Beasts and Barriers: Obstacles along international borders and their impact on land-based vertebrates

by Vadim Kirilyuk

Translated by Alastair Gill

Within the next few years, 4,000 kilometers of impenetrable border barriers and defense fortifications will be built along European borders as a result of Russia’s invasion of Ukraine and tensions between the EU, Moscow, and Minsk. Many of these fortifications will threaten local populations of land-based vertebrates – including bears, wolves, deer, and bison – with extinction, as old migratory routes are disrupted and animals are killed or injured when they encounter minefields, barbed-wire fences, and ditches. In this article, we examine the main threats to wildlife caused by human-made defensive barriers, and how they can be minimized through a sensitive and nature-friendly approach.

The author’s opinions do not necessarily represent the opinion of UWEC Work Group.

This article contains images of dead animals. 

Russia’s invasion of Ukraine and illegal migration (which peaked in 2020) from Belarus across the border into Poland have prompted several neighboring countries to build defensive structures along their borders. Some states have already announced the completion of border fences: Poland and Lithuania have erected barriers along their borders with Belarus; Lithuania, Estonia, and Latvia have done the same on the Russian frontier.

Elsewhere, Latvia and Ukraine are fortifying their borders with Belarus, Finland is reinforcing its border with Russia, and Poland has announced plans to begin constructing a fence along its border with Russia’s Baltic exclave of Kaliningrad. 

Kyiv is also widening its border strip with Russia and Belarus to 2 kilometers and plans to create a whole network of fortifications, including minefields. Construction work has already begun on a concrete wall on the Belarusian frontier, lined by a moat and an earthen rampart. 

All such barriers present a serious and sometimes deadly hazard to wildlife, as local animal populations find their movements restricted and their lives endangered.

Biological need to move freely

Land-based vertebrates typically limit their movements to an individual or group habitat. Migrations across longer distances are largely associated with the dispersal of juveniles instinctively seeking new territory. Small vertebrates – amphibians, reptiles, rodents or insectivores – have modest individual territories whose size depends on the species’ characteristics, whether the habitat is suitable all year round, and the availability of a stable food supply.

Rodents that live in burrows are tied to their homes and roam across areas of less than a hectare. Hedgehogs and squirrels, which do not use a single permanent shelter, require several dozen to several hundred hectares. Larger mammals with more complex behavior, primarily carnivores and ungulates, have much greater individual ranges. An elk needs from 20 to 200 square kilometers, and a wolf living in a pack needs an area from 100 to over 1,000 square kilometers in size. Just as with smaller animals, the size of their territory depends on their metabolic needs, the energy required to cover or defend the area, and the availability of food. If the animal leads a sedentary lifestyle, then an artificial barrier appearing in its territory will quickly become the territory’s new boundary, altering its configuration and reducing its size.

Why do animals try to evade obstacles?

Dispersal occurs in all possible directions and usually there is no acute need to overcome an obstacle that has appeared in the way. Most juvenile animals spread into neighboring areas, but there are numerous examples of highly risky long-distance dispersals into the unknown by solitary animals. A good example is the arctic hare, which surprised researchers in one study by covering 388 kilometers in 49 days. 

In cases where there is no longer sufficient food or water in an animal’s home territory, or it is under unusually deep snow cover, or threatened by an approaching wildfire, then most animals are faced with the need to move to a new area. Among mammals, only burrowing animals can hide underground when threatened – they have evolved to survive this way. All other flightless creatures flee from danger – and for them the presence of barriers in the case of mortal danger reduces their chance of survival. 

The need for dispersal or roaming, seasonal or spontaneous migration, is found in various animal species, but among large land mammals, intensive movements are most characteristic of ungulates. In the past, when ungulate populations were far larger, most species migrated seasonally. The more heterogeneous the habitats and the more pronounced the seasonal differences in living conditions, the more intensively they roamed. Such movements were usually made in large herds, which can still be seen in the example of reindeer, the saiga antelope and wildebeest. In open habitats – tundra, forest-tundra, wooded steppe, steppe, savannah and desert – ungulates would roam or migrate seasonally for hundreds of kilometers. In mountainous regions, they still make seasonal vertical migrations of over tens of kilometers. In summer, the herds climb to alpine meadow uplands, where there are fewer blood-sucking insects. In winter they descend to valleys and floodplains or to the southern slopes of mountains, where there is less snow and food is more available. 

