Sustainable urban development in China depends on both the control of pollution and the protection of biodiversity. The importance of the former is now widely accepted, but the latter is still ignored, even by city planners. The wonders of Beijing’s culture are intimately linked with its biodiversity. Central Beijing has 226,000 old-growth trees, and there are 180,000 more in its suburbs. The city is surrounded by rich and diverse ecologies. Baihua Mountain and Wuling Mountain have 1,200 species of higher plants – a natural heritage more precious than any building. London, New York, Paris and Berlin do not have this kind of rich environment. Yet this natural heritage goes ignored.
The planting of trees on urban pavements has not taken ecological factors into consideration and is clearly artificial, monotonous and unreasonably spaced. In city centres, the large numbers of tall buildings and trees lining the streets prevent the flow of air, while in the suburbs more trees are needed. A sad sight, indeed, is the concreting over of the base of the trees, preventing the growth of bushes and grass. The needs of small mammals and birds are not considered. Poplars monopolise the streets of our northern cities – but where are the indigenous shrubs and plants? There is no canopy coverage and lifespan is short, with trees discarded within a couple of decades. There is no consideration of biodiversity.
Cities need to plan for long-term preservation – the older they are, the more valuable. When designing the imperial resort of Chengde, Emperor Kangxi ordered that all existing vegetation be retained. Tragically today’s city planners use only a few commercial varieties, and cities lose their native biodiversity. So some planners turn their eyes to surrounding villages and buy up large trees in great numbers. This means great business for the tree traders, but disaster for trees in rural areas. (In the worst case, rural trees literally fueled the steel-production drive of the Great Leap Forward.) The trend started in Shanghai and spread nationwide, and now almost every city beautification project ships in truckloads of large trees.
One city brought in over 6,400 trees -- each of more than 30cm in diameter -- at a cost of RMB 10,000 apiece. A single tree changed hands for RMB 220,000. Another city purchased large numbers of mature trees from villages and plantations in an attempt to be named a “National Park City” – but before long over 70% of them had died off. A north-eastern city launched a program to transplant 300,000 trees from villages within two to three years. These schemes cause a number of problems.
First, they cause serious damage to rural ecologies and biodiversity. Each tree forms a complete ecosystem with its soil, organisms in the soil, surrounding vegetation and birds, mammals and insects. The amputation of the tree destroys that ecology. Soil and water are lost, animals lose their home – losses that are not worth the benefit to appearance of our cities. The removal of a tree 30cm in diameter also results in the loss of one to two tons of soil. Many older villagers complain that they no longer recognise their birthplace.
Second, huge numbers of trees die during transportation. The cutting of root systems, stripping of leaves and long-distance transportation means 50 to 70% of trees die before they reach their intended destinations. And even if they do survive, what value is there in a mighty tree becoming little more than ornamentation?
Third, the process is part of poorly considered projects which value form over substance. Trees grow slowly. Two decades ago, many specialists suggested tree plantations for future use in cities – but nobody paid any attention, leading to today’s tragedies. Improvement depends of us realising that there is no easy solution; using these large old trees as a quick, green fix is a typical example of projects operated for appearance only. This has led to a lack of tree plantations for the purpose of ornamentation, and those that do exist now have to compete with tree speculators.
Fourth, it leads to corruption and crime. The high cost of bringing trees to the cities mean that there is profit to be made. These large trees have become a commodity, and we now see tree scalpers traveling between villages, seeking a quick profit. Investigations have show that a century-old pear tree can be bought locally for under RMB 100, and a crane to remove it hired for RMB 200 an hour – but get it to the city, and it’s worth over RMB 10,000. Where the money goes is clear. The potential for profit is too high for city officials to resist.
Fifth, the trees bring diseases and pests, which originally were part of a balanced ecosystem where their natural enemies kept them in check. But when the trees are brought into the cities, disease and pest populations explode. This has caused rises in the numbers of various insects in the cities.
Urban biodiversity needs to be approached scientifically. Local ecosystems need to be preserved, with plants selected from surrounding areas to be moved into the cities where they should form self-sustaining communities. Simply trucking in trees is inadequate.
The author: Jiang Gaoming is a professor at the Chinese Academy of Sciences’ Institute of Botany and a doctoral candidate tutor, vice secretary-general of the United Nations Educational, Cultural and Scientific Organisation’s China-MAB (Man and the Biosphere) Committee and member of the UNESCO MAB Urban Group. He is recognised for his introduction of the concepts of urban vegetation and using natural forces to restore China’s ecosystems.