Wednesday, 19 February 2014

Hedgerows and flooding

With the recent extreme weather and flooding, the function of hedgerows in catchment management has been much discussed in the media. Hedgerows help provide a natural flood defence, to slow storm water run-off from farmland - as shown in these photos taken on and adjacent to Straitgate Farm. A blog "Hedgerows and flooding: rejuvenating our broken and ailing hedgerows network is part of the solution” covers this in more detail. Here are three paragraphs:
The first title for this blog was going to be “Apart from flood mitigation, soil protection, mitigating runoff and pollution of watercourses, hosting natural predators of crop pests, stock management, food, wood fuel and climate regulation, what have hedgerows ever done for us..??” A Hedgelink report summarises the ecosystem services provided by hedgerows, including identifying an important role in water management. 
Evidence points to hedgerows being useful in storing water and increasing its transit time across fields. A 50m hedgerow at the bottom of a 1ha field can store between 150 and 375 cubic metres of water during rainy periods for slow release down slope during dry periods. This effect is greatest in soils rich in clay or organic matter. Because of their deep roots, hedgerows remove water faster from the soil than crops during periods of excessive rainfall, through increased evapotranspiration. 
Since 1945 there has been a drastic loss of hedgerows through removal and neglect throughout the UK, especially in eastern counties of England. Between 1984 and 1990, it was estimated that the length of hedges declined by about 23% in Great Britain. As well as the decline in biodiversity, this loss could present a significant reduction in the services, such as flood management, provided by hedgerows.
How does this affect Straitgate? Aggregate Industries' quarry plans would entail removing almost two miles of ancient hedgerow on slopes above flood-prone Ottery St Mary, at a time when extreme weather and winter rainfalls are predicted to rise. Many people would see that as reckless.