Wednesday, October 26 2016


Under the urban tree canopy

Update: April, 18/2015 - 10:01

 Paul Barber*&Pham Ngoc Dang**

Articles published in Viet Nam News and online have detailed some of the reasons for the recent removal of many of Ha Noi's urban trees, providing some justification for the Government and private companies, and raising concerns and protests from the community and well-intentioned individuals.

We believe it is important to question the science behind these decisions and the future plans of the city's green spaces. Future management of urban green space and canopy cover should be based on science, knowledge and experience.

This article will question some of the points listed in recent articles, provide support for others, and hopefully generate some meaningful and constructive discussion and subsequent actions.

The article is not only applicable to Ha Noi, but all of Viet Nam's cities, as the premature and unjustified removal of large trees in other cities is now occurring and must be stopped for the benefit of Viet Nam's environment and society.

Much discussion in recent articles has centred around the long-term plans for Ha Noi's street trees, parks, gardens and lakes with the aim of ‘improving the urban architecture and environment as well as traffic safety'.

There is a vision for Ha Noi to ‘be built into a green and clean city by 2020'. There is also a plan to slowly ‘increase tree coverage in the city from around 2 sq.m per person by planting 1,500-2,000 trees each year'.

Authorities who have developed these plans and visions should be commended as they have good intentions for the city and the people who live in it. Sustainable urban development is one of the greatest challenges facing mankind. The decisions we make now about planning and management of the urban tree canopy are likely to have serious implications for the environment and societies that rely upon it.

Without having a precise measure of the baseline and using reliable methods to measure future change, you cannot be clear on whether you are meeting the targets that have been set and therefore whether your urban green strategy is successful. We question the accuracy of the existing baseline measure of 2 sq. m/person that has been quoted.

The justification for the removal of many of Ha Noi's large trees is their ‘general poor quality' and ‘unsuitability for urban areas because they are old and have not been cared for properly'.

It is important to question what is meant by ‘poor quality'. Is it the presence of decay, structural defects, low crown vigour etc.? If it is these traits then the age of the tree does not dictate this.

Trees are living organisms that naturally develop over time and adapt to prevent premature failure due to decay and structural defects. It is true that as trees age they may decline in vigour.

However, it is the history of and ongoing management practices that often have the greatest impact on the quality or health of trees.

There are many examples of young, advanced trees that have been planted recently throughout Ha Noi that already have structural defects, low crown vigour and extensive decay or damage. Such trees, if they become established and grow, are likely to become more hazardous and present a moderate to high risk to life and property.

The removal of iconic trees such as the magnificent African Mahogany because they are deemed to be ‘not safe around residents due to their fasciculate roots and susceptibility to failure during typhoon season' must be based upon sound science and assessment by experts, not simply based upon opinions.

The question must be asked about how many people have been seriously injured or killed in Ha Noi over the past 10 years as a result of falling trees? It would be very interesting to compare this to the number of people seriously injured or killed on motorbikes, or the number of people who have died from smoking-related illnesses. We would suggest that the figures for motorbikes and smoking are much higher. Does that mean we should ban motorbikes or smoking of cigarettes to improve safety for Ha Noi's residents?

The benefits provided by these large trees would far outweigh the costs. The reduction in air pollution, the provision of shade, a habitat for fauna, the spiritual connection and well-being of residents, the reduction in noise pollution, the capture of polluted storm-water, and the capture of CO2 and provision of oxygen. In comparison, motorbikes, although essential for transport, produce a large amount of pollution and congestion on the roads, and cigarettes provide no benefits and only damage health.

It has also been stated that ‘the replacement of unsuitable and dangerous trees is necessary to ensure the urban structure and traffic safety, especially trees on the urban railway line like Nguyen Trai and Kim Ma.

Those trees will become very dangerous during heavy rains with strong winds. If a tree falls on the railway line, there can be unpredictable consequences. What are the criteria for the removal and replacement of trees? What risk assessment has been carried out? There are several recognized methods around the world for assessing the risk of urban trees, and options to mitigate these risks.

It is also important to understand the causes of declines in the health of urban trees, how to prevent hazards, and how to mitigate risks. Diagnosis of the cause (s) of declines in the health of urban trees is complex but it is essential for successful management. Over recent years, we have witnessed the premature decline in health of many urban and heritage trees throughout Viet Nam.

We see a completely unsustainable approach that will lead to a great deal of sadness in the future, and a very sick and more hazardous tree population. We also see that many of the replacement trees are totally unacceptable.

This must be stopped and future management of urban trees throughout Viet Nam must be based on sound science, knowledge and experience, not misinformation and fear. There is a great need to adopt new technologies for conducting precise diagnosis, monitoring and management of urban trees to achieve sustainable urban forest management in the future.

* Paul Barber is the Director of ArborCarbon Pty Ltd, Murdoch, Western Australia, Australia and Adjunct Associate Professor, Murdoch University, Western Australia, Australia

** Pham Ngoc Dang is Vice President, Viet Nam Association for Conservation of Nature and Environment, Ha Noi, Viet Nam

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