The global cycle of nitrogen has been altered by human activity to a greater extent than that of any other element. The production of nitrogen fertilizer, cultivation of legumes, and incidental nitrogen fixation in internal combustion engines together transfer more nitrogen from the atmosphere into biologically available forms than is fixed by all natural processes combined. Additionally, biomass burning and land-use change mobilize large quantities of recalcitrant nitrogen into dynamic forms. Although the global change in nitrogen cycling is immense, reactive and biologically available forms of nitrogen do not truly cycle globally. Rather, their transport is over distances of tens to many hundreds of kilometers. Consequently, the alteration of the global nitrogen cycle is manifested as changes at the scale of large regions. Since 1994 the International SCOPE Nitrogen Project has held a series of workshops focused upon nitrogen dynamics in several different regions of the globe.