On the move – whether as part of a regular seasonal migration or when spontaneously fleeing a perceived mortal threat – ungulates persistently strive to go in the direction they need, and during mass migrations, these movements are made with even greater urgency. The appearance of an obstacle in their path forces ungulates to look for ways past, causing them to run back and forth along the obstacle and attempt to jump over or break through the barrier. Such behavior, combined with an increase in the concentration of individuals in a small area, absence of watering holes and the trampling of grass and undergrowth, leads not only to the depletion of food supply, increased stress, and a large number of injured animals, but frequently ends in mass deaths.

As a population grows in size, the need to disperse increases, but when a population shrinks, so does the necessity to wander. Each new impenetrable obstacle further reduces the size of a species’ ​​habitat, leading to an additional decrease in numbers. Many populations of large animals, with the exception of those that have adapted to human presence, are close to disappearing.

We may be seeing fewer incidences of mass animal dieoffs, but only because there are few large animals remaining. Animals are becoming more alert, quieter, and moving about less. In areas densely populated by humans, they are restricted to limited habitats and have a higher than normal mortality rate.

In such areas, small islands of suitable habitat protected from additional mortality factors (such as hunting and pollution from agricultural pesticides) can provide short-term sustainability for small groups of large animals. Their long-term survival, however, depends upon the interchange of individuals with similar groups in the vicinity. These “islands of life” must be connected by wildlife-corridors, free of impenetrable and deadly obstacles.

As the climate changes, the pronounced physical fragmentation of individual animals in an area renders it impossible to make the movements they need in order to adapt. The ability to migrate in critical periods not only helps large groups to survive, but entire populations and even species with a very narrow range.

Roads and highways 

Before examining the influence of border structures, let’s look at the barrier effect of major roads, whose deleterious influence on wildlife is widely underestimated. Busy roads and railroads have a deterrent effect, hindering the dispersal of some species, facilitating the dispersal of other species that use human-made routes, and altering the structure of animal communities. Most importantly, they are an additional cause of death, and constant encounters with vehicles can even lead to the complete disappearance of small vertebrates in the strip bordering a highway. 

The direct deadly impacts of roads can be reduced by lining them with additional concrete or metal fencing. Such barriers reduce the frequency of deadly encounters with traffic for animals of all sizes – while they are not insurmountable, they do obstruct movement. As road networks become ever denser and impenetrable barriers appear one after another, species’ ranges and population groups become fragmented, leading to the gradual extinction of an increasing number of isolated groups.

Incidentally, many smaller animals are killed on rarely used roads. Located in areas little disturbed by human activity, where natural habitats are filled with biota, these roads do not present a barrier effect and deplete populations relatively slowly, but nonetheless kill a significant proportion of individuals from year to year.

On busy highways, fences are erected along the roadway to reduce the incidence of anthropogenic mortality, only reinforcing the role of roads as barriers. The problem can be alleviated by the creation of tunnels or bridges for wild animals. The most effective of these are wide bridges – ecoducts – over a recessed highway or viaducts on high pillars. The introduction of methods for mitigating the deadly impact of highways and disruption to the movement of land-based vertebrates is becoming common practice in different parts of the world, and this is often reflected in changes to national building standards. However, there is still a long way to go.

Border structures

Border structures should be seen as additional obstacles in a network of artificial barriers, separating natural habitats. However, these function not only as mechanical obstructions, but are often the cause of injury and death for animals.

The longest border fences are built using wire or mesh. For wild animals, certain elements of the fences and engineering systems used in the layout of international borders pose the greatest danger. These include barbed wire (including razor wire), tanglefoot wire arrays, fences arranged in several consecutive rows, high-speed roads for the use of border patrol vehicles, high-voltage electric fences, minefields, and partially flooded ditches with vertical walls.

Mines are designed to kill and injure human beings, so the risk they present to animals capable of triggering them needs no explanation. The probability of an animal being hit by a border detachment vehicle or being injured on a fence is far higher if the road is lined by fencing on both sides. Electrified metal fences are a clear danger to land-based vertebrates, while birds are also at risk if they land on electrified wires not far above the ground. A steep-sided ditch partially filled with water becomes a deathtrap for almost all small and large vertebrates that fall into it.

Barbed wire presents the greatest risk to ungulates. The sparse, slender wires give the illusion that they can be pushed apart like branches of a tree. When an ungulate tries to slip through on the run or crawl slowly between individual strands, the animal receives multiple cuts and wounds. In some cases they may end up getting caught on the barbed wire and eventually starve, unable to detach themselves. 

