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The Evolution of Greenways in China


来源:中华园林网   发布日期:2006-11-18 浏览次数:
 

1. Introduction

Greenways are considered to be "corridors of various widths, linked together in a network in much the same way as our networks of highways and railroads have been linked" (Fabos, 1995). In terms of their function, Fabos classified Greenways mainly into three categories: ecological Greenways, recreational Greenways and historical heritage corridors (Fabos, 1995), each of which can be clearly recognized in the development of Greenways in the US (Zube, 1995). While Greenway corridors were mainly considered as natural and pre-existent (Fabos, 1995), they can also be completely man-made as seen, for example, in urban boulevards (Walmsley, 1995). While the majority of Greenway concepts and related publications are based on western, especially Northern American experience (see Smith and Hellmund, 1993; Fabos and Ahern, 1995; Ahern, 2002), the history of Greenways in China may provide a further and broader understanding of this concept, even as the Greenway concept originating from the American experience may enlighten the potential and direction of Greenway development in China.

It is assumed that the concept and the evolution of Greenways are closely associated with (1) the form and progress of society, and (2) the geography and natural environment of individual nations.
The long history of centralized systems in China has made its mark on the planning and implementation of Greenways. Prior to the 20th century, mere survivalwas crucial and the top-down approach to planning gave top priority to the production and protection functions of Greenways. Other human uses, especially recreational uses and historical heritage protection, were not well considered.

The Greenway concept has evolved in a very different geographical and environmental setting in China as compared to that in the US. With the majority of the Chinese population living on the most rugged lands, of which only 14% are arable, and about 70-80% of the population depending on agriculture, the amounts of forest, arable land and water per capita are respectively 36%, 13% and 25% of the average world level.

For thousands of years, natural disasters, such as floods, drought, sandstorms, desertification and soil erosion have shaped the land and its people (Figs. 1 and 2). These disasters were worsened by the continuous unwise clearing of forests for rulers' grand palaces and, more recently, the poor policies of the late 1950s and 1960s when great amount of forests were cut during the "iron and steel industry campaign" and "people's communemovement" (Forestry Department, 1999). These natural disasters and poor decisions became triggers for the development of Greenways in China in history as well as today (Fig. 3). Thus, the uniqueness of the geographical and environmental situations in China, plus the social and political processes, provide an explanation of the evolution and formation of Greenways.

In the Chinese context, this paper defines Greenways as a linear landscape with elements of trees and vegetation. In terms of their formation and function, three types of Greenways are discussed: Riparian Greenways, which are associated with water corridors or water edges; Parkways or road Greenways, which are associated with terrestrial transportation systems including highways, railroads, country roads, and streets; and farmland Greenways which run along the boundaries of fields and are associated with agricultural protection.


Fig. 1. Rice paddy on steep slopes in the southwest plateau of China, where are the source of many rivers, Yunnan Province, photo by Kongjian Yu.


Fig. 2. Forest have been unwisely cleared in the mountainous region caused soil erosion, Yunnan Province, photo by Kongjian Yu.


Fig. 3. A national campaign for Greenway planting in China for flood control, soil erosion and sandstorm prevention, photo by Yixing Liu.

2. The evolution of Riparian Greenways

Riparian Greenways are defined here as Greenways along rivers, streams, canals and channels. For thousands of years, Chinese people, like others worldwide, have suffered greatly from flooding on large and small rivers. The planting of trees along waterways has, through trial and error, proved to be effective in preventing floods and safeguarding property and human lives. As recent as the summer of 1998, people around the world watched a dramatic scene on television as a young girl named San San held on to a tree all day and night to survive one of the most serious floods in the Yangtze River in recent history. The tradition of riparian Greenways, thus, began as a reaction to flooding and consolidating riverbank protection and evolved from individuals planting trees and shrubs along river and water channels in a piecemeal fashion to a more and more systematic approach in establishing Greenway systems along drainage ways (Fig. 4). This multifunctional ecological and disaster-prevention system is now considered to be fundamental in controlling floods (She and Wang, 1999). The fear of floods, alongside a feverish increase in urban construction, however, has threatened the integrity of these riparian Greenways. More and more rivers in China are now being channellized with concrete even as trees along riverbanks are being cut (Yu and Ji, 2000) (Figs. 5 and 6).


