Final answer:
Without the imported dung beetles, Australia would have faced environmental issues due to dung accumulation, including increased pest populations, health issues for livestock, and poorer soil quality affecting plant growth and biodiversity.
Step-by-step explanation:
If Australia had not imported nonnative dung beetles to help clean up the dung produced by millions of nonnative cattle, there would likely have been significant environmental consequences. Without dung beetles to bury and consume cattle dung, accumulation of dung would have led to increased levels of pests like flies, potentially causing health issues for livestock and impacting the agricultural economy. Moreover, the lack of dung decomposition would have resulted in impaired nutrient recycling and poorer soil structure, negatively affecting plant growth and biodiversity.