Agricultural insecticides threaten surface waters at the global scale
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Edited by Jules M. Blais, University of Ottawa, Ottawa, Canada, and accepted by the Editorial Board March 13, 2015 (received for review January 6, 2015)http://www.pnas.org/content/early/2015/04/08/1500232112.abstract
Significance
Agricultural systems are drivers
of global environmental degradation. Insecticides, in particular, are
highly biologically
active substances that can threaten the
ecological integrity of aquatic and terrestrial ecosystems. Despite
widespread insecticide
application to croplands worldwide, no
comprehensive field data-based evaluation of their risk to global
surface waters exists.
Our data show, for the first time to our
knowledge at the global scale, that more than 50% of detected
insecticide concentrations
(n = 11,300) exceed regulatory
threshold levels. This finding indicates that surface water pollution
resulting from current
agricultural insecticide use constitutes
an excessive threat to aquatic biodiversity. Overall, our analysis
suggests that
fundamental revisions of current
regulatory procedures and pesticide application practices are needed to
reverse the global
environmental impacts of
agrochemical-based high-intensity agriculture.
Abstract
Compared with nutrient levels and
habitat degradation, the importance of agricultural pesticides in
surface water may have
been underestimated due to a lack of
comprehensive quantitative analysis. Increasing pesticide contamination
results in decreasing
regional aquatic biodiversity, i.e.,
macroinvertebrate family richness is reduced by ∼30% at pesticide
concentrations equaling
the legally accepted regulatory threshold
levels (RTLs). This study provides a comprehensive metaanalysis of 838
peer-reviewed
studies (>2,500 sites in 73 countries)
that evaluates, for the first time to our knowledge on a global scale,
the exposure
of surface waters to particularly toxic
agricultural insecticides. We tested whether measured insecticide
concentrations (MICs;
i.e., quantified insecticide
concentrations) exceed their RTLs and how risks depend on insecticide
development over time and
stringency of environmental regulation.
Our analysis reveals that MICs occur rarely (i.e., an estimated 97.4% of
analyses
conducted found no MICs) and there is a
complete lack of scientific monitoring data for ∼90% of global cropland.
Most importantly,
of the 11,300 MICs, 52.4% (5,915 cases;
68.5% of the sites) exceeded the RTL for either surface water (RTLSW) or sediments. Thus, the biological integrity of global water resources is at a substantial risk. RTLSW
exceedances depend on the catchment size, sampling regime, and sampling
date; are significantly higher for newer-generation
insecticides (i.e., pyrethroids); and are
high even in countries with stringent environmental regulations. These
results suggest
the need for worldwide improvements to
current pesticide regulations and agricultural pesticide application
practices and
for intensified research efforts on the
presence and effects of pesticides under real-world conditions.
Footnotes
- 1To whom correspondence should be addressed. Email: schulz{at}uni-landau.de.
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Author contributions: S.S. and R.S. designed research; S.S. and R.S. performed research; S.S. compiled the data; S.S. analyzed data; and S.S. and R.S. wrote the paper.
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The authors declare no conflict of interest.
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This article is a PNAS Direct Submission. J.M.B. is a guest editor invited by the Editorial Board.
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Data deposition: The data reported in this paper have been deposited at math.uni-landau.de/ecotox/publications/stehleandschulz2015.
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This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1500232112/-/DCSupplemental.
Freely available online through the PNAS open access option.