Fig. 4. Greenways planted along the Wen Yu He river at the our skirt of Beijing, photo by Kongjian Yu.


Fig. 5. Recent destruction of the riparian Greenways for the sake of flood control, urban construction and "city beautiful" campaign (it was taken before channellizing), Kongjian Yu.


Fig. 6. Recent destruction of the riparian Greenways for the sake of flood control, urban construction and "city beautiful" campaign (it was taken when it was channellized), Kongjian Yu.

2.1. The tradition

Though a systematic approach to river and riparian Greenway construction in China started very recently, the tradition of protecting and planting trees along river and water channel banks dates back for thousands of years. In the Zhou Dynasty (1100-770b.c.), it was a law that trees be planted along moats outside each city's wall (The Rituals of Zhou Dynasty), and designated officials were assigned to plant and manage moat Greenways. This law also applied to water channels in the countryside. The rituals initiated during the Zhou Dynasty, like other urban construction rituals, were well adhered to in later dynasties. As early as the Spring and Autumn Periods (770-476b.c.), a famous thinker named Guan Zhi described in his works that shrub plantings along river banks consolidated soil and prevented flood damage.

During the time of the Shui Dynasty (581-618a.d.), thousands of willows were planted along the Great Canal that linked Beijing to Hangzhou, a length of more than 1780 kilometers. During the years intervening 907a.d. and 978a.d., a great Greenway project was realized by the Wu Yue Kingdom in Hangzhou, where more than ten rows of trees were planted along the bank of the Qian Tang Jiang River (Meng Xi Bi Tan, by Shen Kuo, around 1031-1095a.d.). Shen Kuo also recorded that in the years 1038-1040a.d., when a later king cut trees forwood that were planted by his ancestors, floods took over vast productive lands. This immediate experience made people understand the function of river Greenways in flood protection.

The Yellow River is well known for its frequency of disastrous floods. In the year 927a.d., after serious
flooding that caused huge damage to the capital, Kai Feng, an emperor of the Song Dynasty, ordered native trees, such as elms and willows to be planted along the YellowRiver. More specifically, the minimum numbers of trees planted were required according to the ranks of government individuals. This ranking was broken into five categories, and the highest ranked officials were required to plant a minimum of fifty trees, while officials of lower rank had to plant forty, etc. Citizens were also always encouraged to plant more trees (The Collection of Orders of Song Dynasty).

This 1000 year tradition of planting trees along rivers has lasted until this century, from Dr. SunYatsun, the first president of the Republic of China, to Chairman Mao Zhedong of the Communist China, and more recently Deng Xiaoping and Jiang Zeming. Top national leaders have always paid substantial attention to flood control and the construction of Greenways along the rivers (Xiong, 1989, p. 83-84; Forestry Department, 1999).

2.2. The drainage Greenway systems

In the 1980s, the state government recognized again the importance of major drainage Greenway systems in the protection of national lands from the threat of flood and soil erosion (Figs. 1 and 2). Five major drainage Greenway projects were officially initiated by the central government. These drainage Greenway systems, evolving from river and water channel Greenway systems, play a critical role in the construction of Greenway networks at the national scale.

2.2.1. The mid- and -upper reach Yangtze river Greenway project

The Yangtze River is the longest river in China, 6300 kilometers long. Its watershed area covers 18% of China with an area of 1.8 million square meters. One third of the nation's population lives in this drainage. Due to dense population and the over cutting of forests, however, the ecosystem has became very fragile. Eroded land area has increased from 36,000 square kilometers in the 1950s to 56,000 square kilometers in the 1980s. Erosion still increases by 5 to 7% annually (Forestry Department, 1999). Flood and drought are still a serious threat to people living in this area. In April 1986, because of this, the National Congress passed the Seventh Five Year Plan, which states that, "forestation should be carried out in the mid and upper reach of the Yangtze River for water and soil conservation". To meet this request, the Forestry Ministry proposed a master plan for constructing a Greenway. It planned for 20 million hectares of forest to be grown in 30-40 years. This plan is to be realized in two phases, one before 2000 and one after 2000. When this plan is realized, a network of Greenways will be constructed along the mid and upper reaches of the Yangtze River drainage area. The project began in 1989 and focused on ten critical areas, which were mainly along river stems and mountain areas. By the end of 2000, it was reported to be a great success with more than 7.4 million hectares of forests reportedly planted covering 20 to 29% of the target land area. The frequency of floods and soil erosion decreased significantly (Forestry Department, 1999).

