On 30 April 1975 the war in Vietnam came to an end, leaving behind a landscape of plainly visible environmental devastation. Vast stretches of coastal mangroves, once home to abundant fish and bird populations, had been destroyed. Forests that had supported hundreds of plant species had been reduced to parched fragments, overrun by invasive grasses.
The term "ecocide" was coined in the late 1960s to describe the herbicides used by the US military, such as Agent Orange, and the incendiary agents, such as napalm (a highly flammable incendiary weapon based on petroleum products thickened with various substances), deployed to fight guerrillas who used the jungles and marshes as cover.
Fifty years later, Vietnam's degraded ecosystems and its dioxin-contaminated soil and water still bear witness to the war's long-term ecological consequences. Efforts to restore the damaged landscapes and to assess the long-term harm have been limited.
As an environmental scientist and anthropologist who has worked in Vietnam since the 1990s, I find the neglect and the slow pace of restoration troubling. Although the war prompted new international treaties intended to protect the environment in wartime, those efforts failed to deliver post-war restoration in Vietnam. The current wars in Ukraine and the Middle East show that these laws and treaties remain ineffective.
Agent Orange and "daisy cutters"
The US first sent troops to Vietnam in March 1965 to support South Vietnam against communist forces and the North Vietnamese army, though the war had already been going on for several years by then. To fight an elusive enemy that operated covertly at night from hideouts deep in the marshes and jungles, US forces began to use environmental modification technologies.
The best known of these was Operation Ranch Hand, during which at least 19 million gallons (75 million litres) of herbicides were sprayed over roughly 6.4 million acres (2.6 million hectares) of South Vietnam. The chemicals fell on forests but also on rivers, rice fields and villages, putting civilians and soldiers at risk. More than half of the sprayed agents consisted of Agent Orange, a defoliant contaminated with dioxins.
The herbicides were used to strip the foliage from tree canopies, improve visibility along transport routes and destroy crops thought to be supplying the guerrillas.
When news of the destruction caused by these tactics reached the United States, scientists voiced concerns to President Lyndon Johnson about the campaign's environmental impact, calling for an assessment of whether the US was deliberately using chemical weapons. The American military's position was that herbicides did not count as chemical weapons under the Geneva Protocol, which the US had not yet ratified.
Scientific organisations also launched studies in Vietnam during the war, which found extensive mangrove destruction, economic losses to rubber and timber plantations, and damage to lakes and waterways.
Evidence obtained in 1969 indicated that 2,4,5-T, a chemical contained in Agent Orange, caused birth defects, because it contained TCDD, a particularly harmful dioxin. As a result, in April 1970 the substance was banned for domestic use, and in April 1970 the military discontinued its use of Agent Orange, with the final mission flown in early 1971.
Incendiary weapons and deforestation devastated Vietnam's rich ecosystems
The US Forest Service tested jungle burning on a large scale, igniting drums of diesel fuel dropped from aircraft. Napalm bombs, which consumed more than 400,000 tonnes of thickened petroleum over the course of the war, were especially feared by civilians. In the hardened, barren soils left behind by this destruction, invasive grasses often took root.
"Rome ploughs" – massive bulldozers fitted with an armoured cutting blade – could clear 1,000 hectares a day. Enormous blast bombs, known as "daisy cutters", literally levelled forests to the ground and generated shock waves that destroyed everything within a radius of 3,000 feet (900 metres), right down to the earthworms living in the soil…
The US also engaged in weather modification, carrying out Project Popeye – a classified programme – between 1967 and 1972. Under the programme, clouds were seeded with silver iodide to extend the monsoon season, in an attempt to disrupt insurgent activity and the flow of supplies from North Vietnam along the Ho Chi Minh Trail. Finally, in 1973 Congress passed a bipartisan resolution calling for an international treaty that would ban the use of weather modification as a weapon of war. The treaty came into force in 1978.
The US military argued that these tactics were also successful in operational terms, since the forests were removed as a "guarantee of American safety".
