Too Much of a Good Thing: Human Activities Overload Ecosystems With Nitrogen
ScienceDaily (Oct. 8, 2010) — Humans are overloading ecosystems with nitrogen through the burning of fossil fuels and an increase in nitrogen-producing industrial and agricultural activities, according to a new study. While nitrogen is an element that is essential to life, it is an environmental scourge at high levels.
At Lake Atitlan in Guatemala, excess nitrogen promotes algae growth, which leads to eutrophication. Over-nourished by excess nutrients including nitrogen, which drains from nearby farms, swirls of blue-free algae form. The eventual decay of the algae robs the water of oxygen, and thereby creates a dead zone where other plants and animals cannot survive. (Credit: NASA Earth Observatory image by Jesse Allen, based on data from the NASA/GSFC/METI/ERSDAC/JAROS, and U.S./Japan ASTER Science Team)
According to the study, excess nitrogen that is contributed by human activities pollutes fresh waters and coastal zones, and may contribute to climate change. Nevertheless, such ecological damage could be reduced by the adoption of time-honored sustainable practices.
Appearing in the October 8, 2010 edition of Science and conducted by an international team of researchers, the study was partially funded by the National Science Foundation.
The Nitrogen Cycle
The nitrogen cycle--which has existed for billions of years--transforms non-biologically useful forms of nitrogen found in the atmosphere into various biologically useful forms of nitrogen that are needed by living things to create proteins, DNA and RNA, and by plants to grow and photosynthesize. The transformation of biologically useful forms of nitrogen to useful forms of nitrogen is known as nitrogen fixation.
Mostly mediated by bacteria that live in legume plant roots and soils, nitrogen fixation and other components of the nitrogen cycle weave and wind through the atmosphere, plants, subsurface plant roots, and soils; the nitrogen cycle involves many natural feedback relationships between plants and microorganisms.
According to the Science paper, since pre-biotic times, the nitrogen cycle has gone through several major phases. The cycle was initially controlled by slow volcanic processes and lightning and then by anaerobic organisms as biological activity started. By about 2.5 billion years ago, as molecular oxygen appeared on Earth, a linked suite of microbial processes evolved to form the modern nitrogen cycle.
Human Impacts on the Nitrogen Cycle
But the start of the 20th century, human contributions to the nitrogen cycle began skyrocketing. "In fact, no phenomenon has probably impacted the nitrogen cycle more than human inputs of nitrogen into the cycle in the last 2.5 billion years," says Paul Falkowski of Rutgers University, a member of the research team.
...
Read more here/Leia mais aqui: Science Daily
+++++
Science 8 October 2010:
Vol. 330. no. 6001, pp. 192 - 196
DOI: 10.1126/science.1186120
REVIEW
The Evolution and Future of Earth’s Nitrogen CycleDonald E. Canfield,1,* Alexander N. Glazer,2 Paul G. Falkowski3
Atmospheric reactions and slow geological processes controlled Earth’s earliest nitrogen cycle, and by ~2.7 billion years ago, a linked suite of microbial processes evolved to form the modern nitrogen cycle with robust natural feedbacks and controls. Over the past century, however, the development of new agricultural practices to satisfy a growing global demand for food has drastically disrupted the nitrogen cycle. This has led to extensive eutrophication of fresh waters and coastal zones as well as increased inventories of the potent greenhouse gas nitrous oxide (N2O). Microbial processes will ultimately restore balance to the nitrogen cycle, but the damage done by humans to the nitrogen economy of the planet will persist for decades, possibly centuries, if active intervention and careful management strategies are not initiated.
1 Institute of Biology and Nordic Center for Earth Evolution, University of Southern Denmark, Campusvej 55, Odense M, Denmark.
2 Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA.
3 Institute of Marine and Coastal Studies and Department of Earth and Planetary Sciences, Rutgers University, New Brunswick, NJ 08901, USA.
* To whom correspondence should be addressed. E-mail: dec@biology.sdu.dk
+++++
NOTA IMPERTINENTE DESTE BLOGGER:
Os pesquisadores precisam esclarecer COMO que by ~2.7 billion years ago, a linked suite of microbial processes evolved to form the modern nitrogen cycle with robust natural feedbacks and controls.