2.2.2. The Huihe river Drainage Greenway system

The Huihe River Drainage System covers 13% of arable land in China, supports 1 eighth of it's population, and has been frequently flooded throughout history. In 1992, the Forestry Ministry proposed a master plan for the construction of a Greenway system for the whole drainage area, which covers 264,000 square kilometers and accounts for 2.75% of national land. For this 10 year program about one million hectares of forest will be planted. Ten critical projects were also supported in this plan along river stems and mountain ranges suffering from severe soil erosion. This program was put into action in 1995. By the year of 2000, 300,000 hectares of trees had been grown and it was reported to be effectively mitigating the threat of floods and soil erosion in the region (Forestry Department, 1999).

2.2.3. The Mid Reach Yellow River Drainage Greenway System

As the second longest river in China, 5464 kilometers in length and covering an area of 750,000 square kilometers, the Yellow River is considered to be the mother river of China. Its floods and erosion define Chinese history. 78% of the total watershed area suffers from severe soil erosion with an annual loss of 1.6 billion tons of soil. In 1995, the State Council approved the plan for the construction of Greenways along the mid section of the Yellow River. This program covered an area of 320,000 square kilometers and included 26 tributaries along the Yellow River. According to this plan, 3.15 million hectares of trees were to be grown in 15 years from 1995 to 2010. Upon its realization, forest coverage in the watershed will increase from 15 to 25%, and the total area suffering from soil erosion will decrease by 12%. It has been reported that by 2000, 320,000 hectares of trees had been grown, and positive effects in the reduction of soil erosion had been observed (Zhang, 1997; Forestry Ministry, Unpublished Source, 1993, 2000).

2.2.4. The Liao He river drainage Greenway system

The Liu He River, one of the world's seven largest rivers, is in northeast China. Its drainage covers an area of 235,700square kilometers. Because of the unwise cutting of forests along the river, once high quality lands are now suffering from severe soil erosion. In 1995, the State Council approved the master plan for the construction of a Greenway system along the Liao He River. In 10 years (1995-2005), 1.2 million hectares of forest will be grown. By 2000, it was reported that 100,000 hectares of forests had been planted (Forestry Department, 1999; Forestry Department, unpublished Source, 2000).

2.2.5. The Zhu Jiang river drainage Greenway system

The Zhu Jiang river, composed of three rivers in South China, including the West river, the North river
and the East river, covers an area of 442,100 square kilometers and accounts for 4.6% of the national land. It is the second largest river in China in terms of water flow. Due to heavy deforestation since the 1950s, soil erosion in this area increased dramatically and rock exposure increased 3-6% annually (Figs. 1 and 2). In 1993, the Forestry Ministry proposed a master plan for the construction of Greenways along the rivers. The State Council approved this five-year plan in 1995 to grow 1.2 million hectares. By the end of the program, forest coverage in this area will increase from 35 to 38%, and it is expected that soil erosion will be largely controlled. This project has been reported to be progressing slower than expected (Forestry Ministry, Unpublished, 2000).

3. The evolution of Greenways along transportation corridors

Parkways or Greenways along transportation corridors are defined as Greenways along streets, roads, railways and highways. Chinese cities are famous for street trees. The tradition of planting trees along streets and roads dates back more than 2000 years. Providing shade and shelter against wind, and protecting roads from flooding or other damage have been the main functions of this type of Greenway. Visual and perceptual functions were also one of the main reasons for parkway construction. In the long history of road Greenways in China, readers will recognize the evolution from capital streets and imperial highway trees to railroad Greenways to recent green corridor systems along highways because all are linear landscape elements. At the same time, feverish urban construction and the city beautiful movement following the import of Baroque style from Europe and America have turn road Greenways into cosmetic avenues (Yu and Li, 2003).

