From Silk to Pavement: The Rapid Development of Roads in China

Introduction

While China’s rapid economic growth has garnered much attention in recent years, its associated boom in road building is neither well-documented nor wellunderstood. With more than 3.5 million km of roadways already in place (CIA 2010, Li et al. 2010), China continues to build roads at an amazing rate. For
example, China’s network of expressways has increased from 652 km in 1992, to more than 65,000 km today (CIA 2010). Such expansive road networks are powerful drivers of regional ecosystem change (Liu et al. 2008), and China’s continued road construction and expansion projects will cause an increasing loss
in habitat (Li et al. 2003), posing a grave risk to terrestrial and aquatic wildlife.

Recent research has found China’s road building to result in habitat fragmentation (Li et al. 2010, Liu et al. 2008), altered wildlife migration patterns (Li et al. 2003, Xia et al. 2007), the spread of invasive species (Ding et al. 2008), soil erosion (Liu et al. 2008), increased impervious surfaces (Elvidge et al. 2007), and an increase in global greenhouse gas emissions due to increased travel and
the quantity of cars. In this paper, I review the ecological consequences of the unprecedented growth of China’s road system.

Habitat Fragmentation

A leading cause of habitat fragmentation in China today is road development. Roads greatly alter an  area’s environment and landscape structure, producing edge habitat (Liu et al. 2008). Such induced habitat fragmentation can pose a threat to the ecological flow of an ecosystem. This may influence many important ecological processes, such as animal movement, water runoff, and erosion (Fu and Chen 2000), gene flow, and sustained biodiversity (Li et al. 2010). Soil nutrients such as phosphorous and nitrogen may be captured and processed differently due to habitat fragmentation. The degree to which these nutrients will be affected depends upon the differing patch types that occur in a fragmented
landscape, along with vegetation and soil conditions (Fu and Chen 2000).

Wildlife Impacts

The expansion and construction of new roads may lead to increased mortality through direct wildlifevehicle collisions, but also through behavioral changes such as road avoidance and disruption in migration and movement patterns. As a result, connectivity between habitats is greatly reduced or
restricted, leading to habitat loss (Li et al. 2003, Xia et al. 2007, Eigenbrod et al. 2008). For example, the snow leopard (Panthera uncia) and giant panda (Ailuropoda melanoleuca) are two such species that researchers have found to be significantly threatened by habitat loss caused by road construction in China (Xu et al. 2008, Zhang et al. 2007). In fact, Zhang et al. (2007) found that, as of 2007, only 100 km2 of suitable habitat remained for the giant panda, down from 1330 km2 in the 1950s, in the Daxiangling Mountains of Sichuan Province. Consequently, only 17 giant pandas inhabit the area, a decline from a population of approximately 50 in the 1970s (Zhang et al. 2007).

Researchers studying the effects of the Golmud-Lhasa highway and the new Qinghai-Tibetan railway on
the Tibetan plateau found that both cut through the summer migration route of the Tibetan antelope (Pan-tholops hodgsonii), also known as the chiru (Xia et al. 2007). Xia et al. (2007) observed that the railway acts as a physical barrier to chiru activity and that the tourists and construction workers traveling or working on the highway and railway negatively affected the chiru, causing the herd to separate and scatter on several occasions.

Invasive Species

China now has more than 250 international entry points (airports, seaports, railway and motorway
stations). This, plus a staggering increase in international trade, has resulted in an increase in invasive species (Liu et al. 2007). Invasive species are detrimental to the environment because invasives may replace native wildlife, reduce biodiversity, and increase the risk of extinction in some species (Ding et al. 2008). Invasive species enter China at one of its many international entry points, and then spread throughout the landscape along China’s growing highway network. By 2005, the amount of destructive invasive species intercepted at Chinese borders grew 10-fold from 1990 levels (Ding et al 2008).

Soil Erosion

Road construction has been shown to cause soil erosion, which leads to further land degradation (Zhang et al. 2006) in the road-affected zone (the distance from the roadway in which impacts are felt
in the ecosystem), and the greater the road density, the greater the risk of erosion. Studying the ecological risk of soil erosion from road construction in the Lacang River Valley, Liu et al. (2008) found that expressways held a medium risk of soil erosion, and that a mild risk was found across all road types.

Impervious Surfaces

China has the greatest amount of man-made impervious surfaces in the world (87,182 km2; Elvidge
et al. 2007). The impervious surface of roads and expressways causes hydrological and ecological
disturbances (Elvidge et al. 2007), including: an alteration in heat fluxes, resulting in increased surface temperature (Changnon 1992); the reduction of carbon sequestration from the atmosphere in previously dense vegetation sites (Milesi et al. 2003); an increase in the magnitude and occurrence of
surface runoff into watersheds (Booth 1991); and changes to the shape of stream channels caused by an increase in overland flow from rainwater traveling more quickly across the ground, which adds pollutants from urban areas into streams and increases water temperature (Beach 2002, Carlson 2008).

Increasing Greenhouse Gas Emissions Due to the vast expansion of transportation networks in China, domestic transport has significantly increased. The quantity of private-use vehicles, which were
formerly government controlled, has increased by 20-fold since 1978 (Ding et al. 2008). More Chinese citizens drive now than ever before such that China’s largest cities now attribute 80% of their carbon monoxide and 40% of their nitrous oxides to motor vehicle emissions (Hu et al. 2010). From 1980 to 2005, total annual emissions in China from methane and carbon dioxide increased by 7440% and 3290%, respectively. Furthermore, China surpassed the U.S. in 2006 as the world’s largest emitter of carbon dioxide, with emissions reaching 7,050 million tons (Mt) in 2008 (Yan and Crookes 2010).

Conclusion

The National Expressway Network Planning of China intends to expand the country’s expressways by an additional 20,000 km by 2025, for a total of 85,000 km (Planning and Research Institute of China 2010). As China continues to add new roads and expressways, the impacts to the environment will only
get worse if the country expands without sustainable planning and development efforts. Sustainable development would include efforts to reduce fragmentation wherever possible, encourage alternative sources of fuel, and promote the use of public transportation. As more China-specific research is conducted, a better, comprehensive understanding of road-induced impacts will reveal the magnitude
of the impact that China’s exponential expansion is having on its environment.

— Monica is a graduate student in the University of Montana’s Environmental tudies Program.

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