The collapse of fisheries worldwide, soil degradation across nearly all arable land currently in use, broad ecosystem collapse (see decreasing numbers of insects worldwide). All of these are signs of unsustainable use of the planet's resources. Hell, absent fertilizers from fossil fuels, the green revolution (and subsequent population boom) wouldn't be possible.

There are too many people living living lives that consume too many resources currently. While we've slowed our growth, we're going to shrink our resource utilization absent extra capacity from space. That reduction will either be managed or unmanaged reduction (e.g. collapse).