Among the given options, using plastic as packaging material leads to the accumulation of non-biodegradable waste. Plastics take hundreds of years to decompose, polluting land and water bodies and harming animals who ingest them. In contrast, practices like organic farming, tree plantation, and composting promote biodegradability and environmental balance. Hence, the increase in plastic usage by humans is the primary reason for the rise in non-biodegradable substances in the environment. The correct option is (C).