Skylarks May Starve if British Farmers Use Genetically Modified Crops
EAST ANGLIA, United Kingdom, September 4, 2000 (ENS) - Songbirds like the skylark, renowned for its vertical flight and liquid trilling song, feed on the seeds of plants considered weeds by farmers. These birds will suffer if genetically modified herbicide tolerant crops replace formerly weed abundant fields, a new British study has found.
Lead author Andrew Watkinson, from the University of East Anglia, in Norwich, England, and his colleagues have created a model that simulates the growth of weed populations within crops.
Using the model, the team investigated the consequences of the changed herbicide use associated with genetically modified herbicide tolerant crops.
Robert Freckleton, and William Sutherland, of the University of East Anglia, in Norwich, England, and Robert Robinson, of the British Trust for Ornithology, in Norfolk, England contributed to the research. Their study was funded by the University of East Anglia and the Natural Environment Research Council. The results are published in the current issue of the international journal, "Science."
Overall, the study found, the consequences to birds should depend upon which farmers adopt the new crop types. Weed seed populations can be expected to decline by at least 90 percent in some cases.
The study links the decline in weed numbers to bird numbers, predicting that such a decline in seed abundance may seriously reduce the numbers of skylarks using these fields.
The controversial field trials now underway in the United Kingdom are intended to investigate the consequences of genetically modified herbicide tolerant crops for biodiversity.
"The field trials will be very valuable, but will not tell us what will happen to bird populations. They are carried out on too small a scale. One considerable advantage of the methodology we have adopted is that it enables us to make predictions now rather than having to wait for the results of a three year trial," Watkinson said.
Several decades of intensified agriculture in Europe have had a particularly serious effect on birds, whose populations in the United Kingdom have declined by up to 90 percent in the last 25 years, Watkinson said.
"It seems likely that the widespread introduction of herbicide tolerant crops will result in further declines for many farmland birds unless other mitigating measures are taken," he said.
The model developed by Watkinson's team examines the management of herbicide resistant sugar beet and its effects on a major annual weed of that crop (Chenopodium album, more commonly known as Lamb's Quarters in North America and Fat Hen in Britain) and the seed eating skylark Alauda arvensis.
"These results probably apply widely to other crops, weeds, and seed eating birds," noted Watkinson.
The study showed that a key issue in predicting the impacts on bird numbers was the pattern of farmers' uptake of the new genetically modified technology. Most fields have very low seed densities. It is the fields with high seed densities that are particularly important for bird populations.
The researchers predict that the severity of the bird declines will depend upon which farmers are most likely to adopt the genetically modified herbicide tolerant crops. If their use is restricted to intensive farms with low seed densities then the effect will be minor.
But, if the herbicide hardy crops are adopted by a wide range of farmers - especially farmers with very weedy fields - then the bird declines are likely to be more severe, the study found.
A commentary by Les Firbank, of the Centre for Ecology and Hydrology, in Cumbria, England, and Frank Forcella at the U.S. Department of Agriculture's Agricultural Research Station in Morris, Minnesota, and the University of Minnesota, in St. Paul, Minnesota, accompanies the "Science" paper.
Firbank and Forcella write that the model provides a "welcome conceptual framework," but that further work will be necessary to resolve some of the model's simplifications.
Some data from the United States, where genetically modified herbicide tolerant crops are currently growing, suggest that weed control with genetically modified herbicide tolerant crops may not be as effective as some of the model results indicate.
Such differences emphasize the need for field trials to complement theoretical studies like this one, Firbank and Forcella point out.
One of the most widespread birds of the British Isles, with over two million breeding pairs, the resident population is joined in winter by a significant proportion of the northern European population - possibly up to 25 million individuals. Still, the UK breeding population of skylark on lowland farmland declined by 54 percent between 1969 and 1991. The population has also declined substantially in many other European countries.