Pesticides are applied
in large quantities to agroecosystems worldwide.
To date, few studies assessed the occurrence of pesticides in organically
managed agricultural soils, and it is unresolved whether these pesticide
residues affect soil life. We screened 100 fields under organic and
conventional management with an analytical method containing 46 pesticides
(16 herbicides, 8 herbicide transformation products, 17 fungicides,
seven insecticides). Pesticides were found in all sites, including
40 organic fields. The number of pesticide residues was two times
and the concentration nine times higher in conventional compared to
organic fields. Pesticide number and concentrations significantly
decreased with the duration of organic management. Even after 20 years
of organic agriculture, up to 16 different pesticide residues were
present. Microbial biomass and specifically the abundance of arbuscular
mycorrhizal fungi, a widespread group of beneficial plant symbionts,
were significantly negatively linked to the amount of pesticide residues
in soil. This indicates that pesticide residues, in addition to abiotic
factors such as pH, are a key factor determining microbial soil life
in agroecosystems. This comprehensive study demonstrates that pesticides
are a hidden reality in agricultural soils, and our results suggest
that they have harmful effects on beneficial soil life.
Soil contamination is one of the main threats to ecosystem health and sustainability. Yet little is known about the extent to which soil contaminants differ between urban greenspaces and natural ecosystems. Here we show that urban greenspaces and adjacent natural areas (i.e., natural/semi-natural ecosystems) shared similar levels of multiple soil contaminants (metal(loid)s, pesticides, microplastics, and antibiotic resistance genes) across the globe. We reveal that human influence explained many forms of soil contamination worldwide. Socio-economic factors were integral to explaining the occurrence of soil contaminants worldwide. We further show that increased levels of multiple soil contaminants were linked with changes in microbial traits including genes associated with environmental stress resistance, nutrient cycling, and pathogenesis. Taken together, our work demonstrates that human-driven soil contamination in nearby natural areas mirrors that in urban greenspaces globally, and highlights that soil contaminants have the potential to cause dire consequences for ecosystem sustainability and human wellbeing.
The intensive use of pesticides and their subsequent
distribution
to the environment and non-target organisms is of increasing concern.
So far, little is known about the occurrence of pesticides in soils
of untreated areas—such as ecological refuges—as well
as the processes contributing to this unwanted pesticide contamination.
In this study, we analyzed the presence and abundance of 46 different
pesticides in soils from extensively managed grassland sites, as well
as organically and conventionally managed vegetable fields (60 fields
in total). Pesticides were found in all soils, including the extensive
grassland sites, demonstrating a widespread background contamination
of soils with pesticides. The results suggest that after conversion
from conventional to organic farming, the organic fields reach pesticide
levels as low as those of grassland sites not until 20 years later.
Furthermore, the different pesticide composition patterns in grassland
sites and organically managed fields facilitated differentiation between
long-term persistence of residues and diffuse contamination processes,
that is, short-scale redistribution (spray drift) and long-scale dispersion
(atmospheric deposition), to offsite contamination.
Increasing the number of environmental stressors could decrease ecosystem functioning in soils. Yet this relationship has not been globally assessed outside laboratory experiments. Here, using two independent global standardized field surveys, and a range of natural and human factors, we test the relationship between the number of environmental stressors exceeding different critical thresholds and the maintenance of multiple ecosystem services across biomes. Our analysis shows that having multiple stressors, from medium levels (>50%), negatively and significantly correlates with impacts on ecosystem services and that having multiple stressors crossing a high-level critical threshold (over 75% of maximum observed levels) reduces soil biodiversity and functioning globally. The number of environmental stressors exceeding the >75% threshold was consistently seen as an important predictor of multiple ecosystem services, therefore improving prediction of ecosystem functioning. Our findings highlight the need to reduce the dimensionality of the human footprint on ecosystems to conserve biodiversity and function.
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