Here are the reductions of the adverb clauses to present or past participle clauses:

1. **Opening his new business**, he has been working 16 hours a day.
2. **Turning off the lights** before I left the room.
3. **Herding his goats in the mountains**, he discovered the coffee plant.
4. **Marching into battle**, they ate a mixture of raw coffee beans and fat for extra energy.
5. **Meeting the film star** in person, I understood why she was so popular.
6. **Searching through all my pockets**, I found my keys.
7. **First brought to Europe**, the tomato was thought to be poisonous.
8. **Imported into Australia many years ago**, the rabbit has become a serious pest.
9. **Given enough information about the causes of global warming**, we started our report.
10. **Kept in hot weather**, farm animals can suffer from heat stress.
11. **Worried about the consequences of deforestation**, some farmers stopped burning trees to create farmland.
12. **Produced in huge amounts**, carbon dioxide causes air pollution and climate change.