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There are numerous ways in which the current agricultural system harms the environment. The first of these, like with what impacts human health, is a result of the chemicals that need to be used by farmers to produce the large numbers of crops that are needed. These substances can enter the wider environment due to how they are applied and by being washed off of the crops they are applied to.

 

The issues with pesticides, herbicides and insecticides that all impact humans also have negative effects on wildlife for the same reasons. The poisons enter the food chain at a low level by covering grass etc, enter into smaller consumers, those smaller consumers are then eaten. Biomagnification means that further up the food chain there are major issues such as… (not sure what to do here, needs modern examples). These poisons are not naturally occurring and therefore cannot be broken down. They can also affect larger areas by being washed through the soil and into ground water. As these substances are designed to kill anything that the farmer does not want on their field (i.e. one specific plant), the poisons will kill large portions of the ecosystems that they enter.

 

In the case of fertilisers, these cause issues when they enter into water bodies. The unnatural increase in vital nutrients such as nitrates, phosphates and potassium can result in eutrophication. This is when algae grows rapidly to cover ponds. This prevents sunlight from entering the water and all underwater plants die, damaging the food chain. Soon, everything in the pond dies and is consumed by bacteria, leaving the pond devoid of life. This can be seen in the basic diagram below.

 

The preferred method of monoculture farming, i.e. growing one type of crop in a field to maximise ease of harvesting and profit, creates a very fragile and unvaried ecosystem. There are examples of historic issues with monoculture, such as the corn blight of 1970 which ruined more than 15 percent of corn crops in North America as 70% of the crop being grown at the same high yield variety, making the corn more susceptible to harmful organisms. 

 

The presence of a monoculture also leaves the soil itself vulnerable. Since there is only one type of plant growing there, it means the same substances are taken from the soil each time and more fertilisers are needed to substitute. Additionally, due to the harvesting of all of the grown crops, there is nothing left to turn into mulch and restore nutrients to the soil and build it back up. This means that the soil is vulnerable to erosion from wind and rain.

 

There are various things that farmers can and do do to avoid the full negatives of monocultures. One example is crop rotation where the farmer changes which crop is grown in that field to alter what nutrients are consumed with each harvest. There is also the use of cover crops: not growing crops in the field to harvest but rather plants that specifically help the nutrient content of the soil recover and protect it from soil erosion. The field is then replanted with the monetary crop after a certain amount of time has elapsed. However, these methods have the draw back of leaving fields temporarily unproductive or not growing the most profitable crop. This can be something that farmers may not be able to afford to do.