The volunteers are cleaning the oil spill.
The oil spill is being cleaned (by the volunteers).
Exhaust fumes cause a lot of air pollution in cities.
A lot of air pollution in cities is caused by exhaust fumes.
Global warming will affect our lives more than we think.
Our lives will be affected by global warming more than we think.
Flash floods had destroyed the village before we could offer any help.
The village had been destroyed by flash floods before we could offer any help.
Governments will have phased out fossil fuels in a decade.
Fossil fuels will have been phased out in a decade (by governments)
The authorities will have forbidden poaching in two years.
Poaching will have been forbidden in two years (by the autorities).
The gardeners have been fighting the spread of the invasive tree.
The spread of the invasive tree has been fought by the gardeners.
Supermarkets overuse packaging.
Packaging is being overused by supermarkets.
The arsonist caused the forest fire.
The forest fire was caused by the arsonist.
The drought was killing many trees.
Many trees were being killed by the drought.
Renewable energies could eliminate air pollution.
Air pollution could be eliminated by renewable energies.
Deforestation will provoke loss of habitat for many species.
Loss of habitat for many species will be provoked by deforestation.