Final answer:
It is true that global warming and the melting of glaciers threaten food production by reducing seasonal water supplies used for irrigation, while also contributing to rising sea levels.
Step-by-step explanation:
Global temperature increases, indeed, cause glaciers to melt, threatening food production over time by reducing water flow in rivers that are used for irrigation during the dry season. This statement is true. As glaciers retreat due to rising temperatures, the summer meltwaters that they release diminish, leading to a sharp reduction in the seasonal water supplies critical for irrigation and local ecosystems. Furthermore, the resultant rise in sea levels due to meltwater from glaciers and thermal expansion compromises shorelines, reduces island sizes, threatens species, and can lead to the disappearance of entire islands.