There are two main problems with the original sentence.
(1) The subject (thousands of acres, which is plural) does not agree with the verb (is, which is singular and should be replaced with the plural are). Some students argue thatland is singular, even if it is thousands of acres. While land is singular, the phrase of pristine land is not the subject, but rather a prepositional phrase that describes the subject thousands of acres, which is plural.
(2) in danger to is not idiomatically correct and should instead be in danger of
A. The subject (thousands of acres, which is plural) does not agree with the verb (is, which is singular); in danger to is not idiomatically correct
B. The subject (thousands of acres, which is plural) agrees with the verb (are, which is plural); in danger of is idiomatically correct
C. The subject (thousands of acres, which is plural) does not agree with the verb (is, which is singular)
D. in danger to is not idiomatically correct
E. in danger for is not idiomatically correct