Final answer:
Viruses have an environmental importance in terms of regulating bacterial populations.
Step-by-step explanation:
One environmental importance of viruses is regulation of bacterial populations. Viruses that infect bacteria, known as bacteriophages, can help control the abundance and diversity of bacterial populations in various ecosystems. Bacteriophages infect and reproduce within bacteria, leading to their destruction and subsequent release of nutrients into the environment. This process helps maintain the balance of microbial communities and nutrient cycling in ecosystems.