Modern agriculture relies on a small number of highly productive crops and the continued expansion of agricultural land area has led to a significant loss of biodiversity. In this paper we consider the macroeconomic consequences of a continued expansion of modern agriculture from the perspective of agricultural productivity and food production: as the genetic material supporting agriculture declines, pests and pathogens become more likely to adapt to crops and proliferate, increasing crop losses due to biological hazards. To evaluate the macroeconomic consequences of a reduction in agricultural productivity associated with the expansion of agriculture, we employ a quantitative, structurally estimated model of the global economy in which economic growth, population and food demand, agricultural innovations, and the process of land conversion are jointly determined. We show that even a small impact of global biodiversity on agricultural productivity calls for both a halt in agricultural land conversion and increased agricultural R&D in order to maintain food production associated with population and income growth.