qacwac- It's unfortunate people are too unbelieving to believe you, but some of us know you're right.
Off the spiritual record, though, assuming things just continue on without divine intervention, it will be our incredible loss of biodiversity.
We're witnessing the 6th great extinction, folks. The loss of biodiversity is like the snowball effect. When one thing goes extinct, it causes another to go extinct, which causes another, which could cause 2 more, which could cause 4 more, and on and on.. They say that we're up to 12 species(including microbial) a day. That in itself is an incredible lost resource. Nearly all, if not all, of our drugs and medicines, have roots in nature. We haven't even begun to break the surface of most organisms out there, esecially microbial. We haven't even found all the insects on the planet, believe it or not.
A team of seven american scientists said in 1988 that the loss of the Earth's biodiversity is a threat second only to thermonuclear war. They said by the year 2000 we will have lost around 33% of all biodiversity on the planet. I am not sure if that figure held up or not. They estimated that by the year 2050, we will have lost 66% of all biodiversity on the planet. Any biology-type will know that this is an absolute disaster.
So yeah, what Hominid said, our own ignorance/stupidity.