Modern agriculture and pesticides
The increase in intensive agricultural practices, which has developed progressively, especially from the early 1950s onwards has generated agricultural systems increasingly distant from an ecological balance.
In these conditions, and especially in the presence of high specializations and low biodiversity of crops, the production system has become increasingly fragile and susceptible to attacks by pathogens. In fact, we know that, as a rule, harmful organisms spread less rapidly in intercrops, due to the different susceptibility to insects, pathogens and due to the greater abundance and efficiency of natural enemies (Altieri M.A. et al. 2015).
Among other things, the use of species, varieties and breeds coming from other areas or from selections has often resulted in the lower resilience of these crops or livestock to different biotic or abiotic factors.
In these conditions, modern agricultural systems have had to resort to an ever-increasing use of synthetic substances.
In these conditions, however, numerous and progressive negative effects on the agricultural and natural environment appear. One of these is certainly, as mentioned, the loss of biodiversity, pollution and the consequent fragility of ecosystems.
These substances, often synthetic, kill insects, fungi and plants and, with their residues and metabolites, accumulate in the food chain, worsening the healthiness of foods, negatively impacting the survival of numerous species of birds, amphibians, reptiles, mammals and fish that feed on contaminated organisms. Furthermore, the disappearance or decrease of certain species means the loss of a step of some food chains and the interruption of ecological relationships which negatively affect the next step.
One of these phenomena is that of the decrease in insects, also renamed by researchers as the “windshield effect”, that is, that phenomenon that is noticed when traveling by car and finding oneself with a windshield full of insects.
The windshield effect, and the gradual observation that this phenomenon has become increasingly evident over the years, has been confirmed by some scientific studies.
According to some meta analyses, the extermination of insects is progressing at a worrying rate which, according to some studies published in Biological Conservation, puts it at 2.5 percent; however this is an absolutely approximate number. 40 percent of known insect species are in constant decline; a third of the species are critically endangered. And it is no coincidence that in the UN 2030 Agenda for Sustainable Development, the objective “Protect, restore and promote sustainable use of the earth’s ecosystem” appears as goal number 15.
In 2014, the journal Science attempted to quantify this decrease by calculating a summary of the results of several scientific studies already concluded: the result, for some monitored species, was a drop of 45 percent. More specific and limited research has produced even more alarming numbers. For example, the quantity of flying insects in German nature reserves has reduced by 75 percent over the last quarter of a century. Over the past twenty years, the monarch butterfly population in the United States has declined by 90 percent, with a loss of approximately 900 million individuals. In England, 58 percent of the butterflies present in cultivated fields have disappeared in less than ten years (period 2000 – 2009).
So far, around one million species of insects have been cataloged and described. But entomologists think that there are another four million “submerged” species, that is, not yet determined by man and, therefore, completely ignored by science. Such impressive numbers, tangible proof of nature’s biodiversity, are associated with the risk that, in the case of insects, serious problems for everyone will arise not with the disappearance of a species, but also just with that decrease that experts call “functional extinction”, that is, when the decline of an insect species is such that it is sufficient to put its function within an ecosystem at risk.
There are several birds and fish that feed on insects, and if these become too few, food and general feeding problems arise. Similarly, in the case of insects, a loss of even just 30 percent of the quantity of a species can be so destabilizing as to cause the total extinction of other species. And in 80 percent of cases it is precisely those who have suffered this secondary effect that disappear first.
Among the causes of this strong decrease in the insect population, according to research carried out, there are three in particular:
– the first concerns the destruction of natural habitats. In urban areas with the reduction of green and free spaces, in the countryside due to agricultural expansion which alters the balance of vegetation;
– secondly, insects are threatened by herbicides and insecticides: very powerful in their action, capable of introducing deadly poisons which then persist for long periods;
– finally, the most current cause, and also the one that is growing with greatest intensity: global warming. Even insects, at each latitude of the planet, are used to living and reproducing at certain temperatures. If these temperatures rise too much they are no longer able to lay their eggs and complete their cycles, and with this reproduction slows down. And this is what is happening.
Let us remember that insects perform fundamental ecosystem functions: in fact they are indispensable pollinators and recyclers of ecosystems. They are at the base of the food chain. Trillions of insects, moving from flower to flower, pollinate approximately three-quarters of the crops we eat, an activity worth 500 billion dollars a year. By eating and being eaten by birds and fish, insects transform plants into proteins and promote the growth of all the countless species that feed on them. There is also a completely invisible role for insects, but no less essential: decomposition, which allows the recycling of nutrients, keeps the soil healthy, promotes the growth of plants and the efficient functioning of ecosystems.
Unfortunately the scenario is even broader.