An additional restraining effect is caused by concertina wire, which is deployed on the ground along fences or walls. The thin, soft wire clings to the legs and drags after the animal even when detached from the main coil, ultimately resulting in its complete exhaustion. Multiple rows of linear barriers can be a fatal trap for ungulates, with each successive fright leading to fresh injuries and ultimately death.

War builds barriers

In Ukraine’s Volyn region, work recently began on a concrete and metal barrier fence along the border with Belarus. Such barrier carries no threat of injury to wild animals, but gaps need to be left for numerous small vertebrates to pass through. These can range from reptiles and amphibians to hedgehogs and hares, requiring gaps of at least 8-10 cm. Looking into the future, Kyiv has announced plans to create a no-man’s land two kilometers wide along the frontier, featuring trenches, earthen ramparts, and minefields. Fortifications are also under construction on the other side of the border in Russia and Belarus. 

Barrier mitigation during the design stage 

If a fence has small openings at ground level, then most terrestrial vertebrates will easily pass through the obstacle. For medium-sized and large mammals, however, such barriers can be insurmountable, separating the borderlands of the Ukrainian forests and forested steppes from the vast forest zone of the Eurasian continent beyond.

With thoughtful planning and implementation it is possible to reduce the negative impacts of barriers for wildlife. By placing barbed wire only along the top of a barrier and avoiding the use of barbed wire or concertina wire below a height of two and a half meters, one can eliminate many of the injurious threats to animals. Additional strategies can reduce wildlife mortality, including avoiding the use of water-filled moats, impermeable vertical walls, hazardous electrified fencing, installing perches for birds along the top of fences above any barbed wire, and cordoning off minefields using a harmless additional barrier to block entry for large animals. Other remaining threats – for example, from high-speed roads along the border – are manageable.

Using the above strategies and combining them with additional well-thought-out measures, a natural belt of forest or meadow, stretching for 2,000 kilometers and bounded from the north by a barrier, would be created.

Brushland and steppe wildlife communities will form in areas where trees must unfortunately be removed to improve visibility for enforcement purposes. On the other hand, introducing haymaking and or the regular clearing of undergrowth can be a fertile ground for the introduction of many introduced species.

In other words, it is possible for Ukraine to design and to build border fortifications according to wildlife-friendly principles, reducing the potential for harm to the equivalent of a major road lacking adequate protective infrastructure.

Long-term negative effects of border barriers

Despite mitigating measures, border barriers absolutely do negatively impact the free movement of land-based animals, short and long-term. Impacts include harm to the genetic diversity of a species, lost access to food sources, and landscape damage. Local populations of elk, red deer, wild boar, European roe deer, wolves, and several other large species of mammals will no longer be replenished from the north. It is important to prevent further fragmentation of the Ukrainian populations of these species as well as their habitats and to monitor the threat of a decrease in genetic diversity. If minimal conservation requirements are ignored when construction begins, a line of Ukrainian border fences and fortifications could inflict serious ecological damage on the country’s – and the continent’s – wildlife. In the future, there would be an inevitable need for high-cost infrastructure reconstruction and compensatory measures.

On the positive side, such a border zone could be used to create the planet’s longest nature reserve. It could have limited nature management requirements and a conservation status as a reserve or refuge, with extended areas with intact natural habitats – river basins, lakes, individual areas of woodland, etc. A border zone protected area could become a zone of increased biodiversity with a high reproduction rate, despite the barrier effect for some species. 

Russia’s war in Ukraine and the rise in tensions that preceded it have resulted in the creation of a barrier bisecting Eastern Europe. The need to rapidly fulfill defensive tasks means that these boundaries are often built without attention to environmental requirements and are currently inflicting enormous damage on nature. The more continuous and multi-layered these border structures become in the future and the longer this linear infrastructure exists, the greater the threats to nature. 

As the conflict decreases in intensity, border structures should be created or rebuilt to account for the needs of wild animals and natural habitats in general. Most importantly, the aim should be to ensure that living organisms do not perish en masse as a result of contact with man-made infrastructure.

This planet and humans have a wealth of experience in overcoming challenges of this sort and even in turning them to good use. One way of doing this is to create an additional chain of artificial, natural habitats, shielded from people, supporting the biodiversity and functionality of adjacent ecosystems.

Vadim Kirilyuk is a zoologist, specialist in mammal preservation and wildlife conservation.

Main image source: Tampa Bay Times

More articles on this subject:

• Protected areas and border zones in Ukraine: How to harmonize them? by Oleksii Vasyliuk
• Can the Iron Curtain Be Green? Europe’s nature is being divided by fences and fortifications by Oleksii Vasyliuk and Vadim Kiriliuk