LINEAR INFRASTRUCTURES AND BIODIVERSITY
The proliferation of linear infrastructures is a recent feature of human societies and occurred exponentially since the mid of the last century. Portugal, is no exception and its territory is crossed by tens of thousands of kilometres of roads, railways and transmission and distribution powerlines. It is one of the European countries where the density of paved roads and highways, per capita, is higher. Currently, in the world and in Portugal, these linear structures are a common feature of modern landscapes, and economic and social gains associated with them are recognized by all.
The term biodiversity means the total variety of life on Earth and includes, genes, species, communities, ecosystems and the ecological processes in which they intervene. It is difficult to assign a monetary value to biodiversity. Several teams of scientists and economists have tried to estimate the global value of biodiversity and, in most cases, have reached huge and higher values than those initially suspected. Many even argue that because human survival depends on the normal functioning of ecosystems, the biodiversity goods and services associated with them represent a supreme value which is invaluable.
Linear infrastructures have negative effects on biodiversity. Among the most significant impacts should be highlighted the increase in mortality from collisions with vehicles, trains or powerlines and electrocution; fragmentation and degradation of habitats and the barrier effect on fauna movements. Terrestrial ground transportation corridors are also an effective channel for the introduction and spreading of alien invasive species through the seeds carried out by vehicles. Over the past 20 years, relations between the presence of linear infrastructures and natural communities have been widely studied in order to find solutions that minimize these impacts. Many of the most recently built infrastructures already integrate specific passages for fauna or other adapted structures (for instance culverts) that allow animals to safely cross the roads and railways; fences and other structures that hinder animals access to the road/railways, reducing the risk of trampling; anti perching devices and flyers that reduce mortality by electrocution and collision with powerlines. However, in old infrastructures, not submitted to environmental impact assessments, these solutions are rarely implemented.
Recent research lines test new solutions aimed at alerting and manipulate the behaviour of animals keeping them away from the risky areas. The application of these and previous solutions facilitate the creation of a Green Infrastructure associated with these "lines" making them multi-functional and more sustainable.