3.1. Greenways along capital streets and imperial high ways

The first recorded constructed Greenway dates back to the Zhou Dynasty (1100-770b.c.). According to Zhou Li (The Book of Zhou Rituals), street tree plantings became state law and special officials were assigned to be in charge of planting and managing street trees, together with managing wells and hotels along the roads across the country and between cities.

In the year of 221-207b.c., emperor Qin Shi Huang, the First Emperor of China, conquered the other six nations and unified China. Together with a unified currency, language, weights and measures, national highways were built as a measure to control a unified country. Trees were planted along these national highways according to specific standards and two rows of pines were planted in the middle of the highway to define a special corridor used only by the emperor, which was 10 meters wide (Han Shu, The Book of Han, 206B.C-220a.d.), (Fig. 7, Liu, 1981, p. 1).


Fig. 7. The section of Greenways along the National Highway and royal pass built by Emperor more than 2200 year ago, source, Liu, 1981, p. 1.

By the year 206b.c., the Han Dynasty replaced the Qing Dynasty, and the Qing's capital and grand palaceswere burnt down so that a new capital could be built in Xi'an (Capital Chang An). Xi'an was a grid city, with eight main streets all planted with native trees, such as the pagoda tree, elms, the Chinese pine, and Cypress. Subsequent dynasties following the Han kept the tradition of planting Greenways along city streets, not only in the capital city, but in other cities as well.

One of the most powerful dynasties in the Chinese history was the Tang Dynasty (618-907a.d.), which also had its capital in Xi'An. The Tang's capital was perhaps the most prosperous and largest city in the world, and well managed. It had eleven roads (northsouth) and fourteen streets (east-west), in a rigid grid pattern. All were planted with trees, such as pagoda trees and elms. It was recorded that whenever trees were dying, they would be quickly replaced (Fig. 8). The street Greenways must have impressed Japanese students and ambassadors studying in the Tang capital, because this became the model followed by the Japanese in the design and construction of Japanese capitals (The History of Sino Japanese Exchange, see Liu, 1981, p. 3)


Fig. 8. The section of Greenways planted along the street in the capital Xi'an in Tang Dynasty, source, Liu, 1981, p. 1.


Tree plantings along city streets and country roads were considered as good moral behavior and a blessing to the local people, and state officials were always recognized and memorized for their contribution to the construction of road Greenways. One such example is Zhuo Zhongtang in the Qing Dynasy (1644-1911a.d.). As an army general in Xinjiang Province, Zhou organized the construction of a national road that linked the western provinces. He planted millions of willows along this 1500 kilometers road.

The tradition of planting street trees continued and flourished as China experienced socialism and then communism after 1949. Planting trees became a nation wide campaign. In the 1950s, with the help of the former Soviet Union, a host of new, well-planned cities sprouted up with boulevards of street trees. These street and road Greenways matured and are now one of the most characteristic features of Chinese cities and country sides (Fig. 9; Figs. 10 and 11, Fig. 12). In 1979, the National Congress also officially assigned March 12th as Tree Planting Day. Every year on this date, high ranking to low ranking government officials appear on TV to call for planting trees along roads, in parks and along rivers (Fig. 3).


Fig. 9. Street trees in Beijing, the ancient Chinese capital, pagoda trees are still one of the favorite trees as in tradition, photo by Kongjian Yu.


Fig. 10. Greenways along roads, photo by Kongjian Yu.


Fig. 11. Greenways along roads, photo by Kongjian Yu.


Fig. 12. Greenway along one of the earliest railroad in China, photo by Kongjian Yu.


3.2. Railroad Greenways

When railroads first appeared in China they were considered to be bad for Feng-shui (literally means
Wind and Water, or geomancy, the ancient Chinese art of site selecting and landscape planning), and hundreds of soldiers were reportedly needed to provide protection for those constructing railroads (Edkins, 1872; Eitel, 1873; Henry, 1885; Yu, 1994). Chinese people fought against railroads primarily because they thought their rigid straight lines cut up the natural landscape, destroyed the shape of hills, cut across rivers and damaged ancestral burial grounds.

