What are the environmental impacts of excessive fertiliser use?

Excessive fertiliser use can lead to water pollution, soil degradation, and harm to wildlife.

When fertilisers are applied in large quantities, they can exceed the capacity of plants to absorb them. The excess nutrients, particularly nitrogen and phosphorus, can then be washed off the land by rainwater and enter rivers, lakes, and oceans. This process is known as nutrient runoff. The high nutrient levels in the water can cause a rapid growth of algae, a phenomenon known as algal bloom. When these algae die and decompose, they consume large amounts of oxygen, leading to areas of low oxygen, or 'dead zones', where most aquatic life cannot survive. This process is called eutrophication and it can devastate aquatic ecosystems.

Excessive fertiliser use can also degrade the quality of the soil. Fertilisers can increase the acidity of the soil, which can harm beneficial soil organisms and affect plant growth. Over time, this can lead to soil erosion and loss of soil fertility. In addition, some fertilisers contain heavy metals, such as cadmium and lead, which can build up in the soil and pose a risk to human health if they enter the food chain.

Furthermore, the production and use of synthetic fertilisers contribute to the emission of greenhouse gases, particularly nitrous oxide, which is a potent greenhouse gas. This can contribute to global warming and climate change.

Lastly, excessive fertiliser use can harm wildlife. For example, birds and mammals that rely on aquatic ecosystems can be affected by the loss of their food sources due to eutrophication. In addition, some fertilisers can be toxic to certain species, causing direct harm. For instance, the use of fertilisers containing pesticides can harm bees and other pollinators, which play a crucial role in our ecosystems and food production.