Climate change will alter our landscape gradually, so the experts tell us, but economics and the energy crisis have a much more immediate effect. If you have had a drive around virtually any part of lowland England in the past few weeks (or, for that matter, any lowland part of the UK), you may be forced to the conclusion that nature has discarded her traditional cloak of spring green ? this year?s fashionable spring colour is yellow.

In my part of the country, oilseed rape fields stretch far and wide; as the crop comes to full flower, its intense yellow dominates the landscape and overpowers the more gentle greens of the grain crops it has often replaced.

Though it was considered a rather unusual agricultural crop in the 1970s, there has been a gradual increase since then. Production gained momentum over the past decade, however, with DEFRA estimating a further increase of 17 per cent in oilseed rape production this year compared with last.

The reasons for this growth are political and economic. Through the gradual withdrawl of European Union subsidies, farmers now have less incentive to cultivate grain crops and there is a rapidly growing demand for oilseed, both for human consumption and for industrial processes. Thus two types of oilseed rape are grown. The crop for human consumption is used to produce cooking oil, margarine and a wide variety of additives for other foodstuffs, and there is also now a burgeoning market in pure single-pressed rapeseed oil that compares favourably to the finest olive oils.

The ?industrial? crop produces less palatable oils that contain trace compounds and acids useful in a wide variety of chemical processes. By far the most important factor is the recent growth in the production of biodiesel fuel and recently, with the rapid increase in rape acreage on Britain?s lowland farmland, the UK has become a net exporter of the crop. There is considerable opposition to this from some quarters. To achieve optimum production, oilseed rape has to be intensively farmed; it needs the attention of various selective herbicides and pesticides, so cannot really be organically farmed. When in full flower, the crop?s intense pollen production is also claimed to cause asthma and other respiratory problems, and some of the earlier industrial strains were suspected of being poisonous to wildlife ? deer in particular. There is also the constant fear of the unwitting introduction of GM strains.

There is an upside to the spread of this yellow crop across our countryside, however. According to the RSPB, oilseed rape has been a factor in halting the decline of the linnet and is a good food source for many other seed-eaters, such as buntings and finches. Oilseed rape also holds a wider variety of invertebrates than comparable grain fields, encouraging more insect-eaters and providing a valuable protein source for fledgling birds. For the pigeon shooter, the increasing area under oilseed rape provides a ?double season?.

The autumn-sown crop becomes a magnet for pigeon during the late winter months, particularly if a series of frosts ? remember them? ? locks up the ground and their other food sources have been used up. This is when pigeon will descend on the oilseed rape fields in their hoards, stripping the greenery from the young plants. At times, the dull winter green of the crop can have an extensive blue-grey overlay, as many thousands of hungry woodies systematically destroy the crop, stripping the field bare.

The other season for pigeon shooting follows the harvest in high summer. After flowering, the plants set seeds in tiny bean-like pods, the crop is either cut early and left to dry or is left to dry out naturally before harvesting. In either case, the pods become brittle and when the plants are combine harvested there can be a substantial spillage. Scanning one of these harvested fields through binoculars will pick out an impressive variety of birds reaping the benefits of their ?gleaning rights?; partridges ? both redlegs and greys ? linnets, meadow pipits, yellowhammers, goldfinches and greenfinches will all take advantage of this accidental bounty. Above all, however, there will be woodpigeon.

The countryside changes and I am satisfied that our yellowing landscape brings with it a measure of benefit to our biodiversity and increases the opportunities for pigeon shooting. I?m just relieved that William Blake isn?t still around ? In England?s yellow and pleasant land just doesn?t sound right.