Biodiversity denotes the combined variety of living organisms, ecosystems, as well as the processes that link species and ecosystems. Mobility is such a critical process. It is essential for the survival and well-being of life on Earth as it connects species and ecosystems. Mobility enables organisms to access resources, habitats, and reproduction. It also allows them to escape from threats, adapt to environmental changes and recover from declines and local disasters. This applies to nature as well as to people. Just as cities, economies and markets need to be linked through the movement of people and goods, so are wildlife populations and ecosystems connected through the movement of species.
Human mobility depends increasingly on facilities and infrastructures that provide safe, reliable, fast, and efficient transport. However, modern transport infrastructure such as roads, railways, canals, or airports, are hostile to wildlife, disrupt many of the ecological processes by creating movement barriers and inflicting death to many species that try to cross.
Providing mobility for people while maintaining mobility for wildlife is key to sustainable transport infrastructure. Safeguarding ecological connectivity across infrastructure networks is a central challenge for the transport sector and is increasingly reflected in strategic policy documents and technical recommendations.
Moreover, infrastructure and its traffic affect adjacent habitats and ecosystems by pollution and other disturbance factors that extend into the surrounding landscape. The combined footprint of these impacts goes beyond the physical space occupied by the infrastructure and may cause secondary and cumulative effects that transcend the responsibility of the transport sector. Addressing these impacts requires long-term collaboration amongst various stakeholders and specialists. It also requires practical solutions for local problems that are rooted in that can also contribute to global strategies for mitigation.
Basic understanding of the primary and secondary, direct, and indirect effects of infrastructure and transportation on nature is fundamental to design appropriate mitigation measures (as outlined below).
Primary ecological effects are produced by the physical presence of infrastructure, its structural design, maintenance, and use (see Section 1.3 – Primary effects).
Secondary effects derive from interactions among primary effects, and the interplay with environmental conditions and other driving factors at a landscape or regional level (see Section 1.4 – Secondary and cumulative effects). They typically relate to larger areas and longer time frames than primary effects.
Direct and indirect effects are not synonyms to primary and secondary effects, but simply denote whether observed impact is directly caused by an action, or if it is mediated through the interplay of several actions (e.g., decline in bat populations due to increased vehicle collisions caused by changes in hunting behaviour after installation of streetlights that attract insects upon which bats prey).