Since 1990 South-Pembrokeshire has seen rapid changes to its once homogenous landscape dominated by dairy farms. An analysis of this differentiation was made using a system-based French method: an ‘agrarian diagnosis’ in which the current situation is perceived as being the result of both the constraints and qualities of the geographic context in which agriculture is situated, and of a history that has shaped its production methods and social structure. 92 semi-structured farm interviews were carried out in a discrete South Pembrokeshire area, formed of 3 different landscape units with a wide diversity of farm types, and combined with literature, documentary and secondary data analysis. From 1990, the relatively similar dairy farms across Pembrokeshire differentiated under sustained income pressure, linked to an output/input price squeeze and a challenging environment for business expansion. Those farms who stayed in dairying used different strategies to expand, at different times. A ruthless selection process took place, as many farms were pushed out of milk into beef and sheep. This was the first step in a trend towards renting out the land and retiring from farming altogether. The reduced pressure on land use in some farms allowed Potato farming to re-emerge in the landscape, among specialized farms and in just one landscape type. Gradually, a complex, interdependent ecosystem of farms has developed, with businesses exchanging outputs and inputs. The detailed modelling of current farming systems using functional ‘archetypes’, examining economic performance and agricultural income, allows us to understand the economic structure of land use. From this we can forecast a likely second turning point in farm evolution arising from the new support policy and emerging post-Brexit and post-Covid economic environment.