[WP] Shaders take a long time to load when loading a scene

How can I improve shader load time on WP? These make are adding nearly 30 seconds to my scene load times on Windows Phone.

Long thread activation time (908 ms) for object RenderFX/Skybox (Shader)
Long thread activation time (3645 ms) for object Hidden/TerrainEngine/Details/Vertexlit (Shader)
Long thread activation time (6063 ms) for object Hidden/TerrainEngine/Details/WavingDoublePass (Shader)
WARNING: Shader
Unsupported: 'Hidden/TerrainEngine/Details/BillboardWavingDoublePass' - Pass '' shader state not supported
Long thread activation time (6461 ms) for object Hidden/TerrainEngine/Details/BillboardWavingDoublePass (Shader)
Long thread activation time (3990 ms) for object Hidden/TerrainEngine/Splatmap/Lightmap-AddPass (Shader)
Long thread activation time (4293 ms) for object Nature/Terrain/Diffuse (Shader)