The tender heart of a construction maniac: leaving a corridor of life in the natural habitat - wildlife corridor

With the continuous development of human civilization, railways and highways have become an indispensable guarantee for population mobility and economic development, and can be called the "blood" of human social development. While the transportation network is constantly improving, a series of negative ecological impacts brought about by road construction are attracting more and more attention.

What are the impacts of road construction on wildlife?

"To get rich, build roads first" is a slogan known to every household in China. It has become a true portrayal of China's road construction and economic development since the founding of the People's Republic of China. According to statistics, by the end of 2020, the total mileage of railways in China reached 146,000 kilometers, of which high-speed railways had reached 38,000 kilometers, and the total mileage of highways in China had exceeded 5 million kilometers, of which highways had reached nearly 150,000 kilometers. Due to terrain restrictions and traffic needs, many roads and railways need to pass through wildlife habitats. The extensive road network has fragmented the homes on which wildlife depend for survival. The construction and operation of these roads have divided the large areas needed for animal life into small areas, thereby destroying the habitats, growth, reproduction and activities of animals, and also have varying degrees of impact on the foraging, migration, reproduction and other activities of animals.

Figure 1 A family of brown bears crossing the highway in search of food

The living and activity radius of large mammals is often tens or even hundreds of square kilometers. Fragmented habitats cannot meet their basic survival needs. Image from National Geographic Magazine

The most direct impact of vehicles on the road on wildlife is the death of wildlife caused by collisions. According to incomplete statistics, in the past 30 years, as one of the countries with the most developed highway construction, the number of animals (including birds) killed by vehicles in the United States each year has exceeded one million. Globally, the number of animal casualties caused by collisions between cars and trains and wildlife has exceeded that of illegal hunting, and even poses a serious threat to the maintenance of some endangered animal populations. In addition to the significant impact on medium and large mammals that are of high concern, closed roads and high-speed vehicles are almost insurmountable for those slow-moving amphibians and reptiles with seasonal migration characteristics, which also causes these species that are usually ignored by us to become extinct at an alarming rate.

Figure 2 A colubrid snake was crossing the road and was run over by a car. A yellow weasel risked its life to eat the dead snake and was hit and killed by a car that came later. Photo taken by the author on National Highway 108 in Qinling Mountains

In addition to vehicle collisions, noise pollution and light pollution are also major aspects of the impact of railway and highway operations on wildlife habitats. The noise generated by vehicles passing by will scare the wild animals living nearby and drive them away from the railway or migrate elsewhere, further compressing the activity space of the population. At the same time, the lights of vehicles driving at night will also interfere with the foraging and migration activities of nocturnal animals. According to statistics, 83% of the land area of ​​the United States and 50% of the land area of ​​Europe are within 1 km and 1.5 km of the roadside. The impact of vehicle activities on local wildlife has been very significant.

Figure 3: A Qinling antelope in estrus tries to cross National Highway 108 in search of a mate (photo taken by the author in Foping National Nature Reserve, Shaanxi)

The construction and operation of railways and highways have long-term and continuous obstructions to wildlife activities. Animal deaths caused by collisions have reduced populations, and regional barriers and noise (light) pollution have restricted their spread and migration, and affected the genetic exchange and survival of wildlife populations. The resulting long-term effect is to reduce the genetic diversity of species and threaten the viability of populations of various species in the region and the balance of the ecosystem. It is estimated that by 2050, the global road mileage will increase by at least 25 million kilometers, and will mainly be located in developing countries with rich biodiversity (such as Africa, South America and Southeast Asia). The road traffic construction in these countries in the future will directly affect the global biodiversity abundance in the region and even the world. The resulting ecological and environmental effects have attracted widespread attention from the international community.

Figure 4 The vast majority of the 34 key areas for biodiversity of terrestrial ecosystems identified by the United Nations in 2007 are located in developing countries, 14 of which are in China.

It’s not too late to mend the fence after the sheep have been lost, and wildlife passages have emerged

Since the 1950s, Europe has been concerned about the impact of roads and railways on wildlife populations and the corresponding mitigation measures. In the 1970s, the United States, Canada and other countries successively formulated relevant laws and policies, incorporating environmental impact assessment and wildlife corridor design into the construction of conventional highways and roads through national parks. To date, there are thousands of animal corridors distributed all over the world, mostly in Europe, North America and Australia. Since the beginning of this century, my country's road construction and environmental protection departments have also begun to pay attention to the construction of wildlife corridors. The Henan Zhumadian-Xinyang Expressway, which opened to traffic in 2004, passes through the Dongzhai National Nature Reserve and is the first expressway in China to be specially set up with wildlife corridors. The Qinghai-Tibet Railway, which opened to traffic in 2006, has attracted worldwide attention for its highest altitude in the world, huge construction difficulty and unique ecosystem. It has also become my country's first railway project to design corridors specifically for wildlife migration. In 2012, my country promulgated the first regulation on wildlife corridor design, the "Technical Code for the Design of Terrestrial Wildlife Corridors", which puts forward specific requirements for wildlife corridors. Since then, wildlife corridors have been widely used in China's transportation network construction.

