Salinity fundamentally reshapes crop competitiveness and optimal land‑use portfolios in a high-value agricultural landscape

Salinity intrusion is an emerging threat in low‑lying regions as climate‑driven fluvial/tidal flooding intensifies. Yet its impacts remain poorly characterised due to focus on biophysical processes and limited understanding of how it affects agricultural productivity, profitability, and risk exposure. The study sought to quantify the impact of flood‑induced salinisation on crop productivity and profitability, assess how it alters risk-return relationships, and evaluate how this affects crop competitiveness and optimal land‑use portfolios. The study focused on Greater Lincolnshire, United Kingdom as a case, and used spatially explicit crop, land‑grade, and flood‑risk datasets integrated with enterprise‑level gross‑margin modelling, Monte‑Carlo simulation, and cross‑crop competitiveness analysis. Without flood-induced salinisation, profitability varies across crops, with margins from £ 1114/ha for beet and £ 825/ha for winter wheat to £ 255/ha for potatoes. Under the salinity scenario, all crops incur substantial losses from simulated yield declines. Potatoes show the greatest drop (–£1382/ha), followed by beet (–£442/ha) and cereals such as winter wheat (–£339/ha), spring wheat (–£273/ha), and spring barley (–£304/ha). Risk-return analysis reveals that salinity systematically collapses the profitability hierarchy across crops, compressing them into a uniformly low‑return, moderate‑risk zone and thereby eliminating the high‑value production opportunities that currently underpin regional agricultural competitiveness. Competitiveness shifts markedly, with potatoes most disadvantaged and barley relatively resilient, while portfolio optimisation indicates strong reallocation toward winter wheat. Overall, the scenario suggests that flood‑induced salinisation could become a transformative constraint without flood defences, underscoring the need for proactive mitigation policies, adaptive planning, and investment in salt‑tolerant crop options.