In fact, the synthetic products released into the ecosystem have also affected insects that performed particularly useful tasks for human environments; for example the disappearance of those who fed on mosquito larvae which had a negative impact on the spread of malaria, which reappeared in populations that the World Health Organization had now declared out of danger.
One of the most serious consequences is, as mentioned, on pollinating insects such as bees and other pollinators. The mortality rate of these insects is lately much higher than the natural mortality rate and among some of the most common causes is the use of insecticides.
To give an example, in Sichuan, a region in central-western China, farmers are forced to fertilize the flowers of their pear trees by hand, given that the uncontrolled use of insecticides and other poisons has exterminated the region’s bees. This in turn causes a loss of biodiversity because bees, traveling for kilometers, transport pollen far away, promoting hybridization between different plants.
Furthermore, the use of synthetic products has consequences on human populations.
Many research and dossiers have highlighted how large percentages of fruit and vegetables on our tables are contaminated with residues of one or more pesticides and a percentage of these products even have quantities of residues that exceed the limit allowed by current regulations.
Furthermore, pesticides are contaminating soil and water at an increasing rate: there are many examples of entire communities suffering from chronic poisoning from pesticides and other pollutants as the residues of some chemical compounds, even when used correctly, remain in the environment for years, resulting in a decrease in the quality of soil and groundwater resources, a phenomenon that has been known for decades and to which concrete and serious remedies have never been put in place (Galli L. et al. 1987).
Furthermore, the loss of biodiversity and production specializations have led to an increase in unwanted species, as they no longer have competitors or predators. This has led to the need for a further increase in the use of pesticides (particularly herbicides) which cause a further loss of biodiversity, triggering a vicious circle which, if not stopped quickly, will lead to very serious consequences, not only for the environment but also for all of humanity.
We also remember that the use of pesticides also has serious consequences on an economic level. First of all with the increase in the resistance of parasites, a factor that requires a further increase in their doses and then with the continuous search for new molecules which has repercussions on the increase in costs borne by farmers and, consequently, consumers. Indirect costs due to cases of acute intoxication, chronic pathological manifestations in humans and malformations due to the mutagenic effect of many synthetic products in intensive agricultural areas must also be considered in the account. In addition, obviously, to the costs caused by the reduced pollination of plants: let us remember that almost 10% of global agricultural production depends on this ecological service performed by bees and other insects.
Unfortunately, as the data (AA.VV. 2023) confirms, global agricultural consumption of pesticides has mostly grown steadily from 1990 to 2021. In the last year, pesticide consumption worldwide stood at almost 3 .54 million tons. This trend reflects the growing demand for crop protection chemicals.
In recent decades, to avoid or, in any case, reduce the use of synthetic molecules, the possible alternatives for farmers have essentially been biological control and integrated control. Biological control exploits the relationships of predation and competition already existing between living organisms, with the aim of containing the populations of harmful organisms, such as the use of ladybugs to fight aphids or other phytophagous plant insects, the use of crop rotation, the fight against harmful insects using the sterile male technique or the diffusion of sexual confusion pheromones, etc.
In addition to this, integrated pest control also involves the application of numerous measures, such as the use of more resistant crop varieties, allows the use of pesticides that are less harmful to humans and beneficial insects (selective products) and easily denatured by the environment. This approach is mainly used in the fight against insects, but can be extended to the fight against all harmful organisms (fungi, rodents, etc.). Its objective is to keep the harmful organism within a threshold in which it does not create economic damage, without eradicating it.
This first approach to the problem and the adoption of this type of agriculture has improved, for example, as already mentioned, the cultivation of rice throughout Asia. Harvests increased and where these techniques were adopted the use of pesticides decreased. In Indonesia, the natural fight against insect pests has replaced the use of insecticides by an equivalent of more than 100 million dollars a year while the rice harvest has increased by about 20 percent. Over the last 30 years, more than 50 countries have included forms of natural pest control in their national agricultural policies.
It is clear that the path taken is the right one but, at this point, it is clear that to completely escape from this system of absolute dependence on external factors and control procedures, which are sometimes very expensive, both for ecology and for economy, we need to change the production paradigm by moving towards an innovative model where the techniques are synchronized with the principles of nature, also using its services.
We can affirm that this transition represents the true and great green revolution, the only one that can guarantee the planet and therefore also humanity an integral ecological model which goes, precisely, under the name of agroecology.
This article is one of the summaries emerging from the forthcoming book on agroecology (spring 2024) signed by the undersigned and the other researchers: Giovanni Dara Guccione (CREA-PB), Barbara Manachini (UNIPA), Paola Quatrini (UNIPA) and with the preface by Luca Mercalli (president of the Italian Meteorological Society).