Farm-scale evaluations

The UK’s farm-scale evaluations were major investigations into animal and plant life diversity across farms in England, Scotland and Wales. They were completed to address whether growing genetically modified (GM) crops would impact on UK wildlife, but the technique can be modified to look at many aspects of farming practices on a large, country-wide scale.

Therefore, it’s a technique which could be crucial for gauging agricultural production to meet food security needs – and answer questions about the impact of different arable techniques on biodiversity and the environment.

The GM farm-scale evaluations were the largest and most thorough studies of their kind in the world. The study involved 266 trial fields, lasted 5 years, cost £6M and was overseen by an independent Scientific Steering Committee.

The GM crops had been genetically modified to make them herbicide-tolerant (GMHT) so that broad-spectrum herbicides could be applied that would kill weeds but not the food crop. The GMHT maize, and spring rape were resistant to the broad-spectrum herbicide Liberty (glufosinate-ammonium). The GMHT beet was resistant to the broad-spectrum herbicide Roundup (glyphosate). Other GM crops, such as ones resistant to certain insect pests, were not included in the study.

Researchers found that there were differences in the abundance of wildlife between the GMHT crop fields and conventional crop fields.

There were more insects, such as butterflies and bees, in and around the conventional beet and spring rape than GMHT beet and spring rape because there were more weeds to provide food and cover. The weeds also produce seeds, and there were less weed seeds in the GM beet and spring rape crops than in their wild counterparts.

Weed seeds are important in the diets of some animals, particularly farmland birds such as skylark, corn bunting and grey partridge, the numbers of which have declined in recent years. Some beetles, such as Harpalus rufipes, also feed on weed seeds.

Some species were more common in the beet and spring rape GM fields, notably springtails and one ground beetle species. The GM herbicides were used later in the season when the weeds were larger when treated, which provided a feast for the weed-feeding springtails; the beetle then tucked into the springtails.

Growing GMHT maize was better for many groups of wildlife than conventional maize. Because a different system of herbicide use was employed around the GMHT maize, there were more weeds in and around the GMHT crops, which led to more butterflies and bees around at certain times of the year, and more weed seeds.

The results show that different GM crops have different affects on wildlife abundance and biodiversity. But the differences arise because GMHT crops give farmers new options for weed control – they use different herbicides and apply them differently – not because the crops themselves have been genetically modified.

These trials compared GM with conventional crops, but their usefulness extends beyond the GM technology debate.

Researchers now have a UK database on wildlife living in and around conventional arable fields and how different species interact with one another. This gives researchers a starting point or baseline to monitor future changes to farmland ecosystems.

In the past, changes in agricultural practices, such as moving from spring-sown to winter-sown crops, or cutting down hedgerows between fields, have had significant effects on farmland wildlife, many detrimental. But these changes were never regulated, and their effects were difficult to measure.

This database will help researchers to monitor any major future changes in agricultural practices in the UK.