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Overfertilisation happens when nature receives more nutrition than “natural”. This is most common in relation to emissions from agriculture, traffic and industry. Agriculture in particular is responsible for the overfertilisation of the Baltic Sea. Another word for this is eutrophication, which relates to particularly water.

Overfertilisation explained

Overfertilisation is when the soil or water gets too much nutrition, most common of nitrogen and phosphorus. These nutritions exist naturally in the soil. They are 2 of the most important nutrients that make plants grow.

The release of plant nutrients from the soil occurs naturally. Soil surface (that has not been damaged by humans) fixes large amounts of nitrogen and phosphorus. For example, the topsoil in a Swedish arable land contains about 2000 kg of phosphorus per hectare. In Scandinavia, where it rains and snows a lot, much of this nutrition enters the watercourses. As a result, soil nutrients end up in the oceans. However, humans interfere in this natural process by adding too much nutrition to the ground. This increase harms nature by causing overfertilisation.

Large bloom of alges, can be caused of overfertilisation.

Overfertilisation through agriculture

Today, agriculture is known for a large-scale and highly intensive practise. For example, it is very common to plough the Earth extensively. More so, to work with artificial fertilisation. Ploughing stirs up the soil, which increases the release of plant nutrients. This disturbs the natural balance. Furthermore, fertilisation adds too much plant nutrients to the ground. Which causes overfertilisation.

With the mechanised agriculture most common to recent decades, mineral fertilisers (chemical fertilisers) also arrived. This increased the intensity of cultivation and has caused much overfertilisation. However, there is a big difference on the outcome depending on what crop is being grown and how. More so, how the ground is being fertilised. These aspects have severe consequences. Therefore, our eating habits as consumers can have a direct impact on reducing overfertilisation. For example, there is a big difference between meat and crop production. Read more about this below.

The Baltic Sea & the Swedish coast

The Baltic Sea is an important and urgent example of the outcomes of overfertilisation. Just in 2014, the seas around Sweden (according to the Swedish Agency for Agriculture) received 114.600 tonnes of nitrogen and 3.340 tonnes of phosphorus from land and human activity. These emissions came largely from agriculture. Yet, also from sewage treatment plants, wastewater treatment plants and industries. These emissions sets off destructive chain reactions in the oceans.

The overfertilisation disturbs the balance between algae, plankton and various fish species. Some benefit extensively from the increased nutrition. While others are affected negatively. Hence, disturbing the natural balance. More so, the overfertilisation has created areas on the bottom of the sea that have no oxygen. In the worst cases, this causes the death of many seabeds. Furthermore, the increased nutrition leads to extensive algal blooms. Affecting all other life.

WWF estimates that the total amount of plant nutrients that reach the Baltic Sea (from all 9 neighbouring countries) contributes to an increase of nearly 1 million tonnes of nitrogen and around 30,000 tonnes of phosphorus per year. This has been recognised and attempts have been made to regulate the emissions. Which has made the state go back to the same level as in the 1950s. This development is positive, yet not close to sufficient. It is literally a question of life and death for the Sea. In order for it to survive, the emissions need to drop drastically. In fact, the Baltic Sea already has dead sea bottoms in a size on 1.5 times Denmark.

More solutions

Private people can do their part in working against overfertilisation. For example, eating more environmentally friendly has a positive effect. It is a fact that meat and dairy productions lead to higher emissions of plant nutrients. Meat and dairy products also contain high levels of nitrogen and phosphorus. These substances ultimately end up in treatment plants through our consumption. The emissions are not treated, instead, they eventually lead to overfertilisation. However, all kinds of farming plays a role in this problem. Fortunately, there are methods and initiatives that work against overfertilisation in the waters. Such as marine permaculture.

Sources: SVT, Jordbruksverket, WWF, Jordbruksverket (2)


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