Not strictly accurate; it's the major part of it, but climate-change driven species loss is a real threat and at some point will likely outpace the rate of loss due to land/resource exploitation.
Ocean biodiversity loss is almost certainly harmed by overfishing and toxic run-off from rivers/lakes don't get me wrong, but it's also hugely impacted by rising sea temperatures. Ocean biodiversity increases exponentially with sea surface temperature up to about 20-25 C (68-77 F). Beyond that threshold, biodiversity drops off due to the limits of aerobic metabolism. Temperatures that make it hard for cold-blooded sea creatures to breathe have likely been among the biggest drivers for shifts in the distribution of marine biodiversity.
Desertification, caused partly by human agriculture and the removal of soil-retaining plant matter but mostly due to climate change, is also a major cause of species loss and it's occurring across much of the planet - especially Africa and Central Asia. Those animals that can't rapidly migrate to cooler/wetter climates are ripe for extinction.