Final answer:
Paragraph 3 argues that carbon offsets are ineffective in the long run due to the destruction of natural carbon sinks for agriculture, leading to increased greenhouse gas emissions.
Step-by-step explanation:
In paragraph 3 of the text about why carbon offsets don't work long term, the author's main argument appears to be that carbon offsets are ineffective in the long run. This is suggested by the provided reference, which states that natural carbon sinks, which are crucial for offsetting emissions, are being destroyed for agricultural expansion. As a result, greenhouse gas emissions are increasing, indicating that carbon offsets cannot be a sustainable long-term solution to climate change if such practices continue.