Evaluating impacts of linear transport infrastructure on wide ranging vertebrates in the Horn of Africa region

Roads are the arteries of modern society, carrying people and goods to connect distant places and fuel economic growth. Yet, for the natural world, these same paved ribbons often act as barriers, slicing through habitats and creating dangerous zones where animals and vehicles collide. In the Horn of Africa, a region known for its vast, arid landscapes and unique wildlife, a massive new network of highways, railways, and ports is being built to link Kenya, Ethiopia, South Sudan, and Somalia. This project, known as the LAPSSET corridor, promises to transform trade and travel, but it also cuts directly through the home ranges of some of the most threatened animals on the continent. The central question facing conservationists and planners is not just whether these roads will be built, but how they will change the fate of the species that call this region home. To answer this, researchers needed to understand two things: which animals are most likely to be affected by the road's presence, and where exactly on the ground these animals are already getting hit by cars.

A team of scientists from the Hirola Conservation Program and the Kenya National Highway Authority set out to map these risks across the entire region and then zoom in on a specific, newly opened stretch of highway to see the damage in real time. They began by looking at the big picture, using data on where endangered species live to see how much of their territory overlaps with the planned transport routes. They focused on 23 species that are considered threatened, ranging from the critically endangered hirola antelope to various vultures and large mammals like elephants and lions. By measuring how much of each animal's home range fell within a certain distance of the road, and weighing that against how close the species is to extinction, they created a risk profile for the region. Their analysis revealed that the impact is not spread evenly; some animals face a much higher threat than others. The critically endangered hirola, which lives only in a small area of Kenya and Somalia, and several species of vulture showed the highest levels of exposure. For these animals, even a small amount of road cutting through their habitat represents a significant danger because they have nowhere else to go.

To move from theory to reality, the researchers turned their attention to a 143-kilometer section of the Modika–Modogashe highway in Kenya, a part of the LAPSSET corridor that had recently been completed and opened to traffic. Between 2021 and 2023, they conducted systematic surveys, driving along the road twice a week to count and record every animal carcass they found. They documented 91 wildlife-vehicle collisions during this period. The data showed that while large mammals like the Somali giraffe, striped hyena, and gerenuk were certainly being hit, the majority of the victims were smaller creatures. Small to medium-sized mammals, such as the African civet and Kirk's dik-dik, made up more than 60 percent of the roadkills. Birds and reptiles were also hit, but only during the wet season, suggesting that their movements are tied to specific times of the year when food or water is available. The researchers found that these accidents were not random; they clustered in specific "hotspots." These dangerous zones were often located near human settlements, road junctions, and areas with shrubland or open grass, where animals are naturally drawn to forage or cross.

The study also looked at what makes a location more likely to be a death trap. The team found that the type of land next to the road mattered greatly. Animals were most likely to be killed in shrubland and open grassland, environments that offer good visibility for drivers but also attract wildlife looking for food. Surprisingly, the distance from protected conservation areas did not save the animals; many collisions happened nearly 50 kilometers away from the nearest protected zone, proving that wildlife outside of parks is just as vulnerable. The researchers also noted that the risk was higher near settlements and road corners, likely because these areas concentrate animal movement or reduce driver visibility. The study did not find a major difference in the number of accidents between the wet and dry seasons for most mammals, but it did confirm that birds and reptiles are only at risk when the rains come.

These findings offer a clear path forward for protecting wildlife while allowing the region to develop. The researchers suggest that simply building the road is not enough; the design must change to save lives. They recommend targeted measures such as installing fences to guide animals away from the most dangerous stretches and building wildlife crossings where the animals naturally try to move. Speed limits and warning signs near the identified hotspots could also reduce the number of collisions. The study emphasizes that the most critical species, like the hirola and the vultures, need immediate attention because their populations are too small to withstand high levels of mortality. By combining a broad understanding of where animals live with precise data on where they are dying, the researchers have provided a blueprint for making the LAPSSET corridor safer for the Horn of Africa's unique biodiversity. The goal is not to stop development, but to ensure that the roads do not become a barrier that isolates populations or drives these rare species toward extinction.