Not only in China, but as a world-renowned "infrastructure maniac", China has also taken the establishment of wildlife passages as an important consideration in the road and railway projects it has assisted in constructing around the world in recent years, fully demonstrating its responsibility as a major country in maintaining the relationship between man and nature and protecting global biodiversity!

Figure 5 The Mombasa-Nairobi Railway, built by China Road and Bridge Corporation, has set up a special wildlife passage in the section crossing Kenya's Tsavo National Park based on the activity habits of animals such as elephants and giraffes.

According to the living habits of wild animals, there are several main types of animal passages, such as upper passages, lower passages, and tunnels. The upper passage is mainly a small bridge built between the trees on both sides of the hills above the route when the highway passes through the mountainous area, or an embankment is built on both sides for animals to pass through; the lower passage is mainly in the form of under the bridge, culvert, etc., which mainly takes into account the functions of engineering and animal passages. There are also examples of bridges and culverts specially set up for animals to pass through; tunnels are also a form of animal protection, but their starting point is mainly to prevent the animal habitat from being affected by choosing to pass traffic vehicles through tunnels. It is worth noting that at first, the form of these passages was mainly based on engineering needs, and they also had the function of animal passages. The connectivity of animal communities was not considered as a major consideration for the construction of bridges, culverts, and tunnels. In recent years, many countries have gradually begun to consider the design and construction of various special passages such as bridges, culverts, and culverts based on the living habits of specific types of wild animals.

Is everything fine once the wildlife passage is built?

A wildlife crossing is not as simple as designing a passage for animals to pass through during road construction. The key lies in how to ensure that wildlife can be effectively utilized after it is built.

The migration of wild animals follows certain rules, so the key to setting up animal passages is to find out the migration and migration paths of wild animals along the route and to find areas where wild animals are relatively concentrated. Therefore, it is necessary to obtain a large amount of long-term observation data to understand in detail the distribution of wild animal communities, population size, breeding and foraging habits, common natural animal corridors and migration routes along the route. At the same time, it is also necessary to investigate as carefully as possible the main factors that affect the distribution of wild animals, such as vegetation, water sources, and topography. After the passage is built, it is necessary to continue to monitor the use of the passage by wild animals for a long time, and take corresponding measures to continuously maintain and transform the passage through analysis and evaluation of monitoring data.

A large number of successful wildlife corridors have been built along the Trans-Canada Highway in Banff National Park, Canada, providing important scientific basis for the construction of wildlife corridors around the world. The key to its success lies in the thorough research of site selection in the early stage and the continuous monitoring in the later stage. Image from National Geographic Magazine

The reason for long-term continuous monitoring is that different types of wild animals have different adaptability to passages. A large number of studies have shown that it takes an average of 3 to 5 years for wild animals to understand passages, from "what is this", to "what can it be used for", and then to bravely take the first step. The adaptation time is closely related to the living habits of animals. Often timid and suspicious animals (such as foxes, wolverines, etc.) take longer to adapt.

The things on the ground are protected, but what about those in the water and in the sky?

In addition to animal passages on the road, fishways in water conservancy and hydropower projects are also very important. Water conservancy facilities such as dams can cause river obstructions, change the hydrological conditions upstream and downstream, and thus affect the migration and reproduction of fish. To this end, scientists and engineers worked together to design fishways specifically for fish passage. Fishways first appeared in France. In 1662, the Béar Province in southwestern France issued regulations requiring the construction of passages for fish to pass up and down on weirs and dams. By the late 20th century, North America had nearly 400 fishways, and Japan had more than 1,000. After entering the 21st century, my country also began to build a large number of fishways to protect aquatic species. Representative ones include the Chaohu Fishway in Anhui, the Shangzhuang Xinzha Fishway in Beijing, the Shiquan River Fishway in Tibet, and the Liusha River Fishway in Qinghai Lake. These fishways have played an important role in protecting local fish resources.

In addition, in recent years, the protection of birds in road construction has also received attention. The Hanzhong Basin is a must-pass place for the Xicheng High-speed Railway, and it is also an important habitat for the national first-class protected animal, the Crested Ibis. Once the flying Crested Ibis hits the high-speed railway, not only will the Crested Ibis die, but it will also pose a great hidden danger to the safety of the high-speed railway. For this reason, Researcher Wu Xiaomin (Shaanxi Institute of Zoology), who once presided over the design of the Tibetan antelope channel of the Qinghai-Tibet Railway, designed a unique plan: special protective nets are installed on both sides of the 16-kilometer line passing through the Crested Ibis Reserve. The high-speed railway also passes through this area in the form of an elevated bridge, with a wide bridge hole set up below, so that not only birds but also other animals can pass freely.

The Crested Ibis Protection Net of Xicheng High-speed Railway is the world's first innovative practice of installing special protection for bird protection during high-speed railway construction. Image from Xinhuanet

The road ahead is long and arduous. Traffic engineering projects that set up wildlife passages play an increasingly important role in meeting the spatial needs of animals, ensuring their safety, and maintaining the continuity of their habitats. We still need to continue to work hard to develop the construction of animal passages in a standardized and scientific direction and achieve the goal of harmonious coexistence between man and nature.