Eutrophication phosphate into water is slow, hence the difficulty of reversing the effects of eutrophication. However, numerous literature report that nitrogen is the primary limiting nutrient for the accumulation of algal biomass. The sources of these excess phosphates are phosphates in detergent, industrial/domestic run-offs, and fertilizers. With the phasing out of phosphate-containing detergents in the 1970s, industrial/domestic run-off and agriculture have emerged as the dominant contributors to eutrophication. Cultural eutrophication is the process that speeds up natural eutrophication because of human activity. Due to clearing of land and building of towns and cities, land runoff is accelerated and more nutrients such
The Limits to Growth continue indefinitely, but that a natural end to growth was preferable to intervention. Wallich stated that technology could solve all the problems the report was concerned about, but only if growth continued apace. By stopping growth too soon, Wallich warned, the world would be "consigning billions to permanent poverty". Julian Simon, a professor at the Universities of Illinois and, later, Maryland, argued that the fundamental underlying concepts of the "LTG" scenarios were faulty, because the very idea of what constitutes a "resource" varies over time. For instance, wood was the primary shipbuilding resource until the 1800s, and there were concerns