Research fossil fuels.
Build tidal power harnesser.
Build levee for a fish farm, so that we can have clean fish.
Build public transport system.
Pass Legislation:
All fossil fuel powered vehicles are required to have catalytic converters. Reduces pollution from vehicles.
Place a 8% fuel tax on all fossil fuels going to vehicles. Reduces pollution from vehicles.
Place a 2% tax refund on all clean fuels. Reduces pollution.
Start a civil defense program. This educates civilians on how to protect themselves from air raids, atomic attacks, and how to properly evacuate and ensure your survival in the event of an attack or a natural disaster.
Begin a national recycling program. Reduces pollution, re-uses limited materials.
Diplomacy:
Offer DK a defensive pact.