Final answer:
The correct answer is option (A) Decreased agricultural productivity; a period of abundant harvest.
Step-by-step explanation:
The biggest consequence of the reduction in vegetative growth due to rising U.S. population is often seen as decreased agricultural productivity. This reduction leads to a number of problems, such as habitat destruction, decreased biodiversity, scarcity of resources like water and arable land, and increased pollution. These changes can ultimately limit the earth's carrying capacity, affecting both population and resource use. The phrase 'super-harvest period' would refer to a time of abundant harvest.
However, when considering the consequences of increased human population and reduced vegetative growth, the concept of a super-harvest period seems contrary, as the impacts suggest a period of diminished, rather than abundant, harvest.
Hence, the correct answer to the question is (A) Decreased agricultural productivity; a period of abundant harvest. However, it's important to note that while 'super-harvest period' implies abundance, the context provided indicates that such a period is unlikely to occur given the pressures on food production ecosystems.