Abstract
Linear transportation infrastructure such as roads and railways is expanding rapidly across steppe ecosystems, creating significant ecological pressures on wide-ranging migratory species.For the Saiga antelope, linear infrastructure acts as a major barrier, fragmenting habitats, disrupting seasonal migrations, and increasing mortality risks through collisions, pollution, and restricted movement, particularly where transport corridors intersect natural river systems.The aim of this review is to critically examine the current state of bridge and wildlife crossing construction materials and designs used in linear infrastructure, including structures that must simultaneously span rivers and maintain terrestrial migration connectivity, with a specific focus on Saiga conservation challenges.The review synthesizes global and regional literature on traditional and advanced construction materials, such as reinforced concrete, corrugated steel, fiber-reinforced polymers, geosynthetics, modular systems, and habitat-friendly surfacing, together with the ecological performance of overpasses, underpasses, culverts, and bridge-based crossings.Additional themes addressed include plastic pollution risks, artificial intelligence (AI)-and machine-learning-based migration prediction, and emerging smart or adaptive infrastructure concepts.The findings indicate that integrated material selection, hydraulic compatibility, and ecological design are essential for crossings that serve both hydrological and wildlife functions yet remain inconsistently applied.