Sites with dead zones (oxygen depletion on the sea bottom)
Dead zones (hypoxic i.e. oxygen deficient water) in the coastal zones are increasing, typically surrounding major industrial and agricultural centers. This is commonly occuring due to nutrient pollution, in the form of nitrogen and phosphorous leading to algal blooms and eutrophication
01 Feb 2008 - by Hugo Ahlenius, UNEP/GRID-Arendal
Discharge of selected pollutants
Nitrogen and phosphorous represents nutrients that can be seen as pollutants, as large concentations of those increase eutrophication. Nutrients are present in primarily commercial fertilisers and in sewage. A measure of eutrophication is biochemical oxygen demand (BOD), which measures the activity in the water column. High BOD means that there is low water quality (in terms of eutrophication) and high activity of bacteria in the water. This grap...
29 Nov 2007 - by Philippe Rekacewicz, UNEP/GRID-Arendal
Reactive nitrogen on earth by human activity, with projection to 2050
The range of the natural rate of bacterial nitrogen fixation in natural terrestrial ecosystems (excluding fixation in agroecosystems) is shown for comparison. Human activity now produces approximately as much reactive nitrogen as natural processes do on the continents.
30 Nov 2007 - by Philippe Rekacewicz, Emmanuelle Bournay, UNEP/GRID-Arendal
Reforestation, town of Galma and surroundings, Niger 1975 and 2003
In 1970s and 1980s - years of environmental crisis, there were few trees remaining in Niger. Wind-blown sands razed farmers' young crops and they often had to plant crops three times to succeed. Since the middle of the 1980s in the most densely populated parts of Niger farmers have begun to protect and manage young trees and bushes regenerating on their cultivated fields. This is natural farmer-managed forest regeneration. Some trees fix nitrogen...
01 Oct 2008 - by Hugo Ahlenius, UNEP/GRID-Arendal
Nitrate levels: concentrations at river mouths
Nutrients are essential to life. In aquatic systems, nitrogen and phosphorus are the two nutrients that most commonly control the growth of aquatic plants, algae and bacteria. Nitrogen and phosphorus are considered to be the primary drivers of eutrophication of aquatic ecosystems, where increased nutrient concentrations lead to increased primary productivity. Some systems are naturally eutrophic, whereas others have become eutrophic as a result o...
26 Jan 2009 - by Philippe Rekacewicz
Industrial areas and seasonal zones of oxygen depleted waters
This graphic illustrates the strong link between areas with high densities of industrial activity and zones of seasonally oxygen-depleted waters.
There is a strong link between areas with high densities of industrial activity and zones of seasonal oxygen-depleted waters. In recent years there has been an increasing focus on treating and reducing municipal and industrial waste, and on reducing nitrogen levels in agricultural runoff. However, less...
26 Jan 2009 - by Phillipe Rekacewicz, (Le Monde diplomatique) February 2008