When discussions on resource sustainability and peak oil/energy arise, there are two individuals who's ideas are often at the center of the debate/s. (the 2 profiles are linked to the wikipedia articles for the individual)
Thomas Robert Malthus (1766-1834)
An English demographer and political economist. He expressed views on population growth and discussed the idea of geometric population growth.
Marion King Hubbert (1903-1989)
A geoscientist who worked at the Shell research lab in Texas. He made important contributions to geology and geophysics, most notably the Hubbert curve and Hubbert peak theory (or peak oil),
These two individuals are just two of the many people who have laid the ground work for understanding the dynamics of humanities resource use patterns. However, these are two names that you will probably hear fairly often the more you look into peak oil and sustainability. take a look at their wiki articles, the back ground may help you understand some of the arguments that are based on their work and will allow to recognize when their names are just being uses as an appeal to authority.