Quick Answer
A single supercontinent would create huge continental interiors far from the moderating influence of the sea. Coastal regions could remain relatively mild while the interior became more seasonal, dry and extreme. Ocean circulation and the distribution of habitats would also change.
Earth has repeatedly assembled and broken apart supercontinents over geological time. Pangaea is the most famous example, but the hypothetical version here is a world in which today’s continents are joined into one enormous landmass.
The interior problem
Moisture from oceans tends to fall as precipitation before air can travel thousands of kilometres inland. A gigantic continent would therefore create vast regions with strongly seasonal rainfall and potentially extensive deserts.
Coasts versus the middle
Coastal climates would still be moderated by nearby water, while the interior could experience larger temperature swings. The exact pattern would depend on latitude, mountains and ocean currents.
Ocean circulation
Joining continents would reshape the basins through which currents flow. That would alter where warm and cold water travel and could reorganize regional climates far from the new supercontinent.
Biodiversity
A giant landmass could allow some species to spread across areas that are currently separated by oceans. At the same time, new mountains, deserts and climate barriers could isolate populations and promote speciation.
Established scienceSupercontinents have existed in Earth’s past. The exact climate of a future single-continent Earth is model-dependent because geography, atmospheric composition and the location of the supercontinent all matter.
Human civilization
Ports and coastal cities would remain important, but long-distance overland transport could become more prominent. Food production would also be constrained by the large dry interiors and by major shifts in rainfall.
The bottom line
One giant continent would not make the whole planet uniformly dry. Instead it would create sharper contrasts between coastal and interior environments and reorganize ocean circulation, ecosystems and human geography.
A note on our approach: Every article on WhatIfLab separates what current science establishes from what remains genuinely speculative. Where we cite a figure or finding, it reflects published, mainstream research at the time of writing — not a prediction dressed up as fact.