Trees, which act as carbon sinks, should be considered a fundamental part of good urban design.
European forests absorbing less C02 - time for a rethink?
November 5th, 2013
New research shows that European forests are 'peaking' in terms of their ability to absorb carbon dioxide. If this is true, writes Alan Simson, it's time to embrace some novel landscape-scale solutions ...
It's time to take our carbon sequestration duties seriously
Carbon dioxide is a gas that occurs naturally on our planet. But produced in excess, it can cause a great deal of harm - particularly stimulating unhelpful changes in our global climate and national weather.
Vegetation, and particularly trees, are part of a natural process that absorbs CO² and delivers oxygen in return - critical for life on Earth in general, especially for us human beings as we each need 150m² of leaf area to produce enough oxygen per annum for each of us to survive.
Since the industrialisation of our world, and its subsequent urbanisation, the amounts of CO² produced have increased and continue to do so, to the detriment of life on earth. Maintaining - and ideally increasing - the amount of vegetation we have available to mitigate the effects of CO² should be a crucial part of our survival mechanism. However, we may have to re-think how we do this.
Researchers from Wageningen University and Research Centre in The Netherlands have recently concluded that forests in Europe are showing signs of reaching a saturation point in terms of being able to absorb CO².
They cite three main reasons for this - our trees are getting older, and are therefore less able to absorb CO²; urbanism is expanding and the areas of forest and woodland are reducing as a result; and ‘natural disturbances', such as wild fires, are increasing (caused by drought/climate change?), and thus producing yet more CO².
This research seems to fly in the face of the ‘official' view that afforestation across Europe is increasing, and thus able to continue to absorb CO², but on balance I think the research is right. There are a number of reasons for this.
First, as Wageningen suggest, much of our forests are getting on in years and, a bit like us humans, get less active as they get older. Young, energetic and fast-growing trees are best for absorbing CO² - they need it to grow and develop.
It might be useful to differentiate here between commercial forests and areas of woodland - certainly ancient semi-natural woodland. The former was created primarily for commercial purposes and, as far as the UK is concerned, has largely occurred since the establishment of the Forestry Commission in 1919.
The latter is defined as having been in existence since maps and plans were believable - early 17th century in the UK's case - and are thus are often much older in origin, far more ‘ecologically' orientated and very valuable as a result.
There are also management issues. Commercial forestry in the UK has traditionally been managed on a ‘clear fell' system, ie, you plant the trees (usually coniferous), they grow, you thin them a bit, they grow some more, you cut them all down and process them, and then re-plant, usually with the same species. The cycle varies in time-scale, but it is usually 40-60 years.
The general public tend not to like it very much however, as a clear-felled area can look like a World War I battlefield for many years and it creates great change in the landscape. If the public don't like it, neither do the politicians, and it could be argued that due to a lack of political traction, afforestation and re-afforestation in the UK has suffered.
Thus there has been a trend over recent years for foresters to adopt a policy of ‘continuous-cover forestry', whereby only small areas are felled, or sometimes just individual trees, and only small areas are re-planted. Drastic change in the landscape is avoided, but the vigour of a brand new forestry area is lost, and carbon sequestration is reduced as a result. The general public tend to like it however.
Secondly, whilst some urban areas in Europe are shrinking, particularly in some parts of Eastern Europe, much of Europe, and indeed many other parts of the world, are expanding and urbanising at an alarming rate. We are increasing our urban areas in the world by an area the size of Berlin every four weeks.
In the UK for example, the Government wants to build an additional 240,000 houses by 2016, and there is now an increasing cannon of research emerging that suggests that the concept of the ‘compact city' - a theme pursued in Europe for some 30 years or so on the grounds that it is a more sustainable way of developing - is not as sustainable as we thought.
As urban areas expand, they tend to eat into ‘natural' areas, which often contain areas of woodland, and although the woodland is sometimes retained, it can be severely compromised in terms of its function, and thus carbon sequestration is compromised yet again. Such areas can be ‘landscaped' of course, but it is all too often a rather cosmetic response, rather than carried out at a scale that can genuinely replace what has been lost.
