Rising levels of carbon dioxide most likely have a greater detrimental effect on the land than the sea. have a greater detrimental effect on the sea than the land. can increase productivity on the land and the sea. can decrease productivity on the land and the sea.

The answer is;  can decrease productivity on the land and the sea.

When there is increased carbon dioxide in the atmosphere,  more carbon dioxide Is dissolved by the seas. This increases the pH levels of the water of the sea. Increase in pH causes coral bleaching  and hence decreases biodiversity in this ecosystem.

Also, on land, global warming (caused by greenhouse gases such as carbon dioxide) causes climate change. Climate change reduces the biodiversity of crops on land and hence reduces productivity including disadvantaging farmers that depend on farming for income.