This paper introduces a general framework for analyzing the impacts of regional and global technological change on long run agricultural output, prices, land rents, land use, and associated GHG emissions. In so doing, it facilitates a reconciliation of the apparently conflicting views of the impacts of agricultural productivity growth on global GHG emissions and environmental quality. As has been previously recognized, in the case of a global change in farm productivity, the critical condition for an innovation to lead to diminished land use is that the farm level demand for agricultural products is inelastic. However, in the more common case where the innovation is regional in nature, the necessary condition for a reduction in global land use and associated GHG emissions is more complex and depends on the relative yields, emissions efficiencies and supply conditions in the affected and unaffected regions. While innovations in agricultural are most common land-sparing at global scale, innovations in regions commanding a small share of global production, with relatively low yields, high land supply elasticities and low emissions efficiencies can lead to an increase in global land use change emissions. A numerical example illustrates these points and suggests that these conditions may hold for productivity shocks in Latin America and Sub-Saharan Africa. These insights are also relevant for the emerging literature on the effect of adverse climate change on global agriculture and associated emissions from land use change.