Nutrients

{{ComponentTemplate2 |Application=Roads from Rio+20 (2012) project; Shared Socioeconomic Pathways - SSP (2014) project; The Protein Puzzle (2011) project; |IMAGEComponent=Drivers; Agricultural economy; Land-use allocation; Agriculture and land use; Aquatic biodiversity; Emissions; Land cover and land use; Livestock systems; |KeyReference=Beusen, 2014; Beusen et al., 2015; Beusen et al., 2016; Morée et al., 2013; |Reference=Bouwman et al., 2013c; Galloway et al., 2004; Zhang et al., 2010; Diaz and Rosenberg, 2008; UNEP, 2002; Rabalais, 2002; Beusen et al., 2015; Beusen et al., 2016 |InputVar=Population - grid; GDP per capita - grid; Land cover, land use - grid; Animal stocks; Livestock rations; Manure spreading fraction; Nitrogen deposition - grid; Actual crop and grass production - grid; Production system mix; Fertiliser use efficiency; |OutputVar=NH3 emissions - grid; N and P discharge to surface water - grid; Soil N budget - grid; Soil P budget - grid; N and P in wastewater discharge - grid; |Description=Human activity has accelerated the Earth’s biogeochemical nitrogen (N) and phosphorus (P) cycles through increasing fertiliser use in agriculture (Bouwman et al., 2013c). Increased use of N and P fertilisers has raised food production to support the rapidly growing world population, and increasing per capita consumption particularly of meat and milk (Galloway et al., 2004).

The side effect is that significant proportions of the mobilised N are lost through ambient emissions of ammonia (NH₃), nitrous oxide (N₂O) and nitric oxide (NO). Ammonia contributes to eutrophication and acidification when deposited on land. Nitric oxide plays a role in tropospheric ozone chemistry, and nitrous oxide is a potent greenhouse gas. Moreover, large proportions of mobilised N and P in watersheds enter the groundwater through leaching, and are released to surface waters through groundwater transport and surface runoff. Subsequently, nutrients in streams and rivers are transported to coastal marine systems, reduced by retention but augmented by releases from point sources, such as sewerage systems and industrial facilities.

This has resulted in negative impacts on human health and the environment, such as groundwater pollution, loss of habitat and biodiversity, an increases in the frequency and severity of harmful algal blooms, eutrophication, hypoxia and fish kills (Diaz and Rosenberg, 2008; Zhang et al., 2010). The harmful effects of eutrophication have spread rapidly around the world, with large-scale implications for biodiversity, water quality, fisheries and recreation, in both industrialised and developing regions (UNEP, 2002). Input of nutrients in freshwater and coastal marine ecosystems, also disturbs the stoichiometric balance of N, P and Si (silicon) (Rabalais, 2002) affecting total plant production and the species composition in ecosystems.

To assess eutrophication as a consequence of increasing population, and economic and technological development, IMAGE 3.0 includes a nutrient model ([[[Beusen, 2014][]; [[[Beusen et al., 2015][]; [[[Beusen et al., 2016]]]), which comprises three sub-models:

1. Wastewater module calculating nutrient flows in wastewater discharges (Figure Flowchart, top);
2. Soil nutrient budget module describing all input and output of N and P in soil compartments (Figure Flowchart, middle);
3. Nutrient environmental fate describing the fate of soil nutrient surpluses and wastewater nutrients in the aquatic environment (Figure Flowchart, bottom).

|ComponentCode=N |FrameworkElementType=state component }}