Railroad ecology

Railroad beds, like road beds, are designed to drain water away from the tracks, so there is usually a bed of rock and gravel resulting in fast drainage away from the tracks. At the same time, this drainage often accumulates in areas fairly near the tracks where drainage is poor, forming small artificial wetlands. These unnatural conditions combine to form different zones, some in which water is scarce, others in which water is abundant. ==Maintenance==

Railroad companies routinely clear-cut and/or spray with herbicide any vegetation that grows too close to the tracks. This favors vegetation that is able to respond favorably to clearcutting, and/or resist herbicides. On overhead electrified railroad lines, clear-cutting must be more extensive, vertically as well as horizontally, in order to prevent vegetation (especially tree limbs) from interfering with the pantographs on a moving train, breaking off and falling on the wires, or simply from arcing in proximity to high voltage transmission cables. The same vegetative selection processes described in the previous paragraph apply, but may additionally favor climbing vines due to the presence of catenary and transmission poles in addition to the wooden communications and signal pole lines which often exist(ed) along nonelectrified lines. ==History==

Historically, conditions along railroad beds were very different from today. Coal engines used to blanket the area with soot, favoring species adapted to these conditions (some of which only occurred naturally in volcanic areas). Newer engines produced a less remarkable environment, but many of the same plants have remained and adapted to this new environment. ==Invasive species==

Railway tracks (like roads and highways) are often colonized by non-native invasive species. In North America, such species include trees such as Ailanthus altissima, Paulownia tomentosa, Siberian Elm, and Norway Maple, and invasive non-woody plants such as Japanese Knotweed and Phragmites. The railway tracks provide corridors along which these species can spread and thrive, even when the surrounding areas might be less hospitable to them. Many invasive species have been known to be propagated by railways, these include: spotted knapweed, South African ragwort, Oxford ragwort, rat, mouse, ants, beetle, spider, and armadillo. Causes There are three mechanisms that lead to invasive species being spread by the railway industry: • Commodity: when the goods carried by train are the invasive species, which can escape into the surrounding habitat. • Stowaway: when the invasive species is inadvertently transported by train. • Natural dispersion: when the species invades by an artificial corridor such as the railway verge. Railway verges, similarly to road verges, are typically regularly mowed and covered in herbicide by train companies. This creates an environment that is very different from the surrounding habitat, which could be a forest for example. Native species from the surrounding habitat are not adapted to this new habitat type, allowing generalist species and species who favor open environments to take root. These railway verges can extend for multiple kilometers without being interrupted, creating a corridor for species to disperse. Additionally, when constructing a new railway, vegetation is removed, soil is bared, and water is managed, creating ideal conditions for invasive plants to implant. Impacts The impacts of invasive species are widespread. They modify communities and ecosystems making them more vulnerable to disruptions such as climate change. They can outcompete native species and cause their extinction. For humans, invasive species have a huge economic cost. Management There are four main management categories to stop invasive species along railways: the do-nothing strategy, the management of the propagule supply, the management of environmental conditions, and the management of the invasive species populations. The do-nothing strategy is, as its name suggests, to not try to act against the invasive species. This strategy can be appropriate when the cost of management is very high or when a native species will likely overtake an invasive species in future successional stages of the railway verge. Managing the propagule supply can be done in many ways, planting or seeding the verge with native plants and using fire management to burn seeds of invasive species are two examples of this method. Changing the environmental conditions to prevent native species from implanting can be done through soil compaction for example. Removing the invasive species can be done by burning, using herbicides or mechanical removal. Removing new patches of the invasive species should be prioritized when this species spreads fast as this new patch can be a new source of dispersal. Creating barriers for the invasive species to stop spreading should be done for species with lower dispersion speeds. Management practices should always take into account native species to not harm them. == Impacts on local wildlife ==

There are four main impacts on wildlife from railroads: wildlife mortality, the barrier effect, habitat fragmentation/loss, and disturbances. to deer and large mammals such as elephants may be killed in collisions with trains running on railway tracks. Studies on wildlife-train collisions have mostly been focused on moose and bear. These species are large and due to their size, are more likely to cause a financial impact when a train collides with them. Barriers Railways and powerlines to supply electrical trains, like other linear infrastructures, divide habitats when built. == Railway mitigation measures ==

There are many different railway mitigation measures, most of them fit into two main categories: either to prevent animals from being on the tracks or reduce the barrier effect. Measures that allow movement across the railway Structures already built into the railway infrastructure such as pipe culverts, box culverts, small access roads and bridges to cross rivers or valleys can offer safe passage underneath the railway for wildlife. Audio animal calls produced 30 seconds to 3 minutes before the arrival of a train increased the rate and the speed at which wildlife fled, with wildlife not habituating to these sounds. Other mitigation measures Reducing train speed at mortality hotspots or during migration periods can help animals and train drivers see each other earlier, leaving more time for the animals to flee. Selective hunting and trapping near railways can reduce wildlife-train collisions. Construction of rail infrastructure can also be reduced or stopped during critical periods of migration. == Differences between road ecology and railway ecology ==

Railway ecology is much less studied than road ecology. This could be because railways are typically harder to access than roads or because roadkill is much more visible to the public, while wildlife-train collisions are only visible to train drivers. Trains and railways are very different from road motor vehicles and roads themselves. Trains typically are on a singular track, they cannot swerve to avoid a collision and their capacity to slow down is very limited. Trains only come from one direction, while roads are normally bidirectional. Intervals between vehicles are much longer on railways than on roads. Only a singular train comes at a time, while many vehicles are on the same stretch of road at once, often on multiple lanes. Road traffic occurs more often during the daytime, while train traffic can be higher in nighttime. Trains cause more vibrations due to their weight and the interaction between tracks and wheels. There is a large proportion of electrical trains, leading to lower emissions near tracks than gas vehicles on roads. Trains can be much quieter than road vehicles. The size of the railway and its verge is normally much smaller than the size of a road and its verge. High speed trains can be much faster than road vehicles, and fencing is more common along these high speed train tracks. ==See also==