The rise in abundance of algae in coastal waters is thought to be due to increases in nutrients such as nitrate and other forms of nitrogen. Researchers gathered data to gauge the evidence that nitrates in the discharges of rivers around the world are associated with human population density.
ex1221A data frame with 42 observations on the following 11 variables.
Rivera character vector indicating the river
Countrya factor variable with 26 levels
Dischargethe estimated annual average discharge of the river into an ocean (m\(^3\) per second)
Runoffestimated annual average runoff from the watershed (liters/(sec\(\times\) km\(^2\)))
Areawatershed area (km\(^2\))
Densitydensity of people (people/km\(^2\))
NO3nitrate concentration (\(\mu\)M/l)
Exportnitrate export (product of runoff times nitrate concentration)
Depdeposition (proportional to product of nitratrate precipitation times precipitation)
NPrecnitrate precipitation (\(\mu\)mol NO\(_3\)/(sec\(\times\)km\(^2\)))
Precprecipitation (cm/year)
Cole, J.L., Peierls, B.L., Caraco, N.F. and Pace, M.L. (1993). Nitrogen Loading of Rivers as a Human-driven Process, in McDonnell, M.J. and Pickett, S.T.A. (eds.) Humans as Components of Ecosystems: The Ecology of Subtle Human Effects and Populated Areas, Springer-Verlag.