Overfertilization happens when nature receives more nutrition than what is “natural”. This abundance occurs due to emissions from agriculture, traffic and industry. Agriculture, in particular, is responsible for the overfertilization of the Baltic Sea. Another word for this is eutrophication, which relates to the process in water.

Overfertilization explained

Overfertilization is when the soil or water gets too much nutrition, most commonly nitrogen and phosphorus. These nutrients exist naturally in the ground. They are the two most essential nutrients that make plants grow. The release of plant nutrients from the soil occurs naturally as the soil surface fixes large amounts of nitrogen and phosphorus. For example, the topsoil in Swedish arable land contains about 2000 kg of phosphorus per hectare. In Scandinavia, where it rains and snows, nutrition moves from the ground to the watercourses. As a result, soil nutrients end up in the oceans. However, humans interfere with this natural process by adding too much nutrition to the ground. This increase harms nature by causing overfertilization.

Overfertilization through agriculture

Today, agriculture is known for a large-scale and highly intensive practice, for example, by ploughing the Earth extensively. More so by using artificial fertilization. Ploughing stirs up the soil, which increases the release of plant nutrients. The activity disturbs the natural balance. Furthermore, fertilization adds too many plant nutrients to the ground, which causes overfertilization.

Modern agriculture also uses mineral fertilizers (chemical fertilizers). These products increased the intensity of agriculture and have caused much overfertilization. However, there is a big difference in the outcome depending on what crop is being grown and how. More so, how the ground gets fertilized. These aspects have severe consequences. Therefore, our eating habits as consumers can have a direct impact on reducing overfertilization. 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 essential and urgent example of the outcomes of overfertilization. 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 mainly from agriculture. Yet, also from sewage treatment plants, wastewater treatment plants and industries. These emissions set off destructive chain reactions in the oceans.

Overfertilization disturbs the balance between algae, plankton and various fish species. Some benefit extensively from increased nutrition, while others are affected negatively. This influence upsets the natural balance. Overfertilization has also created areas on the bottom of the sea with no oxygen. In the worst cases, entire seabeds have died. Furthermore, 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 nine neighbouring countries) contributes to an increase of nearly one million tonnes of nitrogen and around 30,000 tonnes of phosphorus per year. These amounts are well-known, and governments have tried to regulate the emissions. So far, the regulations have reduced the level to the state of the 1950s. This development is positive, yet much more is needed. It is a question of life and death for the sea. For it to survive, the emissions need to drop drastically. The Baltic Sea already has dead sea bottoms bigger than the size of Denmark.

More solutions

Individuals can do their part in working against overfertilization. For example, eating in an environmentally friendly way has a positive effect. It is a fact that meat and dairy products 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. Yet, they do not get treated there. Instead, they eventually lead to overfertilization. However, all kinds of farming play a role in this problem. Fortunately, some methods and initiatives work against overfertilization in the waters. Such as marine permaculture.

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