Which human activity contributes the most oil to the oceans?

The activity that contributes the most oil to the oceans is related to the pollution that occurs on land, particularly through runoff. When oil spills occur on land, either from spills, leaks, or improper disposal, rainfall can wash this oil into rivers and eventually into the oceans. This runoff is often a significant source of oil pollution, overshadowing the contributions from offshore oil drilling and transport.

Transporting oil over the ocean surface does indeed pose risks of spills, but the frequency and volume of oil introduced into marine environments via land runoff are substantial and often occur over broader areas and time frames. Therefore, while transporting oil can lead to localized spills, it does not represent the primary source of oil entering oceans when compared to the cumulative effects of land-based pollution.

In the context of assessing oil pollution in oceans, understanding the interconnectedness of land activities and how they lead to oceanic contamination is crucial for comprehending the larger environmental impacts.