Arable means capable of producing crops. arable land; arable soil. Not arable crops.
A person might consider a type of food as their source of protein. However, an entire industry... it sounds odd, even if it's logically accurate.
The word "import" may be used as a noun, but there seem to be certain set phrases where it fits, or doesn't fit. Here "imports" would be better. "soy imports". Or switch to "import" as a verb instead.
length of sentence
There are too many details in one single sentence. It would be clearer if broken into multiple sentences. (by the way, what is your native language? just curious.)
Finally, here is a possible alternative wording.
The food industry is heavily reliant on certain crops which cannot be considered sustainable or environmentally responsible in the long term. Soybean harvests, which are damaging the rain forests in South America, are a (good example/prime example of this).