Sustainable adaptation to climate change needs to be assessed beyond the present time and location to include the way that current forms of adaptation might influence future response options. An analysis of past dynamics of adaptation, what we call “trajectories,” might hold the key to understanding how the adaptive outcomes of past responses to climate stress constrain or open avenues to future adaptation. Adaptation research often focuses on particular actions, technologies, or institutions which may positively influence these relationships in order to build resilience and reduce vulnerability. However, relationships are complex and often behave in unexpected ways. There is no simple cause and effect, but rather actions are modified and transmitted through a web of linkages and feedbacks that are both physical and social. This complexity challenges our ability to predict the outcome of particular actions and there remain gaps in the understanding of system interactions that would permit a more accurate assessment of future development trajectories. The work presented here is an analysis of change in the climate vulnerability of dryland farmers in Northeast Brazil over four decades. The analytical framework, which links biophysical characteristics with a socio-economic context and indicators, permits an analysis that captures the dynamic relationship of adaptive capacities and consequent changes in vulnerability. The analysis of trajectories provides a foundation for future assumptions about human behavior and the relationship with the environment.