarian Engineering at the University of Warwick. 

"In places where you have biodiversity that has developed for a lot of years, it means that it would take a lot of years to reverse the damage first, and then to build it (up) again," she said. "In the washing away of the water, some species would be lost forever."

Ukrainian Environment Minister Ruslan Strilets warned of the risks to downstream wildlife species found nowhere else in the world, including the sandy blind mole-rat. No wonder Iiulia Markhel, of environmental organization Let's Do It Ukraine SOS, called the events a "catastrophe."

"Animals, species, will be destroyed," she warned. "It will change the climate of the whole region. Ukrainian agrarian lands have likely been destroyed. The area will be flooded. The places the water will leave will turn into deserts; the places the water will stay and will become swamps."

The reaction

Words are easily spoken and headlines quickly generated, especially in a time of claim and counterclaim – remember that line about truth being the first casualty of war? However, the soundbites about the Kakhovka dam disaster suggest genuine fear as to its effects.

The UN Secretary-General Antonio Guterres called the flooding an "ecological catastrophe," while Zelenskyy called it "an environmental bomb of mass destruction" and his environmental minister Krasnolutskyi warned "what happened will result in colossal environmental damage to our ecosystems."

Blaming Russia for the explosions at the dam, Ukraine's Prosecutor General's Office said "Ukraine has initiated proceedings over this crime, qualifying it as a violation of the laws and customs of war and ecocide. It has caused severe long-term damage to people and the environment. The consequences are catastrophic… land has become unsuitable for agriculture."

However, Russia – which also has a lot to lose from the destruction of the dam – insists it is not to blame. On Tuesday, Moscow's foreign ministry said the breach "has caused devastating damage to the farmland in the region and the ecosystem at the mouth of the Dnieper river," and noted that "the inevitable drop in the water level of the Kakhovka reservoir will affect Crimea's water supply and will hinder the improvement of agricultural land in the Kherson region."

Zhang Jun, China's permanent representative to the United Nations, said "We express our grave concern over the destruction of the dam at the Kakhovka hydroelectric power plant. We are deeply concerned about the resulting humanitarian, economic, and ecological consequences. We call on all parties to the conflict to abide by international humanitarian law and do their utmost to protect civilians and civilian infrastructure."

The situation was calmly, if worryingly, summarized by Mohammad Heidarzadeh, a senior lecturer in civil engineering at the University of Bath: "It is obvious that the failure of this dam will definitely have extensive long-term ecological and environmental negative consequences not only for Ukraine but for neighboring countries and regions."

In those Flanders fields devastated by World War I, poppies now bob their heads in the wind; Hiroshima and Nagasaki have zoological parks. Nature usually returns in some form – but only at its own pace, and often having adjusted to differences caused by humankind. The long-term effects of the Kakhovka dam disaster may only be discovered by generations yet to come.

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