Complex sentence: However, from around 1200 onwards, the climate became harsher--see Little Ice Age--and villages situated upon exposed uplands or upon clay vales where the soil became waterlogged bore the brunt of the changes.
Split into simpler sentences: However, from around 1200 onwards, the climate became harsher. Villages situated on exposed uplands or upon clay vales where the soil became waterlogged bore the brunt of the changes.