Most World War I trenches were either filled in and returned to farmland, absorbed into expanding forests, or left to slowly collapse into shallow grassy ditches. But “returned to normal” understates what actually happened. The Western Front left behind a landscape so toxic, so littered with explosives, and so scarred that parts of it remain off-limits to this day, more than a century later.
The Zone Rouge: Land Too Damaged to Live On
Immediately after the armistice in 1918, the French government surveyed the former front lines and classified the land into four tiers based on damage. The worst category, the Zone Rouge (Red Zone), was defined as “completely devastated. Damage to properties: 100%. Damage to agriculture: 100%. Impossible to clean. Human life impossible.” It originally covered more than 1,200 square kilometers, roughly 460 square miles, stretching across northeastern France.
Within this zone, entire villages had been erased. Not damaged or burned, but physically ground into the earth by years of continuous shelling. The French government officially declared some of these “villages détruits” (destroyed villages) as permanently dead. A handful exist today only as names on a map and small memorials marking where a church or town hall once stood. The villages that could be rebuilt took roughly a decade to reconstruct, with many residents not returning to anything resembling normal life until the late 1920s.
The Zone Rouge has shrunk considerably since 1918 as remediation work reclaimed land piece by piece. But small sections remain restricted. Near the former battlefield of Vimy Ridge, for example, an approximately 15-hectare stretch of forest on the site’s western edge has been essentially closed to the public since 1918. It still contains unexploded ordnance, human remains, tunnel entrances, mine craters, and trenches.
Filling In and Farming Over
Outside the most devastated zones, the most common fate for a trench was simply to be filled in. Farmers returning to their land pushed the parapets back into the ditches, plowed over the surface, and tried to grow crops again. Across large portions of the Somme, Flanders, and Champagne, trench lines that once stretched for hundreds of miles were leveled within a few years. If you walk those fields today, the trenches are invisible at ground level. From the air, it’s a different story. Crop marks and soil discoloration still trace the old trench networks in aerial and satellite photographs, because the soil where trenches were dug drains differently and holds nutrients unevenly compared to undisturbed ground.
The recovery wasn’t quick or easy. Farmers had to clear surface debris, work around buried metal, and cope with soil that had been churned to depths of several meters by shellfire. In many areas the topsoil had been completely destroyed, replaced by a mix of clay, chalk subsoil, and shrapnel. Crop yields in former front-line areas lagged behind the rest of France for years.
What’s Still in the Ground
The single most persistent legacy of the trenches is the sheer volume of unexploded ordnance buried beneath them. Estimates suggest that across the Western Front, roughly 30 percent of all shells fired during the war failed to detonate. That means tens of millions of live shells were left in the ground. Every year, the French Département du Déminage (Department of Mine Clearance) recovers about 900 tons of unexploded munitions. Belgium’s military demining unit, DOVO, defused more than 200 tons in 2019 alone. This annual harvest of old shells, bullets, grenades, and other debris is so routine it has its own name: the Iron Harvest.
Farmers in northern France and Belgium still turn up shells with their plows every spring. The usual procedure is to leave munitions at the edge of the field for scheduled collection by bomb disposal teams. Construction projects regularly uncover larger caches. These aren’t harmless relics. Unexploded shells from World War I remain fully capable of detonating, and bomb disposal technicians have been killed handling them. Some shells contain chemical agents, making them even more dangerous.
Poison That Won’t Go Away
The soil contamination left behind by the trenches goes far beyond buried metal. Years of shelling saturated the ground with heavy metals from shell casings, bullets, and shrapnel. Research across former battlefields has found elevated concentrations of copper, lead, zinc, mercury, and antimony. At ammunition burning sites near Verdun and in Belgium, copper levels in the soil reached over 4,300 milligrams per kilogram, and lead topped 369 milligrams per kilogram. For context, natural background levels for copper in European soils typically fall below 30.
Arsenic is one of the worst contaminants. Used as a toxic agent in chemical weapons starting in 1917, it has been measured at concentrations between 1,120 and 2,595 milligrams per kilogram at former ammunition sites. Even at Gallipoli in Turkey, far from the Western Front, researchers found measurable heavy metal enrichment in the topsoil linked to wartime activity. Around Ypres in Belgium, a study mapped copper contamination across 640 square kilometers of the surrounding province and found a consistent enrichment of 6 milligrams per kilogram above baseline, all attributable to corroding shell fragments still in the soil.
Chemical weapons have left a particularly insidious footprint. Mustard gas and its breakdown products can persist in soil for decades and leach into groundwater. In the German city of Munster, a former chemical weapons testing site, one mustard gas degradation product was detected in groundwater at concentrations nearly 50 times above the environmental quality threshold. Near Verdun, researchers found similar degradation products in standing water pools and groundwater samples. In 2015, traces of mustard gas breakdown chemicals were reported in drinking water wells. Nitroaromatic compounds from explosives and leaking chemical shells add another layer of organic contamination that researchers are still working to understand.
Human Remains Still Surface Regularly
The trenches were also graves. Hundreds of thousands of soldiers killed on the Western Front were never recovered. They were buried by shellfire, entombed in collapsed tunnels, or simply lost in the chaos of battle. Their remains continue to surface during farming, construction, and erosion. When skeletal remains are discovered, military identification programs from the relevant nations attempt to determine the soldier’s identity through artifacts, unit insignia, DNA testing, and dental records. Canada’s Casualty Identification Program, for example, investigates discovered remains and arranges a proper military burial with the soldier’s unit designation. If identification succeeds, the family is contacted and a rededication ceremony is held. If it doesn’t, the remains are buried as an unknown soldier. Under a policy set in 1970, Canadian war dead from before that date are buried where they fell rather than repatriated.
Trenches You Can Still Visit
A small number of trench systems have been preserved, or more accurately, reconstructed for visitors. The distinction matters. Almost none of the trenches open to tourists are truly original. At Vimy Ridge in France, maintained by the Canadian government, the trench system is a careful recreation with concrete molded to look like sandbags and neatly maintained grass. Sanctuary Wood near Ypres in Belgium is one of the closest examples to a genuine preservation, built from the remnants of existing trenches with the original layout intact, though it has been significantly rebuilt and maintained over the years.
For a sense of what unpreserved trenches actually look like after a century, Beaumont-Hamel on the Somme is instructive. The trenches there survive as small, grassy ditches, shallow and unimpressive. They’re authentic but give little sense of what the war actually felt like. In the forests around Verdun, original trenches are visible from the road and scattered through the woods. Wooden posts that once held up trench walls still stand in places, and the zigzag patterns are clearly traceable, but everything has sagged and softened with time. The forest has swallowed them. Trees grow from what were once firing steps, and root systems have slowly pulled apart whatever structure remained.
This is the most common fate of the trenches that weren’t filled in or built over. Left alone, a trench in northern European soil collapses within a few years. The walls slump inward, rainwater pools at the bottom, vegetation takes hold, and within a few decades the trench becomes a shallow, overgrown depression. After a century, only the trained eye or an aerial photograph can pick them out from the surrounding landscape.