A safe, just, efficient and environmentally friendly transport system is the ultimate goal of the Swedish transport sector. While safe and efficient are clearly considered as the most important qualities, socially just and environmentally sound are slowly gaining significance and it is understood more and more that a sustainable transport system must include all dice for the game.

It is obvious that construction and upgrading of roads and railroads, cause an increasing fragmentation of natural and human habitat, deprivation of environmental quality and loss of biodiversity, and disruption of ecological processes and social-cultural relations. Transport infrastructure affects landscapes at much broader scale than what can be expected from their physical impact alone - and what is legally considered in planning!


Effects at landscape scale and on ecosystems are substantial - and universal! Practically all countries face similar problems and look for similar solutions. International collaboration exists, but needs to grow in order to address the issues more efficiently (see www.IENE.info). At the same time, political goals for the environment must be translated to operative objectives and mitigation targets for the transport sector. First proposals have been made in Sweden (and Europe), but we still need improved knowledge on cause-effect relationships, critical thresholds and efficacy of mitigation in order to achieve a practical implementation in spatial planning.


There is great need to improve our understanding of the complex pressure of transport infrastructure on wildlife populations and the environment. Authorities urgently ask for adequate methods to predict, evaluate, and counteract adverse effects, and implement this knowledge into the planning and maintenance of transport infrastructure in order to meet sector-level policies on sustainable development and conservation of biodiversity. Mitigation concepts are needed that operate at both strategic and project planning level and can affect the underlying causes as well as the resulting effects and consequences to populations and society. In many cases, dose-effect relationships need to be quantified and potential thresholds identified, before adequate mitigation can be chosen and eventually implemented. Existing ecological knowledge must be combined with economical and social sciences to achieve a holistic approach that allows the whole range of ecological factors operating across the landscape to be integrated within the planning process. This does not apply solely to the planning of transport infrastructure, but likewise to all exploitation and management of natural resources…


Our research focuses on direct ecological effects of roads and railroads on wildlife. We aim at obtaining empirical data and developing methods that can be applied in road planning to evaluate and mitigate adverse impacts.


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Most empirical data on the effects of infrastructure and transport on wildlife refers to primary effects measured at a local scale. Primary effects are caused by the physical presence of the infrastructure link and its traffic. The different types of effects are synergetic, but their relative importance may vary from case to case. In principle, five major categories of primary ecological effects can be distinguished:

Schematic representation of the five primary ecological effects of infrastructure: Habitat loss and transformation; disturbance due to pollution and edge effects; barrier and avoidance; mortality due to traffic accidents and predation; and the conduit or corridor effect. Together, the various primary effects lead to the fragmentation of habitat (COST-341 European Review).


  1. 1)Habitat loss – The construction of roads and railroads always involves a net loss of wildlife habitat. The physical encroachment on the land causes disturbance and barrier effects in the adjacent and wider environment that further decrease the amount of habitat that is suitable or available for wildlife.

  1. 2)Disturbance/Pollution effects – Transport infrastructure disturbs and pollutes the physical, chemical and biological environment. Toxins, edge effects and noise affect a much wider zone than that which is physically occupied. Road and rail verges can represent a trap for predatory animals and forest fires frequently originate here.

  1. 3)Barrier - For most non-flying terrestrial animals, infrastructure represents movement barriers that restrict the animals’ range, make habitats inaccessible and can finally lead to an isolation of populations. The barrier effect is the most prominent factor in the overall degree of fragmentation seen to be caused by infrastructure. Road mortality and the disturbance effect contribute to the barrier impact.

  1. 4)Corridor - Road verges and roadsides can provide new habitats that to some degree compensate for the loss and disturbance of the original habitat. However, the effect can be either positive or negative depending on the context: positive in already heavily transformed low diversity landscapes, non-existent or negative in natural well conserved landscapes where the invasion of non native, sometimes pest species, can be facilitated.

  1. 5)Mortality – Millions of animals are killed on roads each year in Europe. The numbers of road kills are steadily growing, but for most common species, traffic mortality it is not considered as a severe threat to population survival. Some animals, however, are more significantly affected by road mortality than others.

read more:

COST 341 - Habitat Fragmentation due to transportation infrastructure: The European Review. Office for Official Publications of the European Communities, Luxembourg, pp. 31-50. SoA_SE-final2003.pdf 

(c) Andreas Seiler