Across the globe farmland and grassland birds are on the decline. As farmland needs to produce more crops it is more intensely managed. As crop production continues to climb the number of farmland birds continue to fall. But what is behind the decline.
A study published in PlosOne seems to show the biggest impact on reducing birds numbers – in the United States at least – is the use of pesticides rather than the intensification of crop production.
Using bird breeding surveys conducted between 1980 and 2003 the researchers found that the following were best predictors in bird decline ( in decreasing order):
- ‘lethal pesticide risk’
- insecticide use
- loss of cropped pasture,
The study indicated that direct pesticide toxicity was 3.9 times more plausible as a predictor of grassland bird losses than loss of cropped pasture demonstrating the impact that use of pesticides can have on birds.
The study found that loss of permanent pasture, proportion of land under cultivation and use of herbicides all had a limited impact on bird numbers.
The study points out the differences between pesticide use in the United States and Europe. The US have access to much more powerful pesticides which are toxic to birds while powerful pesticides are banned throughout Europe and so pesticide use may not have the same impact in Europe.
One of the interesting results of the study appears to be that increasing the amount of permanent pasture did not increase the amount of bird populations however an increase in cropped pasture did lead to a rise in farmland bird populations.
The study points out. “Our results suggest that the use of lethally toxic insecticides cannot be ignored when trying to identify causes of grassland population declines in North America. Indeed, they offer a more plausible explanation for overall declines than does the oft-cited ‘habitat loss through agricultural intensification’.
It was remarkable that loss of permanent pasture did not appear to be much of a predictor of grassland bird declines.”
The authors, Pierre Mineau and Mélanie Whiteside from Carleton University in Canada pointed out that it would be foolhardy to ignore loss of habitat as being important to the decline in farmland birds but that use of powerful insecticides should be viewed as an important contributing factor in the loss of grassland birds.