Survey could help China resolve decline of at-risk animal population
A dead sheep lies beside a national highway in the Xinjiang Uygur autonomous region. (PHOTO PROVIDED TO CHINA DAILY)
A landmark study has gauged for the first time the damage the country's rapidly expanding road network has had on domesticated and wild animals in urban settings.
China has the world's fastest-growing road system, with total mileage reaching about 5.2 million kilometers by the end of 2020, according to the Ministry of Transport.
Our country still lacks national-level research on the issue (roadkill). That’s why we consider our research as kind of a pilot research.
Li Zhongqiu, professor of Nanjing University’s School of Life Science
To date, research in China has mainly focused on "roadkill" in nature reserves, such as the Changbai Mountain Nature Reserve in Jilin province, with limited studies conducted in urban areas where occurrences of roadkill and its impact are more significant.
To address this, Professor Li Zhongqiu and his team from Nanjing University's School of Life Science in Jiangsu province conducted a survey on roadkill in an urban area in China from November 2020 to October 2021.
They reported for the first time the roadkill situation in the megacity of Nanjing, capital of Jiangsu, in a research paper published in PeerJ, an online peer-reviewed and open-access journal, earlier this month.
Roadkill is a worldwide problem. Every year: An estimated 340 million birds are killed on roads in the United States; around 335,000 European hedgehogs are killed on roads in the United Kingdom; and around 9 million medium-sized mammals are killed on Brazilian roads, Li told China Daily.
"These numbers underscore the significant impact of roadkill on animal populations," Li said. "However, our country still lacks national-level research on the issue. That's why we consider our research as kind of a pilot research."
Located on the banks of the Yangtze River, Nanjing has more than 9,700 km of paved roads.
According to their administrative levels, roads in China are categorized as either national, provincial or county. Li and his teammates chose three national highways, three provincial highways and three county highways as their samples.
They ran 26 roadkill monitoring campaigns over 224.27 km of road, totaling 5,831 km during the research period. The nine roads selected for the team's research were monitored every two weeks over the course of a year.
The remains of a nightjar on a road in Xinjiang. (CHEN LIANG / CHINA DAILY)
The team recorded a total of 293 roadkill carcasses. Of the 284 identifiable animals, 136 were mammals, 143 were birds and five were reptiles, Li said.
Birds accounted for nearly half the total, making them the most susceptible group to roadkill, according to the research report. Specifically, cats, dogs and blackbirds were the three most commonly killed animals.
"This may be due to the large number of stray cats and dogs in urban areas," Li said. "Abandoned pets are more likely to wander into traffic."
As a dominant bird species in East China, blackbirds are not only abundant but are also attracted to roadkill carcasses by flies or other insects along the roads, making them more susceptible to becoming roadkill themselves, he said.
May to September were the months in which vertebrates were found to be particularly vulnerable to becoming roadkill, according to the report. The animals' heightened reproductive activity in summer and autumn was cited as a possible reason.
The research found that roadkill incidents for mammals and birds also peaked in November and January. This may be due to the need for some warm-blooded animals, such as weasels, to search for food during winter when food resources are scarce, Li said. As for cats and dogs, which are fully adapted to urban life, their roadkill numbers show less fluctuation between the seasons.
The study provided the first systematic report on the roadkill carcasses of vertebrates in urban areas of China.
However, Li acknowledged that the study is still limited in terms of its data collection and analysis.
He said that the study likely underestimated the number of carcasses, but by increasing the frequency of surveys and conducting more of them on foot, more reliable experimental data could be obtained.
Of the 143 bird carcasses, the species of 90 specimens could not be identified, which made it difficult for the team to accurately assess the impact of roadkill on biodiversity.
"Roadkill has undeniably been a factor in the decline of urban animal populations and must be taken seriously," Li said. "We call on policymakers to implement relevant traffic regulations and animal protection measures, and periodically monitor the effectiveness of these measures to minimize roadkill incidents."
For example, he said, indefinite mitigation measures such as speed limits and temporary traffic controls can be implemented during peak periods of animal-vehicle collisions. For animals such as cats and dogs that frequently use the roads, fences can be erected to prevent them from entering traffic, and passageways can be built to help them cross the roads.
"Finally, we need long-term monitoring of these measures after implementation to determine their effectiveness and make timely adjustments based on actual conditions to minimize roadkill," Li said.
