Can we? I'm not under the impression that those were ever terraced[1] like open-pit mines. But come to think of it, terracing itself qualifies as a megastructure[2]. Where the Long Now clock is an offbeat art project, rice paddies are crucial for nutrition for a great many people and they've already been around for at least 2 millenia. As times get lean, I can imagine pilfering the Long Now clock for parts; but those rice paddies will only gain importance.

[1] https://www.dreamstime.com/stock-photography-bingham-kenneco...

[2] https://en.wikipedia.org/wiki/Rice_Terraces_of_the_Philippin...