Which of the following most logically completes the passage?
A tropical thorn forest was cleared and converted by humans into soybean fields. The loss of the original habitat poses a threat to the area's population of cuis, which are wild guinea pigs. Ecologists originally estimated that the cuis in the area would vanish within four years. Two years later, the population of cuis is already cut in half, but it is unlikely that they will completely vanish from the region within the next two years,