Palaeoenvironmental and geomorphic evidence indicates that aridification intensified after ~5000 BP, reducing flood intensity and altering riverine landscapes in Greater Indus regions—setting conditions that would later challenge both inundation- and rain-based farming.
Around 2200 BCE, a major episode of increased aridity (often termed the 4.2 ka event) begins across parts of Afro-Eurasia. This climatic shift is frequently discussed as an important environmental backdrop for later Indus-region hydroclimatic stress.
Archaeological and landscape syntheses identify a pronounced shift after roughly 3,900 years ago (~1900 BCE): settlement sizes and total settled area decline, many sites are abandoned, and settlement density shifts eastward—marking the transition away from Mature Harappan urbanism.
The broader Localization Era is conventionally dated to c. 1900–1300 BCE, during which the previously wide-ranging material uniformity and long-distance exchange networks weaken, and regional cultural traditions become more prominent.
In the Punjab region, the Cemetery H culture develops as a Late Harappan regional expression, commonly dated c. 1900–1300 BCE. It is often interpreted as showing continuity alongside change in ritual practice and material culture within post-urban communities.
In Sindh (Lower Indus), the Jhukar phase is dated to roughly 1900–1500 BCE, reflecting non-uniform, regionally distinctive post-urban trajectories after the decline of Mature Harappan city life.
Late Harappan contexts are associated with a weakening of coast-to-interior and interregional exchange connectivity compared with the Mature Harappan period, consistent with broader economic and political decentralization during deurbanization.
By the early second millennium BCE, many major Harappan urban centers had been substantially depopulated or abandoned, reflecting the culmination of a multi-century shift from dense urban settlement to smaller, more localized rural and town networks.
Evidence synthesized from settlement distributions indicates a marked eastward shift in site numbers and density during the Late Harappan period, consistent with populations reorganizing toward areas with comparatively more reliable rainfall and/or water access.
Research syntheses emphasize that the Ghaggar-Hakra system was monsoon-fed and that reduced monsoon rainfall contributed to its becoming more seasonal/ephemeral, a change frequently linked with settlement reorganization and partial abandonment of some river-adjacent landscapes.
Late Harappan regional sequences (e.g., in parts of Sindh) include more clearly non-urban archaeological signatures and, in some interpretations, greater emphasis on mobile or mixed agro-pastoral strategies—consistent with adaptation to changing economic and hydrological conditions.
Climate syntheses argue that changing seasonal rainfall regimes—particularly interactions between summer and winter precipitation—help explain the transition from urban centers to more dispersed rural settlement patterns, framing decline as social transformation rather than abrupt collapse.
By about 1300 BCE, the Late Harappan (Localization Era) cultural horizon is generally considered to have ended, with regional cultural developments continuing into Early Iron Age contexts in parts of South Asia.
Michael CarricoThe Decline of Indus Urbanism: Climate, Economy and Social Transformation (c. 2200–1300 BCE)