When railroads were firmly established as part of the landscape, the construction of parallel Greenways became an important issue (Fig. 12). In the late Qing Dynasty, as early as 1904, a 30-year contractwas signed between the National Railroad Department and the Fu He Company to grow trees along the railroads between Beijing and Ying Kou. It was agreed in this contract that the Fu He Company could cut lumber from the trees they planted, while leaving tree roots intact. The Railroad Department retained first rights to purchasing railroad lumber (See Xiong, 1989, p. 209).

In 1907, the Qing government ordered individual departments of the Beijing-Taiyuan railroad, and Beijing-Hankou railroad to plant trees along railways. This order emphasized planting trees in order to consolidate the railroad enterprise even as planted trees provided shade and rawmaterial for railroad ties. Enormous numbers of elm trees were subsequently planted (Xiong, 1989, p. 210). These elms saved many lives during the famine years of the 1920s and 1940s when people ate their leaves and bark to survive.

Following the overthrowof the last emperor in 1911, the government of the Republic of China paid great attention to the protection of railroads. In 1914, a tree nursery of more than 30 hectareswas established to provide seedlings for the Greenways along railroads between Beijing and Hangzhou. When floods again swept over the North China Plain in 1917, railroads were seriously damaged. The Railroad Department then established an afforestatation office and bought a 60-hectares parcel of land to build a nursery to support the planting of Greenways along railroads (Xiong, 1989, p. 210). The main purpose of these Greenways was protecting railroad corridors from flooding as well as lumber production. Lumber was only selectively cut, not clear cut.

In the 1920s and 1930s, a great campaign was launched to construct railroad Greenways. In 1934,
a professor from Nanjing University, Zhou Guohua, was invited to plan the Greenway for the Railroad Department. His plan called for planting 1.8 million trees along the railroads, covering an area of about 2,000 hectares. This Greenway is composed of a mixture of trees, such as Chinese pine, cypress,walnut, maple tree, Chinese date, etc. According to this 30-year plan, about 60 hectares were planted each year, with 3,750 trees per hectare. This great plan came to a standstill with the invasion of the Japanese army in 1937 (See Xiong, 1989, p. 210).

3.3. The National Green Corridor Program: the modern Greenway campaign

In August 1997, after floods, soil erosion, drought and sand storms had increased at alarming rates, the former president Jiang Zeming called for "the rebuilding of beautiful mountains and rivers". In response to this call, the National Green Committee, the Forestry Min istry, the Transportation Ministry and the Railway Ministry jointly announced a call for constructing "green corridors" at a national scale. This was perhaps the largest call ever in the history of Greenway construction in terms of its scale and influence throughout the world. This announcement was also an order to related administration departments, officials and even the army in individual provinces and counties that Greenways were to be built along roads, railways, rivers and streams. It stated that, "the greening of road, railway, river and stream networks is critical in promoting the process of making the landscape beautiful". A nation wide campaign was launched.

In 2000, the State Council delivered "a further call for the construction of green corridors at the national scale" to all provinces and departments of the country. The State Council declared that, "the construction of green corridors is an important strategy for greening the nation," and that, "its main task was greening and beautification along roads, railways, river banks and dams". The goal for the nation was that 60% of existing national and provincial highways, railways, river banks and dams be green by the year 2005, and that all areas suitable for vegetation should be green so that a Greenway network could be formed that was composed of green lines, green knots, and green areas by the year 2010. This Greenway network was expected to improve the natural beauty of the landscape and provide ecological security in cities and countryside.

