Across species, leaf lifespan (LL) tends to be correlated with leaf mass per area (LMA). Previously we found that Australian perennial species from low-rainfall sites had c. 40% shorter LL at a given LMA than high-rainfall species. Here we relate indices of leaf strength (work to shear, Wshear, and tissue toughness) to LL and LMA across the same suite of species. Wshearis the work required to cut a leaf with a blade; Wshear divided by leaf thickness gives tissue toughness. Low- and high-rainfall species did not differ in their LL at a given Wshear, but dry-site species had lower Wshear at a given LMA, leading to the observed LL- LMA shift with rainfall. These patterns were driven by 50% lower tissue toughness in dry-site species. The lower toughness was linked with high leaf N concentration, which is known to enhance water conservation during photosynthesis in low-rainfall species. Our results suggest that a significant cost of this strategy is reduced LL for a given investment in leaf tissue (LMA).