What trend? What is going on? What is the evidence? You've just seen empirical evidence to the contrary.
My first visit to Negril was in 1976. I walked the whole beach. I still walk the whole beach. I don't see any 'disturbing trend'. I've seen the sands go and then come back. If the waves and the wind are right, the sand gets pulled into the sea and settles off shore a little way out. Then the sea action brings it back in. Sometimes it shifts north, sometimes it shifts south. When the sand 'goes away', it doesn't evaporate, it's just off shore.
If there was a direct hit by a Cat 5 hurricane - then you would have something to worry about, but even then, over time, the beach would likely come back. I know, many people would believe 'we' caused the hurricane. I heard a guy on the radio the other day saying that humans caused earthquakes.
Why do people need to believe that 'we are destroying the planet'? What does that mean anyway? This planet will be here for another 4 billion years - until the sun goes supernova. Then it will be destroyed. We, on the other hand, will have disappeared several billions of years before that happens. We might not even be around for another 2,000 years. Given our current technology, we couldn't 'destroy' this planet - even if we wanted to.
So, chill out people, stop proselytizing. Have a Red Stripe, stop worrying, take a walk on the beach. Enjoy life.