Defensive Rewilding: Where Military and Environmental Protection Overlap

Military strategists know that terrain can potentially decide the victor in a battle between defence and offense. Missing from strategy discussions, however, is the fact that defending governments can not only prepare for the terrain they have, but also physically change the terrain to tilt the balance in their favour. In particular, creating forested cover along road margins and in other areas can help defenders ambush and slow down invaders. This defensive terrain also rewilds and benefits defending countries’ environments. For both security and environmental reasons, countries facing potential military invasion should rewild as needed to create better defensive terrain.

Russia’s illegal invasion of Ukraine in 2022 showed the world amazing close- and medium-distance encounters in which Ukrainian defenders ambushed Russian tanks north of Kyiv, utilising forested roadside strips for cover. This was hardly the first time that defenders have effectively used vegetated cover – such tactics have a long history. In the Second World War and with ethical polarities reversed, German defenders effectively bogged down Allied invaders in Normandy’s farmland, using the tall hedgerows (‘bocage’) lining every small farm plot to take out Allied troops and weaponry.

Of course, forested roadsides don’t always exist, and the less-forested eastern and southern parts of Ukraine experienced deeper incursions in 2022 than the mixed forest and farmlands near Kyiv. Even the thin lines of windbreak trees planted in these regions still provide some protection to defenders, however.

The absence of trees in the right places along roads in Ukraine (or any other defending country) lends itself to an obvious action, one that military tacticians currently ignore. An appropriate analogy would be a defending military force, anticipating an invasion, lamenting the lack of a defensive trench in the right location and then refusing to do anything about it. The solution is clear – if you want some tree cover and don’t have it, then grow it. The cover might take a few years to be more effective, but this would hardly be unique in military policy terms.

It’s important to recognise this is not about abandoning entire farmland regions to forests, but rather about growing rewilded margins along roads and other areas. Another reason for doing this is the environmental value societies now place on nature, and the benefits that roadside rewilding can bring. Reduced flooding, reduced pollution, better pollination, carbon storage, more wildlife and wildlife movement, and even improved hunting and forest products could be part of the outcome. Many of these benefits are immediate, creating political and financial incentives for rewilding projects that will also provide increasing security benefits over time.

Rewilding can help defenders in other locations as well as roadsides. Smaller rivers and streams could have their edges reforested. These ‘riparian’ locations have exceptional environmental value, and provide alternative paths for defenders to move around. Tree cover bordering large, navigable rivers creates ambush points and allows concealed haul-outs for small watercraft. Restored wetlands can restrict and channel invading enemy armour to where the defenders want them to be.

Urban environments are already known for having massive advantages for defenders, but the use of ‘green roofs’ – where roofs have small forests on top – would make them even more formidable. Concealed rooftop environments would help urban defenders move more quickly and with better outward visibility than defenders moving room-to-room. Given that defenders receive advantages from both forested and urban environments, the defensive advantage of having forested urban roofs would be considerable.

No policy solution is perfect. There are economic costs to taking land away from agricultural production, although the environmental benefits alone might outweigh them. Artillery can destroy tree cover, but it will still help to prevent rapid movement and surprise attacks, removing important advantages for invading forces at the beginning of a war. And while invaders moving slowly can better avoid ambushes, this naturally comes at the expense of time. Detection technologies like thermal optics and lidar can also help an invader, but they are imperfect, and their use will slow down an attacking force.

Defensive rewilding can apply to other places besides Ukraine – any country bordering Russia or Belarus might consider it. Taiwan, with a fast-growing, subtropical climate, could benefit especially quickly. Even a single year of dense growth can provide some cover to individual troops, with the concealment improving each subsequent year. As a first step, Western military bases could model defensive rewilding onsite, and improve their environment at the same time.

Using terrain for defensive advantage can be more than a passive tactic. Protecting the environment and protecting against invasion can overlap, and possibly help deter an invasion from occurring.

The views expressed in this Commentary are the author’s, and do not represent those of RUSI or any other institution.

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