Human activity has increased massively in the last century, including a quadrupling of human population and a 40-fold increase in economic activity. By 2050 we expect the population to increase to over 9 billion and incomes to rise. To 'make it fit' we need to sufficient economic growth to provide a decent standard of living to all people, and we need to maintain the ecosystem processes and environmental quality that support human well-being. Water quality is one environmental quality that has been heavily impacted through the last century and is intimately tied to the goals of sustainable development through the production of food, energy and consumable goods.
We have developed a relatively simple but spatially explicit and interconnected model to evaluate development scenarios for trade-offs in our attempts to 'make it fit' by providing a decent quality of life for all while maintaining environmental quality. In particular, the water quality sub-model tracks the stocks and flows of nitrogen, phosphorus and silica from terrestrial sources to aquatic accumulations.
We specifically track nitrogen deposition, nitrogen and phosphorus fertilizer inputs required to meet crop yield goals and pasture productivity, harvested nitrogen and phosphorus from crops and pastured animals, nitrogen and phosphorus pollution from inland aquaculture, biological nitrogen fixation in natural and cropland systems, and the flow of nitrogen and phosphorus through humans and waste water treatment plants, including the shifting distribution of waste water treatment capabilities. Nitrogen and phosphorus balances are retained to various degrees and routed downstream to coastal zones.
Results/Conclusions
Initial model runs for the present showed considerable errors in the phosphorus component. We have since improved our calculations of the phosphorus balance and phosphorus retention. By integrating with an agriculture model that spatially allocates land, nitrogen and phosphorus to produce calories we produced much more detailed comparisons of current agricultural nitrogen and phosphorus pollution versus future inputs, including the effects of reducing fertilizer waste.