Going Dutch

I was in Amsterdam for a few days last week and apart from thoroughly enjoying the art and the peaceful ambience of the canals I also came away with an intense admiration for dutch aboriculture and management of urban, roadside and hedgerow trees. Ancient pollards are impeccably maintained as high trees using carefully considered pruning regimes and discrete webs of steel cables. Younger trees are pruned into a variety of spherical or pencil shaped additions to the urban landscape.
In one of the squares I passed through trees approximately 12 feet high that had been pruned to have flat tops reminiscent of how I imagine that the ancient “dancing oaks” of druidic England must have been. The results were visually extremely effective, ensuring that the trees gave a high degree of shelter while casting minimal shadow.
The Dutch government is currently locked into an industrial dispute over wages for the scaffy, and there were substantial mounds of rubbish at most street corners which were slowly subsiding into the canals. Given such apparent financial constraints it is surprising that expenditure on arboriculture is maintained. To a great extent the reason is that in many parts of the country hedgerow trees are regarded as an important asset both in terms of shelter and in terms of production of wood, primarily for wood fuel.
In Scotland there is a great deal of discussion about land availability for woodland expansion. Given that one of the drivers of for this is increasing wood fuel demand it might be worth considering the potential role of hedgerow trees. Trees in hedgerows will sequester as much carbon, if not more given probable site fertility, than their woodland counterparts, and given the probable mixture of species, may have a greater biodiversity value. Moreover, they will burn!
The more hedgerow and amenity trees we plant the less pressure there will be to establish woodlands on organic soils or on productive farmland in direct conflict with food production.
This is not as fanciful as it sounds. A colleague in the northern Netherlands has established wood fuel supply chains based on the 7000 kilometres of hedgerows and wooded banks in the region. He has found that if the trees are pollarded on a 15-20 year cycle it takes approximately 9-16 metres of wooded hedgerow to produce a cubic metre of wood chip. On that basis if a 10 ha field was bounded by hedgerow it would produce 80-140 m3 of wood chip or 4-7 m3/yr.