Human activity has had ________ on the natural balance of Earth's ecosystems.

Consider the scale of these impacts. For instance, deforestation leads to habitat loss, which affects biodiversity, while pollution can harm air, water, and soil quality, impacting organisms at multiple levels.

Evaluate the options provided: 'Only positive effects' is incorrect because human activities have caused both positive (e.g., conservation efforts) and negative effects. 'A negligible influence' and 'no effect' are also incorrect because the evidence shows that human activities have had profound and widespread impacts.