Which of the Following Examples Poses the Greatest Potential Threat

Which of the following examples poses the greatest potential threat to biodiversity?

A) replanting, after a clear cut, a monoculture of Douglas fir trees on land that consisted of old-growth Douglas fir, western cedar, and western hemlock
B) allowing previously used farmland to go fallow and begin to fill in with weeds and then shrubs and saplings
C) lack of regulations to limit the harvest of the medicinal plant ginseng
D) constructing oil and gas pipelines through old growth forest