Can someone help me with Pinewood furniture treatment?

I got some shelves made from some pinewood recycled from packaging boxes, so the wood is not really high grade, bit suits the application. My worry is that the wood won't last too long in the climate where I live- hot and humid. Secondly I have also heard that the soft wood is prone to white-ants and termite. Is there any treatment I can do on the shelves to make them last longer, any advise will be helpful.

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