Controversial crop or helpful habitat?

The green fields around the Basin are currently divided by great swathes of bright yellow, as the oilseed rape comes into full bloom. The name is derived from rapum which is the Latin term for turnip, and despite its very colourful appearance it is a brassica.

Few crops have caused more controversy. Some people have objected on the grounds that it ruins what they see as the traditional appearance of the countryside with its dazzling colour. Others claim that it causes allergic reactions and physical irritations. The internet is awash with opposing campaign groups and disputed research and I have no wish to add to those debates in this article.

What is beyond dispute is the significance of the crop to British agriculture. Virtually unknown in Britain before the 1970s and the entry of the UK into the European Community, it is now our third most important crop behind only wheat and barley. There were 3,857 hectares of oilseed rape in the UK in 1980 but this year’s figure looks likely to exceed 600,000 hectares, which is a staggering rate of expansion.

The extracted oil is used for cooking and margarines as well as a range of industrial purposes. Recently an increasing volume has been used in bio-diesels. Given this range of uses, and the fact that the processed plant also provides a very useful source of animal feed, it is likely this newcomer will remain part of our landscape for a very long time.

Oil seed rape and rainbow at Montrose Basin (c) Scottish Wildlife Trust
Oil seed rape and rainbow at Montrose Basin (c) Scottish Wildlife Trust

The crop is used by a very wide variety of birds and insects throughout its growing cycle. It is usually sown in autumn, and winters as a low standing green plant resembling turnip leaves. This vegetation can attract hundreds, and sometimes thousands, of woodpigeons to a single field with adverse effects on the crops.

In fields close to Montrose Basin during the winter, the farmers also have to contend with large flocks of  resident mute swans as well as migratory whooper swans which can cause considerable damage to the rape. But not all the winter species pose a threat to the crop. The moist ground below the leaves encourages invertebrates to remain close to the surface and provides feeding opportunities for winter thrushes, finches and other small birds.

The rape grows rapidly in the spring, and by May it is standing about four feet high. The dense lower vegetation shades the ground keeping it moist for invertebrates, and the leaves provide a suitable habitat for spiders and insects. At the head of the plant, the bright flowers attract a range of pollinating species. This wide variety of insect life in turn attracts birds, including some of our summer visitors.

A walk around a rape field this week revealed the presence of sedge warblers, linnets and reed buntings in the crop as well as swallows swooping low, feasting on the airborne insects. The sedge warblers were particularly active, singing loudly, indulging in display flight and obviously holding territory. Most of these sedge warblers will use the crop to feed on its abundant insect life but will build their nests nearby, beyond the field boundary. A minority however build their nests in the crop and are usually able to fledge their single brood before the summer harvesting.

We still have much to learn about the interaction of oilseed rape and wildlife but studies to date have shown that it is beneficial to a wide range of birds. I suspect this fact will do little to dampen the other controversies about its place in British farming.

Dennis McCullough – Montrose Basin Volunteer

Preface

The green fields around the Basin are currently divided by great swathes of bright yellow, as the oilseed rape comes into full bloom. The name is derived from rapum which …

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