Ecological illiteracy? Does this contribute to food insecurity in Africa?

Since their discovery, pesticides have heralded a new dawn in increasing food productivity with their efficacy and efficiency in reduction of the yield-reducing pests and diseases which had put limitations on yield potential and meeting the ever-increasing human food demand. The availability of more food with advances in storage and processing has enabled humankind to conquer all the spheres of life. The application of pesticides intensively was a normal practice, until the eye-opening book by Rachel Carson, “The Silent Spring”. For the first time, the ecological consequences of pesticides were laid bare. Following this article by Wyckhuys et al 2019, there seems to be a major missing link between the application of pesticides and what farmer's practices are doing in relation to the environment, I have summarized some information about pesticides and their consequences, hoping that it will act as a guide to increasing farmers’ literacy in ecology.

Impact sources

Apparently, their success in the elimination of crop pests and diseases has a darker side that has not been accepted and evaluated comprehensively which is now being acknowledged to have negative consequences on the environment and human life. The interaction between pesticide active ingredients, bioactive substances, and the carrier materials comprising the entire pesticide formulation has different effects and impacts on human health and the environment. Direct contact especially among the applicators and those handling the pesticides in storage have the highest accumulation of active and inert materials that poses a grave danger to their health. Other secondary affected categories are those associated with drift from the wind, residues in fruits and vegetables being consumed without observing pre-harvest interval requirements, and contaminated water next to the site of application. Other tertiary affected category arises from the effects of leaching through rainwater into the water bodies and volatilization into the atmosphere in the process of pesticide breakdown.

Reasons for concern

Pesticide categories are based on toxicity with the most potent pesticides being labeled as highly hazardous pesticides (HHPs) due to their inherent nature of harming human health and severe environmental hazards, while they have chronic toxicity and are highly acute. These impacts have been categorized according to their effects on human health and the environment with scientific studies indicating the short, medium, and long-term effects which require further scrutiny in relation to ecological health. Though pesticides are normally applied on farms through sprays, soil incorporation, seed dressing, and dusting, their leaking beyond the boundaries of application is a matter of concern. Breakdown of the active ingredients to completely harmless substances often takes decades while volatilizing into the air, admixing with soil, and leaching with rain water or irrigation transfers the impacts to far beyond the point of application. The impacts can be classified as immediate, acute, cumulative, and interfering depending on the aspects that are negatively influenced by their presence either in low or high doses. Humans are classified among mammals and pesticide testing is normally done based on mammalian toxicity impacts. The negative interfering impacts are spread among the amphibians, birds, fish, insects/ invertebrates, reptiles, plants, and fungi.

Pesticide Chemical Formulations

There are different pesticides designed for specific functions and the site of action is determined by the active ingredients which define how they work and the range of pests controlled. The term pesticides define the whole spectrum of agricultural chemicals, while insecticides mainly refer to the range used to control pests. Pesticides comprise the primarily known fungicides, herbicides, insecticides, and rodenticides and also the lesser-known secondary types in the form of attractants, disinfectants, plant defoliants, and plant growth regulators. The science behind the development of a pesticide is based on the mode of action of the pesticide defining its range and covers; algicides (killing algae), antifoulants (kill or repel organism attaching to under water surfaces), antimicrobials (targets bacteria and viruses), attractants (bait or trap lure), biopesticides (natural derivatives from animals, bacteria, minerals or plants), biocides (broadly target microorganisms), defoliants (used to facilitate harvest by causing leaves to drop from plants), desiccants (promote tissue drying), disinfectants / sanitizers (inactivate/ kill disease causing microorganisms), fungicides (targets fungi – blights, mildews, molds & rust), fumigants (action through vapor or gas destroying through oxygen depletion), herbicides (target weeds either broadly or specially designed), insect growth regulators (growth disruption targeting specific insect stages or processes), insecticides (killing targets are arthropods and insects), miticides/ acaricides (targets insects in the category of acarina/mites), microbial pesticides (microorganism category with ability to inhibit, kill, or outcompete target insects and intended microorganism), molluscicides (targets slugs and snails), nematicides (root targeted to control microscopic worm like organisms), Ovicides ( targets eggs of insects and mites), pheromones (targets mating behavior of specific insects), plant growth regulators (intended to alter normal growth such as flowering to fit certain patterns), repellents (act through repelling certain insects), rodenticides (used in control of rodents such as mice and rats)

 The action of a pesticide defines its inherent, immediate, and perceived danger based on its immediate, after effects and associated relationship with other living and non-living objects in its ecosystems and the compound effects of its entire ecosystem. Pesticides, therefore, are an important study subject because of their spectrum of negative effects and long-term impacts.

 Verified Impact Studies Relating To Pesticides.

Endocrine disruption: described as external substances with the ability to change the normal functions of the endocrine systems resulting in negative health impacts in otherwise healthy populations through disturbance of the natural mechanism and inducing abnormality. Abnormalities are associated with interfered metabolic processes and altered behavioral functioning. Some famous types include DDT and other chlorinated additives.

Neurotoxicity: defined as damage to the brain or part of the nervous system resulting from exposure to man-made toxic substances such as pesticides altering and disrupting the activity of the nervous system including killing nerves. Most of these impacts are irreversible and the reason for concern after exposure which may have immediate or delayed responses based on the different characteristics, duration, and dosage of exposure. Some of the symptoms include limb weakness or numbness, loss of memory, vision, compulsive obsessive behaviors, delusions, headache, cognitive and behavioral problems, and sexual dysfunction.

Carcinogenicity: Increasing cases of cancer should be a concern globally. Carcinogens are substances that trigger cancer formation or result in birth defects. Some pesticides have been attributed to causing birth defects, miscarriages, and kidney damage. Other impacts linked to pesticides include learning/ developmental disabilities in children especially associated with pesticides passed through breast milk.  

Other impacts

Other concerns related to pesticides have been in the areas of toxicity to bees and aquatic fauna, behavioral disturbances, reproductive system damage, kidney damage, and Micronutrient deficiency (caused by the chelating effect).  Many impacts are still under research with increasing facts attributed to intensive pesticide usage.

What’s the Way Forward?

These points of concern should be an important consideration when the advice given to farmers in relation to the use of synthetic pesticides in the crop production processes. The lost ecosystem benefits including the loss of interrelated linkages between species such as predatory pests whose role is reducing pest pressure should never be ignored. Another challenge coming after the intensive usage of pesticides is the development of super bugs and super weeds that are resistant to all the known molecules in existence thereby making farmers increase dosages that are still not effective.

The urgently required adoption will be the ecological approach to enjoy the ecosystem benefits including the safeguarding of the bees for pollination services and reducing the leaching of pesticides into the aquatic systems.