In the context of growing societal demands for land-based products, pressure on forest and agricultural areas is increasing. This dissertation explains some of the complexities of agricultural and forest dynamics, namely, the indirect consequences of agricultural intensification and the interconnection with agricultural expansion, and the non-linear trajectories and feedbacks of agricultural and forest areas' trajectories. The following three research questions were explored: i) What are the causal relationships between changes in cropland intensity and expansion and contraction of cropland areas? ii) What are the causal relationships and indirect effects between changes in forest, agricultural areas and major socioeconomic drivers? iii) Which factors and conditions shape an agricultural frontier’s trajectory? Combining panel data econometric techniques, causality analysis, theoretical modelling and qualitative data from experts’ interviews, this dissertation shows the importance of distinguishing between short and long run dynamics. In addition, the results provide evidence of a rebound effect in low and middle-income countries over the short run for several commodities with high price elasticity of demand, as well as a land sparing over the long run for some stable cereals. Furthermore, this dissertation made advances on old-fashioned ways of testing the Environmental Kuznets Curve (EKC), and the results show a rejection of the EKC for most of the country groups and globally, with the exception of high-income countries in the long run and post-forest transition countries in the short run. Lastly, the forest scarcity and the state of forest policy were the most relevant forest transition pathways. When zooming in on the agricultural frontier regions, this dissertation shows the important role of both structural and human agency factors -namely, the agglomeration economies and the actors’ expectations- on the frontier trajectory while also providing a framework to compare agricultural frontier areas according to their dependence on initial conditions or on both initial conditions and actors’ expectations.