Despite objections from Congress, the environmental impact of US military operations and technologies was subject to little scrutiny. Research sites were difficult to reach, and no routine environmental monitoring was carried out.
Restoration efforts have been slow
After Saigon fell to North Vietnamese forces on 30 April 1975, the US imposed a trade and economic embargo on the whole of Vietnam, leaving the country both war-damaged and without funds.
Vietnamese scientists reported small-scale studies. One found that the forests had suffered a sharp decline in bird and mammal diversity. In the A Lưới valley in central Vietnam, 80% of the forests treated with herbicides had still not recovered by the early 1980s. In these areas, biologists recorded only 24 bird species and five mammal species — far fewer than would normally be found in forests that had not been treated with herbicides.
Only a handful of ecosystem restoration projects were attempted, hampered by small budgets. The most notable began in 1978, when foresters started planting mangroves by hand at the mouth of the Saigon River in the Cần Giờ forest, at the time a completely stripped area.
Inland, large-scale tree-planting programmes finally began in the late 1980s and the 1990s, but they mainly planted trees exotic to Vietnam, such as acacias, which did not restore the original diversity of the natural forest.
Chemical clean-up is still under way
For years the US denied any responsibility for cleaning up the chemicals in Agent Orange, despite the identification of dioxin-related illnesses among US veterans and tests revealing that exposure to dioxins may still be affecting tens of thousands of Vietnamese people.
The two countries did not reach their first agreement on clearing up the contamination until 2006, when veterans, scientists and non-governmental organisations campaigned persistently and succeeded in getting Congress to allocate 3 million US dollars to clean up the contamination at Da Nang airport.
The project, completed in 2018, treated 150,000 cubic metres of dioxin-contaminated soil, at a cost of more than 115 million US dollars, paid for mainly by the US Agency for International Development, or USAID. The clean-up required draining lakes and treating contaminated soil that was poisoned 3 metres deeper than had been predicted. The soil had to be piled up and heated so that the dioxin molecules would break down.
Another significant "hotspot" is the heavily contaminated area around Biên Hoà air base, where local residents continue to ingest large quantities of dioxin by eating fish, chicken and duck.
Drums of Agent Orange were stored at the base, and large amounts of the toxin leaked from them into the soil and water, where it continues to accumulate in animal tissue as it moves up the food chain. Remediation work began in 2019, but US President Trump's administration is set to shut down USAID in the near future, so it is unclear whether there will be American experts in Vietnam to oversee this complex project.
Legislation to prevent further "ecocide" is complicated
While the health effects of Agent Orange have clearly attracted attention, its long-term ecological consequences remain poorly studied.
Scientists today have far more tools at their disposal than they did 50 years ago, including satellite imagery, which is being used in Ukraine, for example, to identify fires, flooding and pollution. Yet none of this can replace observation on the ground, which is often restricted and, in wartime, extremely dangerous.
The legal position is problematic
The Geneva Convention, which governs conduct in wartime, was revised in 1977 to prohibit "widespread, long-term and severe damage to the natural environment". A 1980 protocol restricted incendiary weapons. Yet the oil fires started by Iraq during the 1991 Gulf War and the recent environmental damage in the Gaza Strip, Ukraine and Syria show that treaties cannot be relied upon without robust enforcement mechanisms.
An international campaign is currently under way calling for the Rome Statute of the International Criminal Court to be amended to add ecocide as a fifth punishable crime alongside genocide, crimes against humanity, war crimes and aggression.
Some countries have passed their own ecocide laws. Vietnam was the first to establish in its criminal code that "ecocide, destroying the natural environment, whether committed in time of peace or war, constitutes a crime against humanity". Yet despite a number of serious charges in pollution cases, this law has not led to a single prosecution.
Both Russia and Ukraine also have ecocide laws, but these have not prevented damage or held anyone to account for the harm done during the ongoing conflict.
A lesson for the future
The Vietnam War is a reminder that failing to address ecological problems, both during a war and after it, will have long-term consequences. There is still a lack of political will to ensure that devastating harm to nature is neither ignored nor repeated.