“Is it the road that crosses the habitat, or does the habitat cross the road?” ask scientists before agreeing that the wrong road at the wrong place is bound to cause various perils for the local wildlife, habitats and ecosystems.
“Is it the road that crosses the habitat, or does the habitat cross the road?” ask scientists at Gauhati University (Assam, India) before agreeing that the wrong road at the wrong place is bound to cause various perils for the local wildlife, habitats and ecosystems. Furthermore, some of those effects may take longer than others to identify and confirm.
This is how the research team of doctoral research fellow Somoyita Sur, Dr Prasanta Kumar Saikia and Dr Malabika Kakati Saikia decided to study roadkill along a 64-kilometre-long stretch of one of the major highways in India: the National Highway 715.
What makes the location a particularly intriguing choice is that it is where the highway passess between the Kaziranga National Park, a UNESCO World Heritage site in Assam and the North Karbi Anglong Wildlife Sanctuary, thus tempting animals to move to and from the floodplains of Kaziranga and the hilly terrain of the Sanctuary to escape the annual floods or – on a daily basis – in search for food and mating partners.
In the beginning, they looked into various groups, including mammals, birds, reptiles, and amphibians, before realising that the death toll amongst frogs, toads, snakes and lizards was indeed tremendous, yet overlooked. Their findings were recently published in the peer-reviewed scholarly journal Nature Conservation.
In conclusion, the scientists agree that roads and highways cannot be abandoned or prevented from construction and expansion, as they are crucial in connecting people and transporting goods and necessities.
Sur S, Saikia PK, Saikia MK (2022) Speed thrills but kills: A case study on seasonal variation in roadkill mortality on National highway 715 (new) in Kaziranga-Karbi Anglong Landscape, Assam, India. In: Santos S, Grilo C, Shilling F, Bhardwaj M, Papp CR (Eds) Linear Infrastructure Networks with Ecological Solutions. Nature Conservation 47: 87-104. https://doi.org/10.3897/natureconservation.47.73036
The road is a dangerous place for animals: they can easily get run over, which can seriously affect wildlife diversity and populations in the long term. There is also a human economic cost and possible injury or even death in these accidents, while crashing into heavier animals or trying to avoid them on the road.
Making roads safer for both animals and people starts with a simple first step: understanding when, where, and how many animals get run over. This knowledge can help protect specific species, for example by using warning signs, preventing access to the roads for animals, creating overpasses and underpasses, or closing roads. Wildlife roadkill data can also help monitor other trends, such as population dynamics, species distribution, and animal behavior.
Thanks to citizen science platforms, obtaining this kind of data is no longer a task reserved for scientists. There are now dozens of free, easy-to-use online systems, where anyone can record wildlife collision accidents or roadkill, contributing to a fuller picture that might later be used to inform policy measures.
One such project is the Flemish Animals under wheels, where users can register the roadkill they saw, adding date, time and geolocation online or by using the apps. The data is stored in the online biodiversity database Waarnemingen.be, the Flemish version of the international platform Observation.org.
Between 2008 and 2020, the project collected almost 90,000 roadkill records from Flanders, Belgium, registered by over 4,000 citizen scientists. Roadkill recording is just a small part of their nature recording activities – the multi-purpose platform which also allows the registration of living organisms. This is probably why the volunteers have remained engaged with the project for over 6 years now.
The researchers analyzed data on 145,000 km of transects monitored, which resulted in records of 1,726 mammal and 2,041 bird victims. However, the majority of the data – over 60,000 bird and mammal roadkill records – were collected opportunistically, where opportunistic data sampling favors larger or more “enigmatic” species. Hedgehogs, red foxes and red squirrels were the most frequently registered mammal roadkill victims.
In the last decade, roadkill incidents in Flanders have diminished, the study found, even though search effort increased. This might be the result of effective road collision mitigation, such as fencing, crossing structures, or animal detection systems. On the other hand, it could be a sign of declining populations among those animals that are most prone to being killed by vehicles. More research is needed to understand the exact reason. Over the last 11 years, roadkill records of the European polecat showed a significant relative decrease, while seven species, including the roe deer and wild boar, show a relative increase in recorded incidents.
There seems to be a clear influence of the COVID-19 pandemic on roadkill patterns for some species. Restrictions in movement that followed likely led simultaneously to fewer casualties and a decrease in the search effort.
The number of new observations submitted to Waarnemingen.be continues to increase year after year, with data for 2021 pointing to about 9 million. Even so, the scientists warn that those recorded observations “are only the tip of the iceberg.”
Swinnen KRR, Jacobs A, Claus K, Ruyts S, Vercayie D, Lambrechts J, Herremans M (2022) ‘Animals under wheels’: Wildlife roadkill data collection by citizen scientists as a part of their nature recording activities. In: Santos S, Grilo C, Shilling F, Bhardwaj M, Papp CR (Eds) Linear Infrastructure Networks with Ecological Solutions. Nature Conservation 47: 121-153. https://doi.org/10.3897/natureconservation.47.72970
Common ragweed is an annual plant native to parts of the United States and southern Canada. It’s an invasive species that has spread to Europe. An important agricultural weed, this plant is particularly well-adapted to living at roadsides, and there are several theories why.
Its rapid expansion in Europe can’t be explained by its natural dispersal rate, which is limited to distances of around 1 meter. Rather, there are other factors in play, human-mediated, that support its invasion success – along roads, for example, it spreads mainly thanks to agricultural machineries, soil movements, roadside maintenance and road traffic.
Studying common ragweed’s distribution patterns is important, because its allergenic pollen affects human health, mainly in southeast Central Europe, Italy and France. Finding out where it thrives, and why, can help with the management and control of its populations.
This is why scientists Andreas Lemke, Sascha Buchholz, Ingo Kowarik and Moritz von der Lippe of the Technical University of Berlin and Uwe Starfinger of the Julius Kühn Institute set out to explore the drivers of roadside invasions by common ragweed. Mapping 300 km of roadsides in a known ragweed hotspot in Germany’s state of Brandenburg, they recorded plant densities at roadsides along different types of road corridors and subject to different intensities of traffic over a period of five years. They then explored the effect of traffic density and habitat type, and their interactions, on the dynamics of these populations. Their research is published in the open-access, peer-reviewed journal NeoBiota.
Surprisingly, high-traffic road cells displayed a consistently high population growth rate even in shaded and less disturbed road sections – meaning that shading alone would not be enough to control ragweed invasions in these sections. Population growth proceeded even on roadsides with less suitable habitat conditions – but only along high-traffic roads, and declined with reduced traffic intensity. This indicates that seed dispersal by vehicles and by road maintenance can compensate, at least partly, for less favorable habitat conditions. Disturbed low-traffic road cells showed constantly high population growth, highlighting the importance of disturbance events in road corridors as a driver for common ragweed invasions.
These findings have practical implications for habitat and population management of ragweed invasions along road networks. Reducing the established roadside populations and their seed bank in critical parts of the road network, introducing an adjusted mowing regime and establishing a dense vegetation layer can locally weaken, suppress or eradicate roadside ragweed populations.
Original source:Lemke A, Buchholz S, Kowarik I, Starfinger U, von der Lippe M (2021) Interaction of traffic intensity and habitat features shape invasion dynamics of an invasive alien species (Ambrosia artemisiifolia) in a regional road network. NeoBiota 64: 55-175. https://doi.org/10.3897/neobiota.64.58775