Insecticides can be beneficial to humans in many ways, such as providing crop protection from disease and defoliation and as a tool used in the reduction of mosquitoes and other insects that can transmit diseases such as malaria, to humans. However, once they enter an aquatic system, the environmental costs can be very high. Just how much of a threat these chemicals pose to aquatic biodiversity has been the focus of a recent study, highlighting regions most at risk.
The modelling study, published last month in the journal Environmental Pollution, has found that aquatic life present in water bodies within 40% of the global land surface is at risk from the runoff of insecticides from land. It is anticipated that the map, which shows the location of potential insecticide contamination, could assist freshwater management and conservation efforts by focussing on areas where mitigation measures should be concentrated.
In a recent article by SciDev, study researcher Matthias Liess, describes how tropical and subtropical areas may need to take urgent action to alleviate the risks to biodiversity from insecticide use. The research also notes that farmers in a number of developing countries are changing from subsistence farming to intensive crop farming.
“It is very helpful for environmental risk assessment and environmental management to have the information on insecticide occurrence on the landmass of countries. We can then identify where to find exposure hotspots, and where it is most relevant to plan mitigation measures.”
The study used maps and databases including data from the UN Food and Agriculture Organisation on country use of insecticides to produce a global insecticide runoff map that shows the vulnerability of runoff or the likelihood that rainwater will run off land into water bodies, based on the slope of the terrain and quantity of rainfall, as well as the runoff hazard related to the amount of insecticide used. This information is then combined to produce a global insecticide runoff map that shows how much insecticide is likely to contaminate water bodies.
The researchers found that in the northern hemisphere, insecticide runoff followed a latitudinal gradient which was predominantly driven by the insecticide application rate. However, in the southern hemisphere, a combination of daily rainfall intensity and insecticide application rate were the main contributing factors.
SciDev also quoted Luiz Cláudio Meirelles, a researcher at the National School of Public Health at the Oswaldo Cruz Foundation, as saying “there is a huge lack of information on everything related to agriculture and insecticide usage. The FAO has warned that some developing countries are using insecticides that are banned in developed countries.”
“But there’s a catch” he adds. “Countries such as Brazil have a larger biodiversity than other countries and this will always lead to more pests. Without proper data, resources and political will, we cannot provide more useful information and improve management efforts.”
According to Meirelles, when it comes to mitigation, political endorsement is essential because a higher level of insecticide use is often linked to valuable agricultural exports from countries such as Brazil.
CABI’s Environmental Impact database contains further information related to the impact of insecticides on aquatic biodiversity. A selection of these records is provided in the "further reading" section below.
Modeling global distribution of agricultural insecticides in surface waters. Ippolito, A., Kattwinkel, M., Rasmussen, J., Schäfer, R., Fornaroli, R., Liess, M. Environmental Pollution, 2015. 198, pp 54–60. doi:10.1016/j.envpol.2014.12.016
Macro-Invertebrate Decline in Surface Water Polluted with Imidacloprid. Van Dijk T., Van Staalduinen M., Van der Sluijs J. PLoS ONE, 2013. 8(5): e62374. doi:10.1371/journal.pone.0062374
Screening of native amphibians for deriving aquatic life criteria. Jin, C., ZhenGuang, Li, H., WeiLi, W., ZhengTao, L. Research of Environmental Sciences, 2014. 27(4) pp. 349-355.
Changes in pesticide occurrence in suburban surface waters in Massachusetts, USA, 1999-2010. Wijnja, H. Doherty, J. J. Safie, S. A. Bulletin of Environmental Contamination and Toxicology, 2014. 93(2) pp. 228-232. doi: 10.1007/s00128-014-1251-4
Changes in cholesterol content of the freshwater fish, Labeo rohita due to the effect of an insecticide 'encounter' (herbal plant extract). Binukumari, S. Vasanthi, J. International Journal of Pharmaceutical Sciences and Research (IJPSR), 2014. 5(2) pp 397-399.
Impact of Lihocin on immuno haematological and antioxidant enzyme indices of carp fish.
Vineela, D., Reddy, S. J. International Journal of Pharmacy and Life Sciences (IJPLS), 2014. 5(5) pp. 3517-3525.
Impact of an insecticide 'encounter' (herbal plant extract) on carbohydrate content in the freshwater fish, Labeo rohita. Binukumari, S., Vasanthi, J. Research Journal of Pharmaceutical, Biological and Chemical Sciences, 2013. 4(4) pp. 739-742.
Toxicity of the insecticide fipronil and its degradates to benthic macroinvertebrates of urban streams.
Weston, D. P. Lydy, M. J. Environmental Science & Technology, 2014. 48(2) pp. 1290-1297. doi:
Predicted transport of pyrethroid insecticides from an urban landscape to surface water. Jorgenson, B.. Fleishman, E., Macneale, K. H., Schlenk, D., Scholz, N. L., Spromberg, J. A., Werner, I., Weston, D. P., Xiao, Q. F., Young, T. M., Zhang, M. H. Environmental Toxicology and Chemistry, 2013. 32(11) pp. 2469-2477.