Woods are hidden ally in flooding and pollution fight
Costly battles to improve water quality, prevent flooding and combat pollution from nitrates and pesticides should enlist a natural and often unrecognised ally – trees and woodland.
Trees are known to absorb carbon dioxide, but their parallel abilities to improve water quality and prevent flooding are sharply defined in a new report commissioned by the Woodland Trust from Forest Research and the University of Newcastle – with a warning that there is no time to waste.
'Woodland actions for biodiversity and their role in water management' analyses world wide literature - the first report of its kind - to highlight the often-unheralded role that woodland can play in overall water management, a role that should be seized upon by water and land managers alike, says the Trust.
The review assesses the impact of trees and woodland on water resources. It spells out how protecting, restoring and increasing native tree cover can help tackle threats posed by climate change, intensive farming and development.
At present 93 per cent of river water bodies in England and Wales, and 45 per cent in Scotland, risk failing to reach their required 'good' status under new Water Framework Directive legislation. The annual cost of removing harmful pesticides and nitrates from drinking water is put at £7 for every water customer.
Woodland creation in the right place can reduce pollution entering water courses by as much as 90% without putting additional strain on water resources, says the report. Sites where ancient woodland is being restored through conifer removal can also reduce nitrate concentrations by up to 90% and increase local water quantity by 20-50 per cent.
As an example, 99% of nitrates draining from arable fields in southern England during winter were retained by the first five metres of woodland planted with poplar trees – with tree buffers shown to also reduce sediment, phosphate and pesticide concentrations.
With flooding continuing to make headlines - and the cost of UK flood risk management put at a colossal £800m for 2010/2011 alone - there is a timely suggestion that creating woodland at bottlenecks on floodplains could significantly reduce major flood events by absorbing and delaying water flows.
In addition simply retaining existing woods would continue to provide a natural prevention measure against small floods, says the Trust.
Richard Smithers, Trust UK conservation adviser and report co-author, highlighted the opportunities of new woodland planted on floodplains. "Scientific models suggest this could reduce the impact of large flood events. There is an urgent need to crack on with field testing and developing best practice."
"If we are to match the rigours of increasingly frequent extreme events arising from climate change, we need to work with the grain of nature, not simply try to control it in an unsustainable way. Considering how long it takes for a tree to grow, the message is that we urgently need to get on with it."
Fran Hitchinson, Trust conservation policy officer, added: "Sensitively sited woodland creation could help deliver the major ecological and chemical improvements required by 2015 under Europe's Water Framework Directive."
"Water managers, planners and water companies need to consider strategic use of woodland which could hold the key to meeting these targets and addressing the challenge of moderating some of the impacts of climate change."
