Maintaining grassland connectivity via cars and cows

Many management decisions are based in part on the idea that increased motor vehicles and roads are detrimental to conservation goals.  But what if this type of thinking wasn’t true?  A recent study in Ecography challenges this assumption for grassland ecosystems.  While many plant species historically relied on wide ranging livestock for long-distance dispersal of seeds, the increased fragmentation of grassland habitat has interrupted this dispersal system.  However, the creation of small roads, particularly in rural grassland areas, can potentially maintain grassland habitat through the existence of road verges.  Motor vehicles can potentially replace hooves in carrying seeds over long distances.  Auffret and Cousins put the idea of roads in a novel context by asking whether the rural roads can actually increase connectivity between semi-natural grasslands, both structurally in the form of road verges, and functionally in the form of long-distance dispersal via vehicle tires.  Is it possible that the increased presence of roads, in certain situations, can benefit native plant species and be used as a valuable management tool?

By examining seed composition on vehicle tires (cars, tractors) versus livestock manure (cattle, horse, sheep) in semi-natural grasslands of southern Sweden, Auffret and Cousins determined that vehicles can be effective grassland dispersers.  Samples from vehicles contained a similar number of species compared to manure despite having a smaller overall volume, although there were fewer grassland specialists from the vehicles.  They found no evidence that either vehicles or livestock were major drivers of plant invasion through seed dispersal.  While livestock were able to disperse a higher number of seeds, species, and specialists, the quick and long-distance nature of dispersal via vehicles can be complementary to more natural methods of dispersal. They also found that overall, the rural road network was well connected structurally, potentially enough to maintain a useful level of connectivity between plant populations.  Their results suggest that effective management of road verges could help increase dispersal of native plant species, when used in tandem with more complex management techniques such as rotational grazing schemes.  By maintaining road verges and allowing vehicles to act as replacement dispersers for grassland species, both structural and functional connectivity can be supported through a region.