is also where much of the supporting systems, both mechanical and electrical are situated and it is also the area where the men and women who patrol and inspect the network are working. In order for them to see, and be seen by, trains and for them to be able to inspect the track components, this ballasted area has to be maintained largely clear of all vegetation.
Moving out a few metres from the rails, it is possible to move to the maintenance of a grassy sward such that the vegetation is kept relatively low growing and is easily maintained and, perhaps fundamentally, provides a safe area for personnel to stand out of the way of moving trains. It is this area of the railway where many of the signals are found alongside the stanchions supporting the 125kV overhead electric power lines – the safety implications surrounding this equipment are obvious.
Beyond five metres from the tracks themselves, the management requirements are generic and based upon the risk posed by the vegetation to the railway or our neighbours. Removal of this vegetation, or control of pest animals, will be managed on a site specific basis and be dependent on risk assessment.
Invasive or injurious, persistent or pernicious, animal or vegetable, native or non-native? Any organism that attempts to take up residence on the railway infrastructure and, in so doing, causes damage or directly affects safety could easily be classified as one of the invasive species. How much of an impact that species is able to have on the safe running of the operational railway depends on the tools available (manual, mechanical, chemical and biological) and the management decisions taken will determine the level of control, containment or eradication that takes place.
The fact that horsetail (Equisetum spp.) may have been about since the dinosaurs roamed the earth certainly gives it persistence. Its protective waxy cuticle exacerbates this by rendering it near immune to many of the herbicides used on the infrastructure and whilst it doesn’t cause the same issues that its prehistoric tree-sized relatives would have done, nevertheless dense stands are unsightly and impact on the ability to see track components.
Himalayan balsam, as its name suggests, is not native and its explosive seed deployment allow it to invade areas inaccessible to other species, rapid growth and tempting nectaries then quickly create vast monocultures to the detriment of other species, especially those relying on insect pollination.
Seen across the rail network and growing in conditions it is used to in its native Himalayas, buddleia is a common invader and one that causes much damage to structures and budgets alike.
Historical invaders When the railway is not travelling on level ground, it is either passing through cuttings or over the top of embankments. Both the latter expose ground which is often prime habitat for a particular invasive species. Whilst there are often debates about when exactly rabbits were introduced on to these isles, there is no doubt that they are established and thriving in the countryside. Not strictly injurious, although they can inflict a nasty bite, but definitely damaging with burrowing in those embankments causing serious stabilisation issues which can result in multi-million engineering projects to reinstate the slopes. The rodents can also cause crop damage to neighbouring farms, and the cost of implementing control measures needs to be managed.
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