If this sounds like a disaster movie in the making, take heart because there are things that can be done to improve the situation. One of the objectives that we have to pursue on our ‘dirty, crowded little island' as Orwell so succinctly put it, is to bring forestry and agriculture back together again to create a form of agro-forestry.
The two land uses went their separate ways way back in the 19th century, unlike in some European countries, but the production of food and timber, together with crucial matters of ecology, amenity and carbon sequestration, have to be a metaphysic for us in the UK - a first principle - and we have to respond accordingly.
There will have to be other changes as well. 80% of the woodlands of the UK comprise only 10 species, and the advent of a raft of pests and diseases that have invaded our land - one of the latest being ash dieback disease - means that we have to greatly increase the resilience of our woodlands and tree planting in general.
This means that we will have to move away from just using off-spring from our local native species of tree and use suitable species from elsewhere. Climate change / warming also means that we will have to start sourcing trees from locations further south in Europe, as trees tend to live for a long time (longer than us) and thus will be more affected by the serious changes in the climate that will be with us before the end of this century.
There is also the issue of creating areas of woodland close to - or even exactly where - people actually live. Thus the rise of the concept of urban and peri-urban forestry has begun to gain ground in Europe. The European Forum on Urban Forestry was formed in 1998 for the exchange of ideas and experiences, and it meets annually somewhere in Europe.
There have also been many EU-funded initiatives over the past decade or so to research and promote the concept of urban forestry, and the FAO has been busily promoting the benefits of urban forestry world-wide. This is beginning to have an effect, as one of the most recent projects - COST Action FP 1204 GreenInUrbs - has delegates from 32 different countries participating!
As well as helping to create good and healthy places to live, love, work and play, urban trees can also assist with providing a carbon sink, especially if planted en masse, which they should be. Now that we can put a realistic monetary value on the environmental, economic, financial, social and human health benefits of trees in the urbs, they have ceased to be merely an urban cosmetic, something to soften the harder aspects of development, and are now a fundamental part of good urban design. As usual, our friends on the mainland of Europe tend to be ahead of us on this, but we are catching up, and the mighty Boris is completely convinced!
As reported by our colleagues in Wageningen, there are discussions taking place across Europe to try to get a measure of agreement in place on forest / woodland management that would try to balance the ecological value of forests with their commercial value and their potential to assist in the mitigation of climate change / carbon sequestration.
As is often the case, Euro-discussions tend to take a long time, and these discussions are no exception, but it is essential that an agreement is reached, and it would be good if that could be concluded by early December this year, as it could be announced at the 2nd European Forestry Week will be taking place from 03rd - 13th December. This will be launched at Metså 2013 in Rovaniemi in Finland.
Such events rarely make the headlines in the UK, but in their response to the Independent Panel on Forestry's Final Report (July 2012), which was commissioned by Caroline Spelman in March 2001, the Government's Forestry Policy Statement (January 2013) clearly sets out a path for future policy on protecting, improving and expanding both public and private woodland and forestry in the UK.
Let us hope that they remain true to their word and that, on this occasion, there is no gap between rhetoric and reality - arguably all too often an unfortunate feature of UK environmental politics. And not before time perhaps, if we are to step up to the plate and not just take our carbon sequestration duties seriously, but re-thinking our whole approach to our environment - not just for the benefit of current generations, but particularly for those who are yet to come.
Alan Simson is a Reader in Landscape Architecture & Urban Forestry, and Director of Research for the School of Art, Architecture & Design at Leeds Metropolitan University. He is involved in research, teaching and consultancy associated with the planning, design, implementation and management of urban trees, green space and infrastructure and associated landscape urbanism, both in the UK and overseas.
He has gained extensive professional experience in the UK New Town Development Corporations, private practice [including his own] and higher education and has been involved with several EU research projects on urban forestry, leading on projects on behalf of the UK Government.
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