Some projects may be unlikely to have significant effects on their own but effects in combination with other plans or projects may be significant.
Mae’n bosibl y bydd rhai prosiectau’n annhebygol o gael effeithiau arwyddocaol ar eu pen eu hunain, ond fe allai’r effeithiau ar y cyd â chynlluniau neu brosiectau eraill fod yn arwyddocaol.