In this high-level document, the State Council even proposed qualitative and quantitative principles for Greenway plantings. For national highways, provincial highways, and railways, the main purpose of Greenway plantings is soil protection, wind protection and beautification. The width of the Greenway on each side of the road or railway should be 5-10 meters, and, whenever possible, more than 10 meters. The Greenway should be composed of trees and shrubs, as well as a mixture of coniferous and deciduous trees. In arid and semi-arid areas, native hardy trees, shrubs and grasses should be selected. In urban areas, the width of transportation and railroad Greenways should be 30-50 meters on each side, and, wherever possible, more than 50 meters wide. For county and village roads, the Greenway should be 3-5 meters wide on each side, and, wherever possible, more than 5 meters wide. Though these numbers may seem arbitrary from the scientific point of view, they do provide an applicable top-down rule that can be followed up across the nation though the existing political and administrative system.

Clear direction relating to construction, management and financial responsibility for Greenways is also described in the State Council document: The Railway Ministry is responsible for Greenways along rail roads; the state government and provincial government are responsible for Greenways along national and provincial highways; the central government and local government are respectively responsible for Greenways along canals, water channels, rivers and reservoirs that are under their management; and the local government is responsible for Greenways along county and village roads. Wherever areas designated for Greenways are taken over for other uses, new, equal areas of land should be set aside in their stead.

4. The evolution of farmland Greenways

Farmland Greenways can be defined as windbreaks that are grown to protect fields from disastrous winds and sand storms. These are especially common in north China where the cold winds of spring and shifting sand dunes are the primary threat to agricultural crops.(Fig. 13). From individual windbreaks and greenbelts to the formation of a Greenway network, three stages can be recognized in recent history (Chao, 1983; Song, 1998; Jiang, 2000).


Fig. 13. Farmland Greenways (wind breaks) in Northern China planted for the protection of crops from wind, photo by Kongjian , Yu.

4.1. Before 1950s: individual fragments of windbreaks

Isolated stands or fragments of wind breaks have been a common practice in northern China for more than one hundred years (Chao, 1983), where the primary function of isolated wind breaks is the mechanical protection of individual farmlands from desertification and cold or strong winds. This form of Greenway evolved particularly in the arid and semi-arid areas of north China, such as Inner Mongolia, Shan'xi, Henan and Xingjiang Provinces, where desertification and spring winds frequently threaten crops. Isolated windbreaks are grown by individual farmers along the boundaries of farmsteads, around the boundaries of fields and along intersecting paths. These windbreaks also served as a source of firewood for individual farmers. Because land was privately owned before the 1950s, these types of windbreaks were not systematically planned, usually small in scale, and located in areas noted for intense winds.

4.2. 1950s-1960s: production oriented&nb, sp;collective windbreak networks

By the early 1950s, after a unified communist country was formed, individual farmers were organized into collective farms and once private fields became collectively owned. The experience of windbreaks in the former Soviet Union was transplanted upon the recommendation of invited experts.Windbreaks became systematically planned and collectively constructed. Primary windbreaks were oriented perpendicular to dominant winds and designed to be 30-40 meters wide with 200-500 meters of separation between rows. This system functioned well and became a characteristic feature on the northeast and north China plain. It was recorded that about 1,700 kilometers of windbreaks were grown in northeast China and 1500 kilometers of windbreaks were grown in Shangdong and Jiangshu Provinces.

There are thousands of kilometers of windbreaks that were also planted in other regions of China. This action was a great success in terms of Greenway development in China and has since proved to be of great significance in protecting fields and increasing yields. These windbreaks also make the Great Plain landscapes beautiful while providing sufficient lumber for fuel.

4.3. Post 1970s: ecological based system of windbreak Greenways

In the production-oriented networks of windbreaks, the goal is protection from, as well as the prevention of winds. After the 1970s, the importance of ecology and ecological systems influenced the planning and design of windbreak Greenways. The land was taken as a system composed of hills, fields, water, forests and roads, and an ecological approach was created for constructing farmland Greenways. These Greenways were not only for wind protection and prevention but the protection of the whole landscape as a system. This conceptual shift resulted in two types of changes in the planning and construction of farmland-protection associated Greenways:

First, the existing windbreak networks were improved by planting additional windbreaks in the grids to increase the density of the former windbreak network and establish a complete network at the regional scale. Among the 635 counties in north China, 10% reported that they had formed a network of windbreaks to cover the whole county.

