If I’ll assume thate your statement merely seeks to establish a causal claim between climate change and sea rise and disappearance(-ing)- then i’ll confidently say both option as disappearance, which is in a complete state) and disappearing(which is in itself an ongoing phase) are technically correct; the only problem is I don’t get what you wanted to put across- I see the comma in the statement. Both options are correct. in

the end. the comparison of the two options is misleading.