PARIS — Restoring wild forests, peat bogs and wetlands on Europe’s borders would establish defensive barriers that are hard to cross for enemy armored units, at a fraction of the cost of concrete anti-tank ditches while bringing environmental benefits, researchers said. For tropical coasts, re-establishing mangrove forests could play a similar role.
“Defensive rewilding” combines national security and climate resilience by strategically locating rewilding projects to create natural barriers that impede, delay or channel invading forces, researchers Sam Jelliman, Brian Schmidt and Alan Chandler wrote in an article for the RUSI Journal published on April 7. At the same time, rewilding allows for carbon storage and more biodiversity, they said.
Whereas tactical obstacles such as mine fields or field fortifications are local and temporary, defensive rewilding creates long-lasting “landscape-scale barriers that dictate the geometry of the battlefield before the first shot is fired,” the researchers said. They cited nearly a dozen historical examples of how terrain hinders offense, including during World War II as well as Russia’s invasion of Ukraine.
The concept of defensive rewilding is gaining traction among environmentalists but still needs a “military stamp of approval,” Jelliman, a researcher at the Sustainability Research Institute of the University of East London, told Defense News by phone. “The nearer you are to Russia, the more they think it’s a good idea.”
The researcher said he’s had a number of discussions, including with the U.K. Ministry of Defence, “to sell the idea to people in the military that it’s a viable, useful approach which can have military benefit and environmental benefits simultaneously.”
Defensive rewilding physically changes the geography of potential conflict zones, creating terrain impassible to mechanized forces or channeling them into kill zones, thereby raising the cost of aggression, the researchers said. Meanwhile, a restored peat land or dense forest won’t be seen as threatening and is a way to build up defense without escalating a regional arms race.
To establish a defensive strip of wetland would cost £90,000 to £540,000 ($120,000-$724,000) per kilometer, depending on width, compared to between £1 million and £3 million for a kilometer of concrete anti-tank ditch, according to the report.
Restoring wetlands creates soft ground with low bearing capacity that may not be able to support a main battle tank, while restored water depths would bog down logistics, the researchers said. The bearing capacity of restored wet peat lands is even lower, making them impassible even to light armored vehicles, they said.
The Pripet Marshes in Belarus and Ukraine were a major historical obstacle for German forces in 1941, and “the re-establishment of natural hydrology in peat lands along the Belarus-Ukraine border could be considered a permanent, self-repairing alternative to concrete anti-tank ditches,” the report said.
Eastern Europe in that past had a lot more wetland, much of which has been drained for agriculture, including by the Soviet Union in Ukraine, Jelliman said. That means areas in the north of Ukraine are now drier than they would have naturally been, and easier to move on.
Dried peat bogs would be “quite easy” to re-wet by removing existing drainage channels, whereas then draining them again would only be possible by occupying the hard-to-access terrain, according to Jelliman. Within a year of blocking drainage channels, the water table in peat lands would rise and the ground would become much softer again, the researcher said.
Peat lands “are probably the most challenging to cross, and they’re also probably the most useful from a carbon-sequestration perspective,” Jelliman said. “They’re the primary focus, I would say.”
Rewilded forest creates obstacles that can impede tanks, natural forest clutter is effective against loitering munitions, while dense tree cover can make kinetic projectiles less effective and disrupt line-of-sight for anti-tank missiles. Those effects could “significantly” increase the survivability of defensive positions compared to open terrain, the researchers said.
The researchers cited the Battle of Hürtgen Forest in 1944 as a classic example of dense forest terrain negating the technological and numerical superiority of the U.S. Army.
For coastline defense in the Pacific region, restoring mangrove forests would be “really effective,” as landing craft would get stuck and not have anywhere to land, while the habitat also has high biodiversity value and protects coasts against tropical storms, Jelliman said.
Artificial reefs would be another element of coastal defense, with historical examples in the Pacific Theater during World War II where shallow reefs created obstacles for landing forces, according to Jelliman. Creating reefs would have value for biodiversity, carbon sequestration and storm protection, “and also making it really hard for landing.”
Rewilding rivers by restoring natural paths and softening banks can make them “significantly harder” to bridge with engineering assets, according to the researchers, who cited Ukrainian forces in 2022 using the meanders and forested banks of the Siverskyi Donets River to trap and destroy multiple Russian crossing attempts. Benefits include natural flood control and restoring habitat, they said.
The next step would be for research to demonstrate that defensive rewilding can be effective and practical, and countries such as Finland, Estonia and Poland “are a bit more advanced in looking at that,” said Jelliman.
Defense ministries tasked with contributing to national carbon-reduction objectives are expected to find value in rewilding besides the tactical military benefits, according to Jelliman.
“One of the best ways to do carbon offsetting is to restore peat lands, because they’re quite a good, stable, long-term way of locking carbon away,” Jelliman said. “If they could restore peat lands in locations that are useful defensively, so in large areas of Finland, Estonia, Poland, they could both be a defensive asset whilst contributing to net zero targets and achieving net zero goals.”
With plans for “huge defense budgets” over the next ten years, defensive rewilding allows for simultaneous spending on defense and the environment, according to the researcher. NATO defense spending targets include 1.5% of GDP for resilience, and while what counts as resilience is still being discussed, defensive rewilding might fit the bill, Jelliman said.
‘If there’s any way to make this a cheap way of making borders stronger and more resilient, then that would be good,” Jelliman said.
Rudy Ruitenberg is a Europe correspondent for Defense News. He started his career at Bloomberg News and has experience reporting on technology, commodity markets and politics.