Second, planning and construction shifted to a regional scale of protective greenbelts. In 1978, the State Council approved the national key project "Three Norths Greenbelt", that covered the North, Northeast, and Northwest of China. In these areas, where most of the deserts of China are located, 1.49 million hectares are suffering from desertification. The size of the area suffering from desertification is greater than the total area of arable land in China. Soil erosion in these areas was also a serious problem; 554,000 hectares suffer from soil erosion. This great Greenway was expected to be a cure to the sickness of this disaster-prone region.

This so called "green great wall" is 4,480 kilometers in length from east to west, 560-1460 kilometers in width, covers 551 counties in 13 provinces. Theses counties all together contain an area of 4 million
square kilometers, and accounts for 42.4% of China. This project, planned in three stages and eight phases, started in 1978 and will end in 2050. In the first phase (1978-1985), 21.7 million hectares of trees were planted. In the second phase (1986-1995), 18 million hectares of trees were planted. In the third phase (1996-2000), 4 million trees were planted. In the coming 50 years and five phases, millions of trees will be planted and grown. At the conclusion of the whole program, forested lands should be increased from 1978s 23.14 million hectares to 58.74 million hectares, and forest coverage should be increased from 5% to 15% of total land area in this Three North area (Li, 1993; Gao, 1997; Zhang, 1997; Chu and Zhang, 1998; Zhao et al., 2000).

This great Greenway project is planned not only for ecological reasons, but also for economic and social reasons. Wood and firewood production is expected to account for most of the economic benefits to the local farmers. This project will significantly increase employment opportunities and make the landscape more beautiful to attract more tourists, as well as improve the security of society.

5. Conclusion

It can be concluded that the concept and evolution of Greenways are closely associated with the form and progress of the society, and the geography and environment of China. Due to its dense population, mountains, relatively insufficient arable land, and a long history of agriculture and cultivation expansion into hilly and arid regions, natural disasters have dominated the lives of individual farmers and government officials in China. The prime factor affecting the evolution of the Greenway concept and Greenway construction in China is therefore the experience of natural disasters, including disasters of winds, floods, drought and desertification. Greenways are ways of securing the land, especially farmland and the people on it, against natural disasters. In addition to these major factors, other factors that significantly influenced the evolution of Greenways in China include:

(1) Changes in society, especially in the 1950s and early 1980s, that altered practices associated with individual ownership of land, agricultural production and organization against disasters.
(2) The role of government organizations and state leaders', such as Dr. Sun Yetsun and Chairman
Mao, calls to promote campaigns against disasters.
(3) The influence of modern ecology, which advanced Greenway construction practices out of a faithbased Feng-shui concept to the experience-based single-functional windbreaks to an ecological system and security network founded on a systematic understanding of disasters.

In comparison with the Greenway concept in the US and its three functions: ecological, recreational and historical or cultural, Greenways in China have great potential and a long way to go. The traditional and current approach to Greenways in China has the following major limitations:

(1) Method: Greenways were mainly planned with a top-down approach with little public participation. This approach is a reflection of the centralized government system, or according to Cosgrove's observation (1998) about social formation and symbolic landscape. The uniformly planned and implemented Greenways are landscape symbols reflecting Chinese social formation. In many ways, the system is very effective. Planning and implementation can be done in a very short period of time or, utilizing a mass campaign, it can be carried out uniformly across the nation. On the other hand, due to insufficient public participation, longterm management may become a serious challenge. This phenomenon is vividly described by the well-known saying that "every year we plant trees, but no trees survive".

(2) Functions: the major functions of the Greenways in China are, so far, protection from natural disasters including wind, floods, soil erosion, and there is little concern for the uses of recreation. This is understandable considering the fact that prior to the 1980s, survival was a to priority for the world's biggest population. Until now, China was predominantly an agricultural country. Prior to the 1980s, only 15% of the national population lived in the city. This situation has changed recently, and very dramatically. By the year 2003, about 37% of the population became urban residents, and this number will rise up to 65-70% in the next 15-20 years. This dramatic change in society will demand a functional shift for the Greenways. Recreational uses will become a major concern for Greenway planning in China, followed by the concerns for cultural heritage and native habitat protection. As commented by Seans (1995), the evolution of Greenways is an adaptive urban landscape that helps mitigate and provides counterpoint to the loss of natural landscape as a result of urbanization. It is expected that the Greenway concept in China will continue to evolve from the protective functions dominated by individual projects to a national Greenway system integrated with ecological functions, recreational uses and historical heritage protection.

