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 Valuable for so much more than flight and song, birds hold a key
place in ecosystems worldwide. When bird numbers and varieties
dwindle, pest populations increase and much-needed pollination
decreases. Those examples alone negatively impact food
production and human health.
Likely reasons for the far-reaching and devastating declines
include intensified agricultural production, use of pesticides,
conversion of grassland to agricultural land, and climate
change. A new study from University of Illinois points to
increased use of neonicotinoid insecticides as a major factor in
the decline, says Madhu Khanna, distinguished professor in
agricultural and consumer economics at U of I and co-author on
the paper, published in Nature Sustainability.
Khanna says numerous studies have shown neonicotinoids –
nicotine-based pesticides – negatively affect wild bees, honey
bees, and butterflies, but large-scale studies on the
pesticide’s impact on birds have been limited. She speaks more
about the topic in a podcast from the Center for the Economics
of Sustainability at Illinois.
“This represents the first study at a national scale, over a
seven-year time period, using data from hundreds of bird species
in four different categories – grassland birds, non-grassland
birds, insectivores, and non-insectivores,” she says.
“We found robust evidence of the negative impact of
neonicotinoids, in particular on grassland birds, and to some
extent on insectivore birds after controlling for the effects of
changes in land use.”
Khanna and co-authors Yijia Li, a graduate student at U of I,
and Ruiqing Miao, assistant professor at Auburn University,
analyzed bird populations from 2008 to 2014 in relation to
changes in pesticide use and agricultural crop acreage.
The authors found that an increase of 100 kilograms in
neonicotinoid usage per county–a 12% increase on
average–contributed to a 2.2% decline in populations of
grassland birds and 1.6% in insectivorous birds. By comparison,
the use of 100 kilograms of non-neonicotinoid pesticides was
associated with a 0.05% decrease in grassland birds and a 0.03%
decline in non-grassland birds, insectivorous birds, and
non-insectivorous birds.
Since impacts accumulate, the authors estimate that, for
example, 100 kilograms neonicotinoid use per county in 2008
reduced cumulative grassland-bird populations by 9.7% by 2014.
These findings suggest that neonicotinoid use has a relatively
large effect on population declines of important birds and that
these impacts grow over time.
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According to the study, the adverse impacts on bird
populations were concentrated in the Midwest, Southern California,
and Northern Great Plains.
The researchers say the effect of neonicotinoids
could result directly from birds consuming treated crop seeds, and
indirectly by affecting the insect populations they feed on.
Consumption of just a few seeds is enough to cause long-term damage
to the birds’ reproduction and development.
The study included data on bird population and species diversity
from the North American breeding bird survey, a comprehensive
database with data from about 3,000 bird routes across the United
States. The researchers correlated the bird data with pesticide use,
as well as satellite data on agricultural crop acreage and urban
land use.
They examined whether intensified agricultural production and
conversion of grassland to agricultural land also contributed to the
bird decline. Results showed a small negative effect on grassland
birds related to cropland expansion, but no significant effect on
other types of birds.
While the use of other pesticides has been flat or declining,
neonicotinoid usage has grown exponentially over the past two
decades. Neonicotinoids are considerably more toxic to insects and
persist longer in the environment, the researchers note.
“This research provides compelling support for the re-evaluation of
policies permitting the use of neonicotinoids by the U.S.
Environmental Protection Agency by incorporating considerations of
the implications of these pesticides for bird habitats,” the authors
conclude.
The paper, “Neonicotinoids and decline in bird biodiversity in the
United States,” is published in Nature Sustainability [DOI:
10.1038/s41893-020-0582-x].
Authors include Yijia Li and Madhu Khanna, Department of
Agricultural and Consumer Economics, College of Agricultural,
Consumer and Environmental Sciences, University of Illinois; and
Ruiqing Miao, Department of Agricultural Economics and Rural
Sociology, Auburn University.
The project was supported by Hatch funding from the U.S. Department
of Agriculture (USDA), National Institute of Food and Agriculture (NIFA).
[Source: Madhu Khanna
News writer: Marianne Stein] |
