Plant tolerance to herbivory affect plant growth and also tolerance are water, light, carbon dioxide and soil nutrients. Water and light levels are generally assumed to be positively associated with tolerance (Strauss and Agrawal 1999). However, there are exceptions such as evidence of decreased tolerance in "Madia sativa" with increased water availability (Wise and Abrahamson 2007, Gonzales "et al." 2008). Many studies have found CO levels to decrease tolerance in plants (Lau and Tiffin 2009). Increased nutrient levels are also commonly found to be negatively associated with tolerance (Wise and Abrahamson 2007). There are currently three prominent models that predict how resource levels may
Cultural eutrophication Cultural 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 as phosphates and nitrate are supplied to lakes and rivers, and then to coastal estuaries and bays. Extra nutrients are also supplied by treatment plants, golf courses, and agricultural practices through the use of fertilizers. Human activities, including the ones previously listed, can be responsible for an increase in nutrients, therefore, cultural eutrophication is more pronounced in non-polar ecosystems which have higher levels of human