(3) The role of science: the Greenway planning and implementation in China has been decisionoriented, more than science based. The role of the Chinese scientific community in making decisions is limited. The sizes and locations of the Greenways are more arbitrary than based upon scientifically based analysis. The arbitrary approach is obvious in the recent national campaign for green corridor construction mentioned in Chapter 2.3 of this paper. Additionally, the greenbelt approach to city planning in Asian mega cities, has not realized significant success (Yokohari et al., 2000). Beijing is in a similar situation. In future Greenway planning and implementation, ecological sciences, especially landscape ecological studies shall play an important role in Greenways planning, as is the case in many other areas in the world.

(4) Misconceptions of "city beautiful": the Chinese landscape is now at a transitional edge due to the rapid and extensive urbanization process. Consequently, Greenway planning and implementation face tremendous challenges. While new Greenways are planned more systematically and extensively across the nation, existing suburban Greenways are facing challenges of being transformed for recreational uses and to create a "city beautiful". Among other misconceptions in urban landscape planning (Yu and Li, 2003), streams and rivers in both urban and rural areas are dammed, channelized and lined with concrete; native trees and plants are cut, cleared and replaced with exotic trees and ornamental flowers. These mistakes, which the Western world had made over the past century, are now being repeated in China.

Though limits exist, there are opportunities for Greenway growth in China. These opportunities come with the coming dramatic changes in the landscapes associated with urbanization. When one considers the current low urbanization level (37%), the likely great urban growth (up to 70% in the very near future), a projected national population of 1.5 billion in 20 years, current low car ownership level (less than 10%) the annual car ownership increase of 30% in cities Beijing and Shanghai, one can easily imagine how much of the land in China will turn into asphalt, and how much of nature's services (Costanza et al., 1992; Daily, 1997) will be demanded by the massive numbers city dwellers.

At this stage of extensive landscape change, China, more than other areas in the world, must adopt a strategic approach to the landscape planning of Greenways. Greenways in China should be planned for the longterm security of the nation and provide natural services the growing cities in a sustainable manner. Considering that land resources are limited and ecological uses often conflict with urban development and agricultural uses, only strategically important points and elements to be set aside to form a security patterns (Yu, 1996). The strategic approaches of the Greenway systems in Boston, Cleveland and other cities in the 19th and early 20th century may provide good examples in this regard Newton, 1971; Zube, 1986). Chinese urban planners especially decision makers should learn from these precedents. China should also learn from the European approaches to urban development (Beatly, 2000) to create greener and more livable cities.

Acknowledgements
This research was generously supported by the China National Natural Sciences Foundation: (1) Ecological security patterns in rural and urban planning in fast developing areas: Theory and a case (#59778010), and (2) The landscape ecological approach to sustainable urban river Greenways (#39870147). Thanks are due to Qingping Ji for her help in preparation for this paper and Douglas Olson for his help in editing.

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Kongjian Yu is currently professor and the dean of the Graduate School of Landscape Architecture, Beijing University, and president of Turenscape (Beijng Turen Design Institute, a landscape architecture and planning firm). Dr. Yu attended the School of Design at Harvard University, and got the Doctor of Design degree. He proposed the landscape security pattern approach to landscape ecological planning, and is the authors of 8 books and more than 100 papers. His current interests include landscape ecological planning in China, landscape security pattern approach to planning for ecological infrastructure. Dr. Yu is also active in practice, his current awarded design project is Zhongshan Shipyard Park (2002 ASLA Honor Award, American Society of Landscape Architects) and Beijing 2008 Olympic Green (Merit Award).

Dihua Li is currently lecturer at the, Graduate School of Landscape Architecture, Beijing University. He got his master of science degree.

 


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