Does a creature that becomes a land retain its creature types and abilities?

When a spell or ability causes a permanent to 'become a land,' the result depends on the exact wording. If the effect says a permanent 'becomes a basic land' or 'is a land' without specifying it retains its other types, it typically loses all previous card types, subtypes, and abilities, replacing them with those of the new land type. This is governed by CR 305.7 and the layer system in CR 613.

The layer system (CR 613.1) determines how type-changing effects interact. Type-changing effects apply in Layer 4. If an effect simply sets a permanent's type to 'land' (removing 'creature'), then in that same layer the creature types and subtypes are lost. Abilities granted by the card's own rules text are also removed because the card's text no longer applies as a creature — this is addressed by CR 612.1, which handles text-changing and type-setting effects.

However, if an effect says a creature 'becomes a land in addition to its other types,' it retains all creature types, power/toughness, and abilities. This additive phrasing is crucial. CR 305.7 specifically notes that a land may also be other card types.

Concrete example: If your opponent casts Sanguine Indulgence-style effect turning your Grizzly Bears into a basic Forest, the Bears loses its 'Bear' creature type, its 2/2 power/toughness, and all abilities — it is simply a Forest that taps for green mana. Conversely, Awaken effects (e.g., from Scatter to the Winds) make a land a creature in addition, so the land keeps its land abilities while gaining creature properties.

In summary: check whether the effect replaces the permanent's types entirely or adds to them. Complete replacement (CR 613.1d) strips creature types and abilities; additive effects preserve them.