Increases in Fertilizers Cause Decreases in Biodiversity

06 May

Fertilizers became popular in the 1960s. Today there is double the amount of nitrogen and phosphorous in the soil compared to 50 years ago. Fertilizers became popular because they increase crop yields and are generally in expensive. However, until recently very little research was conducted to determine what other affects the added nitrogen and phosphorous had on the surrounding environment.

One common observation is that in locations where more fertilizers are used biodiversity decreases. Biodiversity is a common indicator of the overall health of the ecosystem being examined. Yann Hautier and Andy Hector, scientists from the University of Zurich, Switzerland recently tried to determine what causes a decrease in biodiversity in ecosystems with increased levels of nitrogen and phosphorous. To accomplish this they built their own experimental plant community from scratch. The results from their work suggests that the fertilizers enable some plants to grow rapidly and then their leaves create shadow and prevent the other species from getting enough light to grow and therefore they died off.

Decreases in biodiversity have many implications. One is there is more erosion and run off. The run off contains high levels on nitrates that are released from the soil when high levels of nitrogen are added. When the runoff travels to large bodies of water (ie: lakes or ocean), the nitrate levels in the water dramatically increase. High levels of nitrates in the water leads to prolific growth of aquatic algae (plants) like on land. In bodies of water this causes two problems.  First, the algae use up most of a water body’s oxygen then they die and are decomposed, creating “dead zones” that cannot support life. In addition, the algae growth covers the surface of the water and prevents sunlight from penetrating the ocean’s surface. Without sunlight no organism under the algae are able to survive. As a result deadzones have very low levels of biodiversity.

More research like Hautier and Hector’s is needed so we can fully understand how we are impacting ecosystems close to farms and far away, because its easy to tell that the ramifications are great and we clearly do not understand them all yet.



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Posted by on May 6, 2009 in Sustainable Agriculture


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